Kin Ho Lo

Abstract The sluggish oxygen evolution reaction (OER) is a pivotal process for renewable energy technologies, such as water splitting. The discovery of efficient, durable, and earth‐abundant electrocatalysts for water oxidation is highly desirable. Here, a novel trimetallic nitride compound grown on nickel foam (CoVFeN @ NF) is demonstrated, which is an ultra‐highly active OER electrocatalyst that outperforms the benchmark catalyst, RuO 2 , and most of the state‐of‐the‐art 3D transition metals and their compounds. CoVFeN @ NF exhibits ultralow OER overpotentials of 212 and 264 mV at 10 and 100 mA cm −2 in 1 m KOH, respectively, together with a small Tafel slop of 34.8 mV dec −1 . Structural characterization reveals that the excellent catalytic activity mainly originates from: 1) formation of oxyhydroxide species on the surface of the catalyst due to surface reconstruction and phase transition, 2) promoted oxygen evolution possibly activated by peroxo‐like (O 2 2− ) species through a combined lattice‐oxygen‐oxidation and adsorbate escape mechanism, 3) an optimized electronic structure and local coordination environment owing to the synergistic effect of the multimetal system, and 4) greatly accelerated electron transfer as a result of nitridation. This study provides a simple approach to rationally design cost‐efficient and highly catalytic multimetal compound systems as OER catalysts for electrochemical energy devices.

Abstract As one of the most important chemicals and an energy carrier, synthetic ammonia has been widely studied to meet the increasing demand. Among various strategies, electrochemical nitrogen reduction reaction (e‐NRR) is a promising way because of its green nature and easy set‐up on large‐scale. However, its practical application is extremely limited because of the very‐low production rate, which is strongly dependent on the electrocatalysts used. Therefore, searching novel efficient electrocatalysts for e‐NRR is essential to promote the technology. In this review, it highlights the insights on the mechanism for the NH 3 electrochemical synthesis, recommend a reliable protocol for the ammonia detection, and systematically summarize the recent development on novel electrocatalysts, including noble metal‐based materials, single‐metal‐atom catalysts, non‐noble metal, and their compounds, and metal‐free materials, for efficient e‐NRR in both experimental and theoretical studies. Various strategies to improve the catalytic performance by increasing exposed active sites or tuning electronic structures, including surface control, defect engineering, and hybridization, are carefully discussed. Finally, perspectives and challenges are outlined. It can be expected that this review provides insightful guidance on the development of advanced catalytic systems to produce ammonia through N 2 reduction.

Abstract Hydrogen evolution reaction (HER) is a key step for electrochemical energy conversion and storage. Developing well defined nanostructures as noble‐metal‐free electrocatalysts for HER is promising for the application of hydrogen technology. Herein, it is reported that 3D porous hierarchical CoNiP/Co x P multi‐phase heterostructure on Ni foam via an electrodeposition method followed by phosphorization exhibits ultra‐highly catalytic activity for HER. The optimized CoNiP/Co x P multi‐phase heterostructure achieves an excellent HER performance with an ultralow overpotential of 36 mV at 10 mA cm −2 , superior to commercial Pt/C. Importantly, the multi‐phase heterostructure shows exceptional stability as confirmed by the long‐term potential cycles (30,000 cycles) and extended electrocatalysis (up to 500 h) in alkaline solution and natural seawater. Experimental characterizations and DFT calculations demonstrate that the strong electronic interaction at the heterointerface of CoNiP/CoP is achieved via the electron transfer from CoNiP to the heterointerface, which directly promotes the dissociation of water at heterointerface and desorption of hydrogen on CoNiP. These findings may provide deep understanding on the HER mechanism of heterostructure electrocatalysts and guidance on the design of earth‐abundant, cost‐effective electrocatalysts with superior HER activity for practical applications.

Design and synthesis of noble-metal-free bifunctional catalysts for efficient and robust electrochemical water splitting are of significant importance in developing clean and renewable energy sources for sustainable energy consumption. Herein, a simple three-step strategy is reported to construct cobalt-iron nitride/alloy nanosheets on nickel foam (CoFe-NA/NF) as a bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The electrocatalyst with optimized composition (CoFe-NA2/NF) can achieve ultralow overpotentials of 73 mV and 250 mV for HER and OER, respectively, at a current density of 10 mA cm−2 in 1 M KOH. Notably, the electrolyzer based on this electrocatalyst is able to boost the overall water splitting with a cell voltage of 1.564 V to deliver 10 mA cm−2 for at least 50 h without obvious performance decay. Furthermore, our experiment and theoretical calculation demonstrate that the combination of cobalt-iron nitride and alloy can have low hydrogen adsorption energy and facilitate water dissociation during HER. In addition, the surface reconstruction introduces metal oxyhydroxides to optimize the OER process. Our work may pave a new pathway to design bifunctional catalysts for overall water splitting.

