High-Throughput Screening of Synergistic Transition Metal Dual-Atom Catalysts for Efficient Nitrogen Fixation

Rational design of bimetallic MBene for efficient electrocatalytic nitrogen reduction

Electrocatalytic nitrogen reduction reaction (NRR) is one of the most promising approaches to achieving green and efficient NH3 production. However, the designs of efficient NRR catalysts with high activity and selectivity still are severely hampered by inherent linear scaling relations among the adsorption energies of NRR intermediates. Herein, the properties of ten M3B4 type MBenes have been initially investigated for efficient N2 activation and reduction to NH3via first-principles calculations. We highlight that Cr3B4 MBene possesses remarkable NRR activity with a record-low limiting potential (-0.13 V). Then, this work proposes descriptor-based design principles that can effectively evaluate the catalytic activity of MBenes, which have been further employed to design bimetallic M2M'B4 MBenes. As a result, 5 promising candidates including Ti2YB4, V2YB4, V2MoB4, Nb2YB4, and Nb2CrB4 with excellent NRR performance have been extracted from 20 bimetallic MBenes. Further analysis illuminates that constructing bimetallic MBenes can selectively tune the adsorption strength of NHNH2** and NH2NH2**, and break the linear scaling relations between their adsorption energies, rendering them ideal for NRR. This work not only pioneers the application of MBenes as efficient NRR catalysts but also proposes rational design principles for boosting their catalytic performance.

Computational screening of pyrazine-based graphene-supported transition metals as single-atom catalysts for the nitrogen reduction reaction

Electrochemical synthesis of NH3 from N2 utilizing single-atom catalysts (SACs) is a promising strategy for industrial nitrogen fixation and chemical raw material production. In this work, single transition metals (TMs) anchored on pyrazine-based graphene (TM@py-GY) are systematically studied to screen potential electrocatalysts for the nitrogen reduction reaction (NRR) using first-principles calculations. Particularly, the descriptor φ related to electronegativity and valence electron number is selected to clarify the trend of NRR activity, realizing a fast-scan/estimation among various candidates. After a four-step screening process, WI@py-GY and MoII@py-GY SACs are screened with good structural stability, high selectivity, and high activity. Meanwhile, the thermodynamic stability of WI@py-GY and MoII@py-GY SACs is demonstrated to ensure their feasibility in real experimental conditions. Furthermore, electronic properties are also examined in detail to analyze activity origin. This work not only provides an effective and reliable method for screening electrochemical NRR catalysts with excellent performance but also provides guidance for the rational design of SACs.

Triggering Heteroatom Ensemble Effect over RuFe Alloy to Promote Nitrogen Chemisorption for Efficient Ammonia Electrosynthesis at Ambient Conditions

Ammonia (NH3) electrosynthesis from nitrogen (N2) provides a promising strategy for carbon neutrality, circumventing the energy-intensive and carbon-emitting Haber-Bosch process. However, the current system still presents unsatisfactory performance, and the bottleneck lies in the rational synthesis of catalytic centers with efficient N2 chemisorption ability. Herein, a heteroatom ensemble effect is deliberately triggered over RuFe alloy with spatial proximity of metal sites to promote electrocatalytic nitrogen reduction. The heteronuclear RuFe ensemble with increased surface polarization and modulated electronic structure offers the feasibility to optimize the adsorption configuration of electroactive substances and facilitate chemical bond scission. The promotion of N2 chemisorption and the following hydrogenation are demonstrated by the in situ Fourier transform infrared spectroscopy characterizations. The catalyst thus permits significantly enhanced conversion of N2 to NH3 in a 0.1 M HCl environment, with a maximum ammonia yield rate of 75.45 μg h-1 mg-1 and a high Faradaic efficiency of 35.49%.

Spin effect in dual-atom catalysts for electrocatalysis

The development of high-efficiency atomic-level catalysts for energy-conversion and -storage technologies is crucial to address energy shortages. The spin states of diatomic catalysts (DACs) are closely tied to their catalytic activity. Adjusting the spin states of DACs' active centers can directly modify the occupancy of d-orbitals, thereby influencing the bonding strength between metal sites and intermediates as well as the energy transfer during electro reactions. Herein, we discuss various techniques for characterizing the spin states of atomic catalysts and strategies for modulating their active center spin states. Next, we outline recent progress in the study of spin effects in DACs for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), electrocatalytic nitrogen/nitrate reduction reaction (eNRR/NO3RR), and electrocatalytic carbon dioxide reduction reaction (eCO2RR) and provide a detailed explanation of the catalytic mechanisms influenced by the spin regulation of DACs. Finally, we offer insights into the future research directions in this critical field.