Perovskite oxides are studied as electrocatalysts for oxygen evolution reactions (OER) because of their low cost, tunable structure, high stability, and good catalytic activity. However, there are two main challenges for most perovskite oxides to be efficient in OER, namely less active sites and low electrical conductivity, leading to limited catalytic performance. To overcome these intrinsic obstacles, various strategies are developed to enhance their catalytic activities in OER. In this review, the recent developments of these strategies is comprehensively summarized and systematically discussed, including composition engineering, crystal facet control, morphology modulation, defect engineering, and hybridization. Finally, perspectives on the design of perovskite oxide-based electrocatalysts for practical applications in OER are given.

Abstract Ammonia as an irreplaceable chemical has been widely demanded to keep the sustainable development of the modern society. However, its industrial production consumes huge energy and releases extraordinary green‐house gases, leading to various environmental issues. To achieve the green production of ammonia is a great challenge that has been extensively pursued recently. In the review, a most promising strategy, electrochemical nitrate reduction reaction (e‐NO 3 RR) for the purpose is comprehensively investigated to give a full understanding of its development and mechanism and provide guidance for future directions. Particularly, the development of electrocatalysts is focused to realize the high ammonia yield rate and Faraday efficiency for industrial applications. The recent‐developed catalysts, including noble metallic materials, alloys, metal compounds, single‐metal‐atom catalysts, and metal‐free materials, are systematically discussed to review the effects of various factors on the catalytic performance in e‐NO 3 RR. Accordingly, the strategies, including defects engineering, coordination environment modulating, surface controlling, and hybridization, are carefully discussed to improve the catalytic performance, such as the intrinsic activity and selectivity. Finally, perspectives and challenges are given out. This review shall provide insightful guidance on the development of advanced catalytic systems for the production of green ammonia efficiently in the industry.

Predicted spin–valley coupling and valley polarization in two-dimensional MoSi₂X₄ (X = N, P, and As).

Spin state of Co 3+ ion transfers from low spin (LS: t62ge0g) to high spin (HS: t42ge2g) under strain engineering. HS CoOOH is much active for OER, because of small O 2 release energy (0.03 eV) and effective directly O–O bond coupling (1.21 eV).

In this community review report, we discuss applications and techniques for fast machine learning (ML) in science-the concept of integrating powerful ML methods into the real-time experimental data processing loop to accelerate scientific discovery. The material for the report builds on two workshops held by the Fast ML for Science community and covers three main areas: applications for fast ML across a number of scientific domains; techniques for training and implementing performant and resource-efficient ML algorithms; and computing architectures, platforms, and technologies for deploying these algorithms. We also present overlapping challenges across the multiple scientific domains where common solutions can be found. This community report is intended to give plenty of examples and inspiration for scientific discovery through integrated and accelerated ML solutions. This is followed by a high-level overview and organization of technical advances, including an abundance of pointers to source material, which can enable these breakthroughs.

Massively converting nitrogen gas to ammonia is a key process in modern agricultural and industrial fields. The conventional Haber–Bosch process for NH3 production has to be carried out under extreme conditions, leading to high energy consumption and huge emission of greenhouse gases. Electrochemical N2 reduction is a promising way for NH3 production due to its sustainable process and feasibility in an ambient environment. In this work, we screen the transition metals (TM), including 26 elements, supported on two-dimensional (2D) Nb2CN2 (TM-Nb2CN2) for their applications in the electrochemical reduction of N2 (NRR) based on first-principles calculations. We show that most SACs can bind with Nb2CN2 strongly through a TM-3N configuration. We find that Mn-Nb2CN2 is a promising candidate for the N2 reduction reaction (NRR), with a low overpotential of 0.51 V through the distal mechanism. Importantly, TM-Nb2CN2 presents high selectivity to NRR by blocking the hydrogen adsorption and preventing the hydrogen evolution reaction. Moreover, the scaling relationship and Bader charge analysis provide an insightful understanding of the mechanism for NRR on single-atom catalysts (SACs) anchored on 2D MXenes. Our findings may guide the design of novel substrates for SACs with effectively improved performance.