Catalysts with Trimetallic Sites on Graphene-like C2N for Electrocatalytic Nitrogen Reduction Reaction: A Theoretical Investigation

Electrocatalytic nitrogen reduction reaction (NRR) is a green and highly efficient way to replace the industrial Haber-Bosch process. Herein, clusters consisting of three transition metal atoms loaded on C2N as NRR electrocatalysts are investigated using density functional theory (DFT). Meanwhile, Ca was introduced as a promoter and the role of Ca in NRR was investigated. It was found that Ca anchored to the catalyst can act as an electron donor and effectively promote the activation of N2 on M3. In both M3@C2N and M3Ca@C2N (M=Fe, Co, Ni), the limiting potential (UL) is less negative than that of the Ru(0001) surface and has the ability to suppress the competitive hydrogen evolution reaction (HER). Among them, Fe3@C2N is suggested to be the most promising candidate for NRR with high thermal stability, strong N2 adsorption ability, low limiting potential, and good NRR selectivity. The concepts of trimetallic sites and alkaline earth metal promoters in this work provide theoretical guidance for the rational design of atomically active sites in electrocatalytic NRR.

Engineered Electron-Deficient Sites at Boron-Doped Strontium Titanate/Electrolyte Interfaces Accelerate the Electrocatalytic Reduction of N2 to NH3: A Combined DFT and Experimental Electrocatalysis Study

The development of an efficient, selective, and durable catalysis system for the electrocatalytic N2 reduction reaction (ENRR) is a promising strategy for the sustainable production of ammonia. The high-performance ENRR is limited by two major challenges: poor adsorption of N2 over the catalyst surface and abysmal N2 solubility in aqueous electrolytes. Herein, with the help of our combined density functional theory (DFT) calculations and experimental electrocatalysis study, we demonstrate that concurrently induced electron-deficient Lewis acid sites in an electrocatalyst and in an electrolyte medium can significantly boost the ENRR performance. The DFT calculations, ex situ X-ray photoelectron and FTIR spectroscopy, electrochemical measurements, and N2-TPD (temperature-programmed desorption) over boron-doped strontium titanate (BSTO) samples reveal that the Lewis acid-base interactions of N2 synergistically enhance the adsorption and activation of N2. Besides, the B-dopant induces the defect sites (oxygen vacancies and Ti3+) that assist in enhanced N2 adsorption and results in suppressed hydrogen evolution due to B-induced electron-deficient sites for H+ adsorption. The insights from the DFT study evince that B prefers the Srtop position (on top of Sr) where N2 adsorbs in an end-on configuration, which favors the associative alternating pathway and suppresses the competitive hydrogen evolution. Thus, our combined experimental and DFT study demonstrates an insight toward enhancing the ENRR performance along with the suppressed hydrogen evolution via concurrently engineered electron-deficient sites at electrode and electrolyte interfaces.

Density Functional Theory Investigation on the Nitrogen Reduction Mechanism in Two-Dimensional Transition-Metal Boride with Ordered Metal Vacancies

The creation of ordered collective vacancies in experiment proves challenging within a two-dimensional lattice, resulting in a limited understanding of their impact on catalyst performance. Motivated by the successful experimental synthesis of monolayer molybdenum borides with precisely ordered metal vacancies [Zhou et al. Science 2021, 373, 801-805] through dealloying, the nitrogen reduction reaction (NRR) in monolayer borides was systematically investigated to elucidate the influence of such ordered metal vacancies on catalytic reactions and the underlying mechanisms. The results reveal that the N-containing intermediates tend to dissociate, facilitating the NRR process with reduced UL. The emergence of ordered metal vacancies modulates the electronic properties of the catalyst and partially facilitates the decomposition of N-containing intermediates. However, the UL for NRR in Mo4/3B2 and W4/3B2 exhibits a significant increase. The compromised electrochemical performance is explained through the development of a simple electronic descriptor of the d-p band center (ΔdM-pB). Among these materials, Mo4/3Sc2/3B2 exhibits the most superior catalytic activity with a UL of -0.5 V and favorable NRR selectivity over the HER. Our results provide mechanistic insights into the role of ordered metal vacancies in transition-metal boride for the NRR and highlight a novel avenue toward the rational design of superior NRR catalysts.