Abstract The surface‐enhanced Raman scattering (SERS) as a novel and efficient analytic technique to probe molecules has attracted tremendous attention. Semiconducting substrates have been widely investigated for their applications into SERS because of their easy integration with electronic devices. In this work, a wafer‐scale semiconducting MoS 2 monolayer (2H‐MoS 2 ‐ML) without additional treatment is used as the SERS substrate, which shows the naturally formed MoS 2 ML has excellent chemical stability, high uniformity, and high sensitivity. It is found that the detection concentration limit can reach 1 × 10 −8 m and the enhancement factor is about 4.5 × 10 6 for the rhodamine 6G (R6G) under a 532 nm excitation laser, which is the highest SERS performance observed on 2H‐MoS 2 ‐ML up to now. The experimental and computational studies reveal that the photo‐enhanced charge transfer coupled with molecule resonance contribute to remarkable SERS. In addition to R6G, 2H‐MoS 2 ‐ML shows good SERS signals on the detection of amaranth and crystal violet too. The findings not only provide an insightful understanding of the mechanism for the improved SERS performance of semiconducting transition‐metal dichalcogenides (TMDs) MLs, but are helpful for the design of novel SERS substrates. It is expected that the wafer‐scale TMDs may find practical applications in SERS.

The transition-metal (oxy)hydroxides have been considered as one of the promising electrocatalysts for oxygen evolution reaction (OER). Therefore, it is necessary to have in-depth study on the origin behind their favorable inherent OER activity and further improve their catalytic performance. Herein, nickel–cobalt-vanadium trimetallic (oxy)hydroxide nanosheets decorated with silver nanoparticles (Ag NPs) ([email protected]0.2Co0.2) are fabricated for OER by a simple spontaneous redox reaction. The [email protected]0.2Co0.2 can deliver an overpotential of only 255 mV at 10 mA cm−2 and a small Tafel slope of 38.3 mV dec-1 in alkaline solution. We accredit the outstanding catalytic performance to the following aspects: (1) the active (oxy)hydroxide layer on the surface of [email protected]0.2Co0.2 generated through the surface reconstruction, (2) the optimal local coordination induced by the interaction between Ag NPs and trimetallic system, (3) the extensively exposed active sites, and (4) the significantly improved charge-transfer ability due to the incorporation of Ag NPs. Our findings may provide deep understanding on the mechanism of OER and offers a novel strategy to design electrocatalysts with superior OER activity.

Understanding the mechanism of tricalcium silicate (C3S) hydration is significant for controlling the process of cement hydration. In this work, the adsorption mechanism of water on the C3S surface is revealed from first-principles calculations. We find: (1) the adsorption energy increases with the increase of electron transfer at water/C3S interface and strength of total Ca-Ow bonds; (2) the mechanism of adsorption of water on C3S surfaces is due to the electron transfer from VBM of C3S surface to LUMO of water molecule, raising the Fermi level and shifting the bonding molecular orbital downward; (3) the water becomes more structured and motionless as being closer to the surface; and (4) The stability of the dissociative and molecular adsorption is reverse for isolated and bulk water due to the different reaction pathways. Our findings may shed light on the fundamental understanding for the initial stage of C3S hydration.

Low-cost and efficient electrocatalysts have been extensively studied for hydrogen evolution reaction (HER) in large-scale hydrogen production. However, the actual active sites on their surfaces in working condition have not been understood clearly. Herein, we carry out a systematic study to figure out the active sites on the Ni/NixP hybrids grown on carbon cloth (Ni/NixP/CC) for HER in both acidic and alkaline conditions, by a series of combined in-situ and ex-situ characterizations. Interestingly, we find that their current densities gradually increase (maximum: 106.1%) at a voltage of −0.16 V (vs. RHE) in acid, but show slight reduction in alkali at a voltage of −0.2 V (vs. RHE). Ex-situ studies show that Ni/NixP/CC electrodes undergo significant morphology remodeling and surface reconstruction after working in both acid and alkali. However, in-situ Raman spectroscopy shows that the surface reconstruction does not happen during the HER process. Most importantly, in-situ Raman spectroscopy reveals that the negatively charged P ions act as active sites that attract the positively charged protons for HER. Our findings demonstrate that tracking the dynamic structure evolution may be significant to gain insightful understanding on the reaction mechanism, which shall provide meaningful guidance to the design of catalysts for practical applications.

Two-dimensional carbon nitride (2DCN) materials have emerged as an important class of 2D materials beyond graphene. However, 2DCN materials with nodal-line semimetal characteristic are rarely reported. In this work, a new nodal-line semimetal 2DCN with the stoichiometry C4 N4 is designed by using density functional theory (DFT) calculations and its application to anchor single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) is investigated. C4 N4 is a planar covalent network (sp2 hybridization) with regular holes formed by the four N atoms, which is dynamically, thermodynamically, and mechanically stable. The nodal line is contributed by the pz orbitals of C and px/y orbitals of N atoms. C4 N4 shows an anisotropic Fermi velocity and high electron mobility. Because of its porous structure, C4 N4 can anchor heteroatoms as SACs for electrocatalysis. C4 N4 anchored with Fe or Co is shown to be highly active for the ORR with a rather high half-wave potential of around 0.90 V, which is higher than those of SACs on other carbon nitrides. These findings may provide a new strategy to design novel substrates for SACs.

For most promising SACs, the selectivity for e-NRR improves on increasing the curvature.

SmallVolume 17, Issue 43 2170226 Inside Back CoverFree Access Development of Perovskite Oxide-Based Electrocatalysts for Oxygen Evolution Reaction (Small 43/2021) Dong Liu, Dong Liu Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorPengfei Zhou, Pengfei Zhou Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorHaoyun Bai, Haoyun Bai Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorHaoqiang Ai, Haoqiang Ai Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorXinyu Du, Xinyu Du Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorMingpeng Chen, Mingpeng Chen Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorDi Liu, Di Liu Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorWeng Fai Ip, Weng Fai Ip Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorKin Ho Lo, Kin Ho Lo Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorChi Tat Kwok, Chi Tat Kwok Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorShi Chen, Shi Chen Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorShuangpeng Wang, Shuangpeng Wang Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorGuichuan Xing, Guichuan Xing Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorXuesen Wang, Xuesen Wang Department of Physics, National University of Singapore, Singapore, 117542 SingaporeSearch for more papers by this authorHui Pan, Hui Pan Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 China Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this author Dong Liu, Dong Liu Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorPengfei Zhou, Pengfei Zhou Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorHaoyun Bai, Haoyun Bai Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorHaoqiang Ai, Haoqiang Ai Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorXinyu Du, Xinyu Du Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorMingpeng Chen, Mingpeng Chen Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorDi Liu, Di Liu Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorWeng Fai Ip, Weng Fai Ip Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorKin Ho Lo, Kin Ho Lo Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorChi Tat Kwok, Chi Tat Kwok Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorShi Chen, Shi Chen Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorShuangpeng Wang, Shuangpeng Wang Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorGuichuan Xing, Guichuan Xing Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this authorXuesen Wang, Xuesen Wang Department of Physics, National University of Singapore, Singapore, 117542 SingaporeSearch for more papers by this authorHui Pan, Hui Pan Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 China Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Taipa, Macao SAR, 999078 ChinaSearch for more papers by this author First published: 27 October 2021 https://doi.org/10.1002/smll.202170226Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Perovskite Oxide-Based Electrocatalysts In article number 2101605, Shi Chen, Shuangpeng Wang, Guichuan Xing, Hui Pan, and co-workers systematically summarize perovskite oxides as electrocatalysts for efficient oxygen evolution reaction (OER). The catalytic mechanism and descriptors for perovskite oxides are also discussed in detail. Additionally, various strategies to improve the OER catalytic performance of perovskite oxides are carefully reviewed, including composition engineering, crystal facet control, morphology modulation, defect engineering, and hybridization. Citing Literature Volume17, Issue43Special Issue: 40th Anniversary of University of MacauOctober 27, 20212170226 RelatedInformation

Novel 2D materials (MSi₂C_xN_4−x) with tunable electronic and magnetic properties.

Photoelectrochemical Water Oxidation In article number 2304376, Kin Ho Lo, Hui Pan, and co-workers report a metal-insulator-semiconductor (MIS) structure photoanode (n-Si/SiOx/CoOx-Mo) to show a high photovoltage of 650 mV, saturation current density of 27.6 mA cm−2, and fill factor of 0.62 in 1.0 M K3BO3 because the energy barrier, charge transfer, reaction kinetics, and active sites are dramatically increased by the Mo-incorporation. And the Mo-incorporated photoanode is also highly stable.

A two-step transition in the magnetic state occurs in bilayer TiI₃ under applied strain.

A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$, recorded with the CMS detector. The coupling strength with respect to the standard model value, $Y_\mathrm{t}$, is determined from kinematic distributions in $\mathrm{t\bar{t}}$ final states containing ee, $μμ$, or e$μ$ pairs. Variations of the Yukawa coupling strength lead to modified distributions for $\mathrm{t\bar{t}}$ production. In particular, the distributions of the mass of the $\mathrm{t\bar{t}}$ system and the rapidity difference of the top quark and antiquark are sensitive to the value of $Y_\mathrm{t}$. The measurement yields a best fit value of $Y_\mathrm{t} =$ 1.16 $^{+0.24}_{-0.35}$, bounding $Y_\mathrm{t}$ $\lt$ 1.54 at a 95% confidence level.