Advancing electrocatalytic reactions through mapping key intermediates to active sites via descriptors

Descriptors play a crucial role in electrocatalysis as they can provide valuable insights into the electrochemical performance of energy conversion and storage processes. They allow for the understanding of different catalytic activities and enable the prediction of better catalysts without relying on the time-consuming trial-and-error approaches. Hence, this comprehensive review focuses on highlighting the significant advancements in commonly used descriptors for critical electrocatalytic reactions. First, the fundamental reaction processes and key intermediates involved in several electrocatalytic reactions are summarized. Subsequently, three types of descriptors are classified and introduced based on different reactions and catalysts. These include d-band center descriptors, readily accessible intrinsic property descriptors, and spin-related descriptors, all of which contribute to a profound understanding of catalytic behavior. Furthermore, multi-type descriptors that collectively determine the catalytic performance are also summarized. Finally, we discuss the future of descriptors, envisioning their potential to integrate multiple factors, broaden application scopes, and synergize with artificial intelligence for more efficient catalyst design and discovery.

Advanced dual-atom catalysts on graphitic carbon nitride for enhanced hydrogen evolution via water splitting

In this comprehensive investigation, we explore the effectiveness of 55 dual-atom catalysts (DACs) supported on graphitic carbon nitride (gCN) for both alkaline and acidic hydrogen evolution reactions (HER). Employing density functional theory (DFT), we scrutinize the thermodynamic and kinetic profiles of these DACs, revealing their considerable potential across a diverse pH spectrum. For acidic HER, our results identify catalysts such as FePd-gCN, CrCr-gCN, and NiPd-gCN, displaying promising ΔGH* values of 0.0, 0.0, and -0.15 eV, respectively. This highlights their potential effectiveness in acidic environments, thereby expanding the scope of their applicability. Within the domain of alkaline HER, this study delves into the thermodynamic and kinetic profiles of DACs supported on gCN, utilizing DFT to illuminate their efficacy in alkaline HER. Through systematic evaluation, we identify that DACs such as CrCo-gCN, FeRu-gCN, and FeIr-gCN not only demonstrate favorable Gibbs free energy change (ΔGmax) for the overall water splitting reaction of 0.02, 0.27, and 0.38 eV, respectively, but also feature low activation energies (Ea) for water dissociation, with CrCo-gCN, FeRu-gCN, and FeIr-gCN notably exhibiting the Ea of just 0.42, 0.33, and 0.42 eV, respectively. The introduction of an electronic descriptor (φ), derived from d electron count (Nd) and electronegativity (ETM), provides a quantifiable relationship with catalytic activity, where a lower φ corresponds to enhanced reaction kinetics. Specifically, φ values between 4.0-4.6 correlate with the lowest kinetic barriers, signifying a streamlined HER process. Our findings suggest that DACs with optimized φ values present a robust approach for the development of high-performance alkaline HER electrocatalysts, offering a pathway towards the rational design of energy-efficient catalytic systems.

Unraveling the activity trends of T-C2N based Single-Atom catalysts for electrocatalytic nitrate reduction via high-throughput screening

Electrochemical nitrate reduction reaction (NO3RR) offers a cost-effective and environmentally friendly method to simultaneously yield valuable NH3and alleviate NO3-pollution under mild operating conditions.However, this complicated eight-electron reaction suffers from low selectivity and Faradaic efficiency, which highlight the importance of developing efficient catalysts, but still a critical challenge. Here, a theoretical screening is performed on transition metal-tetragonal carbon nitride (TM@T-C2N) as active and selective electrocatalysts for NO3RR, where detailed reaction mechanisms and activity origins are explored. In addition, five-step screening criteria and volcano plots enable fast prescreening among numerous candidates.We identify that V@T-C2N and Cr@T-C2N are promising candidates with low overpotentials and high selectivity and stability. In particular, a significant negative correlation between the adsorption strength ofnitrate and the Gibbs free energy for the last proton-electron coupling step (*NH2→*NH3) was existed, which is considerably advantaged to track the activity trend and reveal the origin of activity. This work provides theoretical insights into the rational design of TM-N4/C catalysts for NO3RR andpaves a valuable electrochemical screening framework for other multi-step reactions.