Ferroelectrics is expected to be an alternative to traditional solar cells, because its bulk photovoltaic effect (BPVE) may overcome the Shockley–Queisser limit. Here, we propose that a family of polar materials without centrosymmetry, distorted 1T (1T′′′) transition-metal dichalcogenides, shows a large BPVE in the infrared and visible light due to their moderate band gaps based on density-functional-theory (DFT) calculations. We find that the BPVEs in bulks are much higher than those in monolayers because of the smaller band gaps and more delocalized valence band states. We further show that strain engineering serves as an efficient strategy to enhance the BPVE of 1T′′′-MoS2 bulk. The shift-current responses in the bulks spotlight their potential for applications into solar energy harvesting. This work provides the theoretical evidence of BPVE in 1T′′′ transition-metal dichalcogenides and guidance on the design of novel materials with an enhanced BPVE for green-energy technologies.

A new family of 2D materials with a chemical formula of M₃C₆N₂ (MCNs) were predicted, which show ultrasoft mechanical, and diveral electronic and magnetic properties.

For control nets outlining a large class of topological polyhedra, not just tensor-product grids, bi-cubic polyhedral splines form a piecewise polynomial, first-order differentiable space that associates one function with each vertex. Akin to tensor-product splines, the resulting smooth surface approximates the polyhedron. Admissible polyhedral control nets consist of quadrilateral faces in a grid-like layout, star-configuration where n ≠ 4 quadrilateral faces join around an interior vertex, n -gon configurations, where 2n quadrilaterals surround an n -gon, polar configurations where a cone of n triangles meeting at a vertex is surrounded by a ribbon of n quadrilaterals, and three types of T-junctions where two quad-strips merge into one. The bi-cubic pieces of a polyhedral spline have matching derivatives along their break lines, possibly after a known change of variables. The pieces are represented in Bernstein-Bézier form with coefficients depending linearly on the polyhedral control net, so that evaluation, differentiation, integration, moments, and so on, are no more costly than for standard tensor-product splines. Bi-cubic polyhedral splines can be used both to model geometry and for computing functions on the geometry. Although polyhedral splines do not offer nested refinement by refinement of the control net, polyhedral splines support engineering analysis of curved smooth objects. Coarse nets typically suffice since the splines efficiently model curved features. Algorithm 1032 is a C++ library with input-output example pairs and an IGES output choice.

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$γγ$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvertζ_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvertζ_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.

Preciptation-hardenable (PH) stainless steels are widely employed in industry for their high mechanical strength, reasonable toughness and moderate corrosion resistance. In the present study, laser surface melting of 17-4 PH precipitation-hardenable stainless steel (Fe-17%Cr-4%Ni-4%Cu-0.3%Nb) was attempted using a 2.5-kW continuous wave Nd:YAG laser for enhancing its corrosion resistance and hardness. The pitting corrosion behavior of laser surface-melted samples processed under different processing conditions in 3.5% NaCl solution at 25 °C was studied by open circuit potential measurement and potentiodynamic polarization technique. Compared with the annealed and aged 17-4 PH, the corrosion resistance of the laser surface-melted samples was significantly improved, as evidenced by a noble shift in open circuit potential, a higher pitting potential, a wider passive range and a lower passive current density. The enhanced corrosion resistance was attributed to the refinement of precipitation of copper particles in the ferrite matrix. In addition, the hardness of the laser surface-melted 17-4 PH was found to be higher than that of the aged and annealed ones by 14% and 27% respectively.

In article number 2002464, Shi Chen, Lei Wang, Guichuan Xing, Hui Pan and co-workers develop a vanadium-cobalt-iron trimetal nitride system with greatly enhanced electrocatalytic activity for the oxygen evolution reaction (OER). The metal oxyhydroxide formed in the OER process due to the surface reconstruction and phase transition is the intrinsic active species for the OER. In addition, the promoted oxygen evolution is possibly activated by a peroxo-like (O22−) species through a combined lattice-oxygen-oxidation and adsorbate-escape mechanism.

This chapter reviews laser surface melting (LSM) of aged stainless steels for mitigating intergranular corrosion (IGC) by various researchers. In addition, the effect of LSM on IGC behavior of aged austenitic stainless steels (UNS S30400, S34700 and FeCrMn) and aged duplex stainless steels (UNS S31803 and S32760) is investigated.

Abstract Carbon neutrality has drawn increasing attention for realizing the carbon cyclization and reducing the greenhouse effect. Although the C1 products, such as CO, can be achieved with a high Faraday efficiency, the targeted production of C2 fuels as well as the mechanism have not been systematically investigated. In this work, we carry out a first‐principles study to screen dual‐atom catalysts (DACs) for producing C2 fuels through the electrocatalytic carbon monoxide reduction reaction (e‐CORR). We find that methanol, ethanol and ethylene can be produced on both DAC−Co and DAC−Cu, while acetate can be achieved on DAC−Cu only. Importantly, methanol and ethylene are preferred on DAC−Co, while acetate and ethylene on DAC−Cu. Furthermore, we show that the explicit solvent can enhance the adsorption and influence the protonation steps, which subsequently affects the protonation and dimerization behavior as well as the performance and selectivity of e‐CORR on DACs. We further demonstrate that the C−C coupling is easy to be formed and stabilized if the Integrated Crystal Orbital Hamilton Population (ICOHP) is low because of the low energy barrier. Our findings provide not only guidance on the design of novel catalysts for e‐CORR, but an insightful understanding on the reduction mechanism.

Green hydrogen is considered to be the key for solving the emerging energy and environmental issues. The photoelectrochemical (PEC) process for the production of green hydrogen has been widely investigated because solar power is clean and renewable. However, mass production in this way is still far away from reality. Here, a Si photoanode is reported with CoOx as co-catalyst for efficient water oxidation. It is found that a high photovoltage of 350 mV can be achieved in 1.0 m K3 BO3 . Importantly, the photovoltage can be further increased to 650 mV and the fill factor of 0.62 is obtained in 1.0 m K3 BO3 by incorporating Mo into CoOx . The Mo-incorporated photoanode is also highly stable. It is shown that the incorporation of Mo can reduce the particle size of co-catalyst on the Si surface, improve the particle-distribution uniformity, and increase the density of particles, which can effectively enhance the light absorption and the electrochemical active surface area. Importantly, the Mo-incorporation results in high energy barrier in the heterojunction. All of these factors are attributed to improved the PEC performance. These findings may provide new strategies to maximize the solar-to-fuel efficiency by tuning the co-catalysts on the Si surface.

[This corrects the article DOI: 10.3389/fdata.2022.787421.].

2D materials have been interesting for applications into nanodevices due to their intriguing physical properties. In this work, four types of unique structures are designed that are composed of MXenes and C/N-Si layers (CNSi), where MXene is sandwiched by the CNSi layers with different thicknesses, for their practical applications into integrated devices. The systematic calculations on their elastic constants, phonon dispersions, and thermodynamic properties show that these structures are stable, depending on the composition of MXene. It is found: 1) different from MXene or N-functionalized MXene (M2 CN2 ), SiN2 /M2 X/SiN2 possess new electronic properties with free carriers only in the middle, leading to 2D free electron gas; 2) CNSi/MXene/CNSi shows an intrinsic Ohmic semiconductor-metal-semiconductor (S-M-S) contact, which is potential for applications into nanodevices; and 3) O/M2 C/SiN2 and N/M2 C/OSiN are also stable and show different electronic properties, which can be semiconductor or metal as a whole depending on the interface. A method is further proposed to fabricate the 2D structures based on the industrial availability. The findings may provide a novel strategy to design and fabricate the 2D structures for their application into nanodevices and integrated circuits.

A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016-2018, corresponding to an integrated luminosity of 117 fb$^{-1}$. The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H $\to$ SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10-100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass ($\approx$15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions $\mathcal{B}$(H $\to$ SS) $\lt$ 20% for proper decay lengths of 10-50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.

A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13\TeV is presented. The transverse momenta of jets within $\lvert\eta\rvert \lt$ 4.7 reach down to 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background.

In the present study, microstructural evolution and hardness of the friction stir processed (FSPed) SAF 2507 super duplex stainless steel fabricated at a rotational speed of 650 rpm and a traverse speed of 60 mm/min were investigated. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to study the microstructure of the stir zone. The grain sizes of austenite and ferrite in the FSPed 2507 were found to be smaller (0.75 and 0.96 μm) than those of the substrate (6.6 and 5.6 μm) attributed to the occurrence of continuous dynamic recrystallization (CDRX) in both phases. Higher degree of grain refinement and DRX were obtained at the advancing side of the FSPed specimens due to higher strain and temperature. A non-uniform hardness distribution was observed along the longitudinal direction of the SZ. The maximum hardness was obtained at the bottom (407 HV1).

Abstract This chapter discusses the compositions, mechanical properties, phase structure, stabilization, corrosion resistance, and advantages of austenitic stainless steels. Austenitic alloys are classified and reviewed in three groups: (1) lean alloys, such as 201 and 301, which are generally used when high strength or high formability is the main objective; (2) chromium nickel alloys used for high temperature oxidation resistance; and (3) chromium, molybdenum, nickel, and nitrogen alloys used for applications where corrosion resistance is the main objective.