Design of Single-Atom Catalysts on C5N2 for Nitrogen Fixation at Ambient Conditions: A First-Principles Study

Single atom catalysts (SACs) exhibit the flexible coordination structure of the active site and high utilization of active atoms, making them promising candidates for nitrogen reduction reaction (NRR) under ambient conditions. By the aid of first-principles calculations based on DFT, we have systematically explored the NRR catalytic behavior of thirteen 4d- and 5d-transition metal atoms anchored on 2D porous graphite carbon nitride C5 ${_5 }$ N2 ${_2 }$ . With high selectivity and outstanding activity, Zr, Nb, Mo, Ta, W and Re-doped C5 ${_5 }$ N2 ${_2 }$ are identified as potential nominees for NRR. Particularly, Mo@C5 ${_5 }$ N2 ${_2 }$ possesses an impressive low limiting potential of -0.39 V (corresponding to a very low temperature and atmospheric pressure), featuring the potential determining step involving *N-N transitions to *N-NH via the distal path. The catalytic performance of TM@C5 ${_5 }$ N2 ${_2 }$ can be well characterized by the adsorption strength of intermediate *N2 ${_2 }$ H. Moreover, there exists a volcanic relationship between the catalytic property UL ${_{\rm{L}} }$ and the structure descriptor Ψ ${{{\Psi }}}$ , which validates the robustness and universality of Ψ ${{{\Psi }}}$ , combined with our previous study. This work sheds light on the design of SACs with eminent NRR performance.

Reducing Overpotential of Lithium-Oxygen Batteries by Diatomic Metal Catalyst Orbital Matching Strategy

Aprotic Li-O2 batteries have sparked attention in recent years due to their ultrahigh theoretical energy density. Nevertheless, their practical implementation is impeded by the sluggish reaction kinetics at the cathode. Comprehending the catalytic mechanisms is pivotal to developing efficient cathode catalysts for high-performance Li-O2 batteries. Herein, the intrinsic activity map of Li-O2 batteries is established based on the specific adsorption mode of O2 induced by diatomic catalyst orbital matching and the transfer-acceptance-backdonation mechanism, and the four-step screening strategy based on the intrinsic activity map is proposed. Guided by the strategy, FeNi@NC and FeCu@NC promising durable stability with a low overpotential are screened out from 27 Fe-Metal diatomic catalysts. Our research not only provides insights into the fundamental understanding of the reaction mechanism of Li-O2 batteries but also accelerates the rational design of efficient Li-O2 batteries based on the structure-activity relationship.

Impact of Vacancy Defects on Electrochemical Nitrogen Reduction Reaction Performance of MXenes

We investigated electrochemical nitrogen reduction reaction (eNRR) on MXenes consisting of the vacancy defects in the functional layer using density functional theory calculations. We considered Mo2C, W2C, Mo2N, and W2N MXenes with F, N, and O functionalization and investigated distal and alternative associative pathways. We analyzed these MXenes for eNRR based on N2 adsorption energy, NH3 desorption energy, NRR selectivity, and electrochemical limiting potential. While we find that most of the considered MXenes surfaces are more favorable for eNRR compared to hydrogen evolution, these surfaces also have strong NH3 binding (>-1.0 eV) and thus will be covered with NH3 during operating conditions. Amongst all considered MXenes, only W2NF2 is found to have a low NH3 desorption energy along with low eNRR overpotential and selectivity towards eNRR. The obtained eNRR overpotential and NH3 desorption energy on W2NF2 are superior to those reported for pristine W2N3 as well as functionalized MXenes.

Machine Learning-Accelerated High-Throughput Computational Screening: Unveiling Bimetallic Nanoparticles with Peroxidase-Like Activity

Bimetallic nanoparticles (NPs) with peroxidase-like (POD-like) activity play a crucial role in biosensing, disease treatment, environmental management, and other fields. However, their development is impeded by a vast range of tunable properties in components and structures, making the establishment of structure-effect relationships and the discovery of active materials challenging. Addressing this, we established robust scaling relationships by meticulously analyzing the catalytic reaction networks of pure metal NPs, which laid the volcano-shaped correlation between the activity and O* adsorption energy. Utilizing these relationships, we introduced an innovative and versatile descriptor of the NPs, which was then integrated into a machine learning-accelerated high-throughput computational workflow, significantly boosting the predictive accuracy for the POD-like activity of bimetallic NPs. Our methodological approach enabled the successful prediction of activities for 1260 bimetallic NPs, leading to the identification of several highly effective catalysts. Furthermore, we distilled several strategies for designing efficient bimetallic NPs based on our screening results.