This chapter is on ferritic stainless steels. A brief introduction to the compositions and uses of the various grades of steels in the ferritic class is given. New techniques for grain refinement of the ferritic class are presented. The main problems plaguing the ferritic class, i.e., 475°C-embrittlement, formation of sigma phase and sensitisation, are discussed, with reference to the constitution diagram of the Fe-Cr system. The various theories proposed for the causes of these problems, together with the old and new methods for their alleviation/elimination, are presented in detail.

Sensitization is one of the corrosion mechanisms which cause widespread problems in stainless steels, particularly in welded assemblies and improperly heat-treated work pieces heated at 500 to 800°C. As the Cr-rich carbides and sigma phase form, they deplete their neighboring regions of Cr, thereby lowering the Cr contents of the surface oxides over these regions. Once the contents of Cr in the regions adjacent to the carbides drop below 12 wt%, the oxide layers lose their protectiveness. Then the stainless steels will suffer from intergranular corrosion attack. Laser surface melting (LSM) can be easily achieved by melting the surface with a laser beam followed by rapid solidification for homogenizing chemical compositions, desensitization of improperly heated surface (i.e. redisolving the chromium carbides) and even removing surface cracks. In the present study, LSM of austenitic stainless steels (AISI 304, 321 and 347) and duplex stainless steel (AISI 2205) was attempted for desensitization by a 2.5 kW Nd:YAG laser and the susceptibility of the sensitized stainless steels before and after LSM to intergranular corrosion was also evaluated. The degree of sensitisation (DOS) of the stainless steels was determined by the double loop electrochemical potentio-kinetic reactivation method in solution of 0.5 M H2SO4 and 0.01 M KSCN at 25 °C by a potentiostat. The corrosion morphology and surface hardness were also investigated as well. Desensitization of stainless steels was successfully achieved by LSM and their intergranular corrosion resistance was found to be significantly enhanced as reflected by the decrease in DOS due to the low chromium depletion or possible solute segregation at the boundaries.

This article gives an overview of several new, patented (proprietary) carburising and nitriding techniques. The SAT12 process, developed by Swagelok Company, and the Kolsterising process are carburising methods that may give rise to colossal carbon supersaturation to the surface layer of austenitic stainless steels, resulting in substantial improvement to mechanical and corrosion properties. A newly-invented, patented nitriding technique for achieving colossal nitrogen content in the surface layer of austenitic stainless steel is introduced in this article, too. One of the weaknesses of conventional carburization/nitriding techniques is the formation of carbides and nitrides. However, nearly no carbide/nitride/carbonitride precipitation takes place for the new carburising/nitriding techniques until very high C/N contents. Besides, very thick carburized/nitrided layers may be achieved with the new techniques. In addition to carburising and nitriding, a variety of novel, new, and potentially patentable surface enhancing methods (e.g., surface nanostructuring processes and laser surface treatment) are also presented in this article. Keywords: S phase, carburising, nitriding, colossal carbon supersaturation, &, kolsterising

This chapter gives an overview of the various precipitate phases that can form in the different classes of stainless steels. Besides the phases that are well-studied, a newly discovered phase, called the J phase, is also introduced. The conditions under which the different phases will form, the problems they cause, the methods for alleviating these problems, and the new methods for the detection of the various phases are presented.

This chapter focuses on precipitation-hardening stainless steels (PHSSs). The three main types of PHSSs, i.e., the semiaustenitic class, the martensitic class and the austenitic class, are described in detail. The duplex class is also briefly discussed. The different heat treatments, together with their effects on properties, that are commonly used for attaining precipitation strengthening in PHSSs are presented. Recent developments in the understanding of the precipitation sequences and the precipitates in PHSSs are introduced.

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

Carbon neutralization has drawn increasing attention for realizing the carbon cyclization and reducing the greenhouse effect. Although the C1 products, such as CO, can be achieved with a high Faraday efficiency, the targeted production of C2 fuels as well as the mechanism have not been systematically investigated. In this work, we carry out a first-principles study to screen dual-atom catalysts (DACs) for producing C2 fuels through the electrocatalytic carbon monoxide reduction reaction (e-CORR). We find that e-CORR on DAC-Co can produce methanol and ethylene, while e-CORR on DAC-Cu produces methanol, acetate, and ethylene. Importantly, the C2 products can be obtained more easily than the C1 products because of lower limiting potentials. Furthermore, we show that the explicit solvent can enhance the adsorption and influence the protonation steps, which subsequently affects the protonation and dimerization behavior as well as the performance and selectivity of e-CORR on DACs. Furthermore, we demonstrate that the C-C coupling is easy to be formed and stabilized if the Integrated Crystal Orbital Hamilton Population (ICOHP) is low because of the low energy barrier. Our findings provide not only guidance on the design of novel catalysts for e-CORR, but insightful understanding on the mechanism.

This thesis is on the phase transformation and magnetic behaviour of duplex stainless steels at different temperatures (from 350°C to 1300°C). Prior to thermal ageing, samples were differently pre-treated through plastic deformation and different solution treatments. The possibility of using duplex stainless steels for temperature measurement and temperature fluctuation monitoring has been explored. The microstructures of duplex stainless steels at different temperatures have been characterised by using optical metallography and electron microscopy. Below 550°C, the ferrite phase undergoes spinodal decomposition, which is followed by the precipitation of the G phase. Between 600 and 900 , the main transformation °C °C product is the intermetallic sigma phase. Between 900 and 1000 , the domina °C °C nt precipitate phase is carbide. While plastic deformation accelerates the kinetics of precipitation, raising the solution treatment temperature has the opposite effect. The attendant changes in the room-temperature and cryogenic magnetic properties of duplex stainless steels after different thermal ageing treatments have been studied by using a vibrating sample magnetometer and an a.c. magnetic susceptometer. Below 550°C when the ferrite decomposes spinodally, the room-temperature a.c. magnetic susceptibility might be used for temperature measurement. But between 600°C and 900°C when the sigma phase forms, the possibility of using duplex stainless steels for temperature measurement seems to be low. The cryogenic magnetic behaviour of the intermetallic sigma phase of the Fe-Cr-Ni-Mo system has been systematically studied. The feasibility of using room-temperature a.c. magnetic susceptibility for ferrite content measurement has been examined. The growth of the spinodal domain in the ferrite phase has been studied by using cryogenic a.c. magnetic susceptibility measurement. And the scaling law so obtained has been compared with those available in the literature. The feasibility of using cryogenic magnetic susceptibility for monitoring spinodal decomposition has been discussed. The transformation behaviour of the sigma phase has been investigated by using differential thermal analysis (DTA). The viability of using DTA and duplex stainless steels for temperature measurement has been explored.

Recent increase in popularity of indoor climbing allows possible applications of deep learning algorthms to classify and generate climbing routes. In this work, we employ a variational autoencoder to climbing routes in a standardized training apparatus MoonBoard, a well-known training tool within the climbing community. By sampling the encoded latent space, it is observed that the algorithm can generate high quality climbing routes. 22 generated problems are uploaded to the Moonboard app for user review. This algorithm could serve as a first step to facilitate indoor climbing route setting.

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapidity-dependent difference ($\Delta v_2$) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, $v_2$) between $\mathrm{D}^0$ ($\mathrm{\bar{u}c}$) and $\overline{\mathrm{D}}^0$ ($\mathrm{u\bar{c}}$) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of $\Delta v_2$. The rapidity-averaged value is found to be $\langle\Delta v_2 \rangle =$ 0.001 $\pm$ 0.001 (stat) $\pm$ 0.003 (syst) in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the $\mathrm{D}^0$ and $\overline{\mathrm{D}}^0$ mesons $v_2$ and triangular flow coefficient ($v_3$) as functions of rapidity, transverse momentum ($p_\mathrm{T}$), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt $\mathrm{D}^0$ meson $v_2$ values is observed, while the $v_3$ is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry.

The thesis describes a search for new physics in form of supersymmetry in hadronic final states and missing transverse energy (ET) using a dataset of 35.9 fb−1 collected during the 2016 proton-proton runs by the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The search uses robust kinematic variables to suppress backgrounds while maintaining good acceptance to a broad range of signal models and employs data-driven techniques to accurately determine backgrounds and systematic uncertainties. No evidence for Beyond Standard Model (BSM) physics is observed and simplified models are used to interpret the results. For gluino mediated models, the gluino mass up to 1850 GeV and the lightest symmetric particle (LSP) up to 1100 GeV are excluded. For light squark mediated models, the light squark mass up to 1350 GeV (700 GeV) and the LSP up to 650 GeV (400 GeV), assuming no degeneracy in the light squark masses (a degeneracy in light squark masses). For sbottom mediated models, the sbottom mass is excluded to 1075 GeV and the LSP mass up to 550 GeV. For stop mediated models, the stop mass is excluded up to 1075 GeV with the LSP mass up to 400 GeV.