Hot Carrier Controlled Nitrogen Fixation Reaction in Metal-Free Boron-Anchored Aza-COF: Insight from Nonadiabatic Molecular Dynamics Simulation

Designing highly efficient photocatalysts for the production of renewable energy is a challenging task that necessitates simultaneous control of chemical activity and photocarrier dynamics for a particular reaction. To this end, we have investigated the catalytic mechanism and real-time photocarrier dynamics of the nitrogen reduction reaction (NRR) at the metal-free boron-functionalized 2D aza-COF (B-aza-COF), an inexpensive and environmentally friendly semiconductor. By employing density functional theory (DFT) and time-dependent ab initio nonadiabatic molecular dynamics simulation, we have investigated the electronic structure, light harvesting ability, free energy change, and dynamics of photoexcited carriers. Our calculated results reveal that the gas phase N2 molecule can be effectively reduced into NH3 on B-aza-COF under UV-visible light. Therefore, our investigation on the design of efficient photocatalysts for the nitrogen reduction reaction (NRR) provides a cost-effective opportunity for the sustainable production of NH3.

Research progress of dual-atom site catalysts for photocatalysis

Dual-atom site catalysts (DASCs) have sparked considerable interest in heterogeneous photocatalysis as they possess the advantages of excellent photoelectronic activity, photostability, and high carrier separation efficiency and mobility. The DASCs involved in these important photocatalytic processes, especially in the photocatalytic hydrogen evolution reaction (HER), CO2 reduction reaction (CO2RR), N2/nitrate reduction, etc., have been extensively investigated in the past few years. In this review, we highlight the recent progress in DASCs that provides fundamental insights into the photocatalytic conversion of small molecules. The controllable preparation and characterization methods of various DASCs are discussed. Subsequently, the reaction mechanisms of the formation of several important molecules (hydrogen, hydrocarbons and ammonia) on DASCs are introduced in detail, in order to probe the relationship between DASCs's structure and photocatalytic activity. Finally, some challenges and outlooks of DASCs in the photocatalytic conversion of small molecules are summarized and prospected. We hope that this review can provide guidance for in-depth understanding and aid in the design of efficient DASCs for photocatalysis.

Proposals for gas-detection improvement of the FeMPc monolayer towards ethylene and formaldehyde by using bimetallic synergy

Development and fabrication of a novel gas sensor with superb performance are crucial for enabling real-time monitoring of ethylene (C2H4) and formaldehyde (H2CO) emissions from industrial manufacture. Herein, first-principles calculations and AIMD simulations were carried out to investigate the effect of the Fe-M dimer on the adsorption of C2H4 and H2CO on metal dimer phthalocyanine (FeMPc, M = Ti-Zn) monolayers, and the electronic structures and sensing properties of the above adsorption systems were systematically discussed. The results show that the FeMPc (M = Ti, V, Cr, Mn) monolayers interact with C2H4 and H2CO by chemisorption except for the FeMnPc/H2CO system, while the other adsorption systems are all characterized by physisorption. Interestingly, the adsorption strength of C2H4 and H2CO can be effectively regulated by the bimetallic synergy of the Fe-M dimer. Moreover, the FeCrPc and FeMnPc monolayers exhibit excellent sensitivity towards C2H4 and H2CO, and have short recovery time (4.69 ms-2.31 s) for these gases at room temperature due to the effective surface diffusion at 300 K. Consequently, the FeCrPc and FeMnPc materials can be utilized as high-performance, reusable gas sensors for detecting C2H4 and H2CO, and have promising applications in monitoring the release of ethylene and formaldehyde from industrial processes.

NiFeB-assisted adsorption and activation of nitrogen to improve the photooxidation activity of zinc porphyrin

This study effectively addresses the challenge of nitrogen adsorption and activation in photocatalytic nitrogen fixation by introducing an oxidizing co-catalyst, NiFeB hydroxides. The NiFeB hydroxides could provide reactive active sites and significantly enhance the nitrogen oxidation activity, offering a novel pathway for co-catalysts in nitrogen fixation reactions.

Design of MoS2 edge-anchored single-atom catalysts for propane dehydrogenation driven by DFT and microkinetic modeling

The design of efficient catalysts for direct propane dehydrogenation (PDH) to inhibit coke formation and deactivation of traditional Pt-based catalysts are challenging tasks. Herein, by exploiting the unique geometric feature and tunability of single atom catalysts (SACs), a wide range of 3d-5d transition metals anchored on the MoS2 edge in the single atom form (TM1-S4/edge) are comprehensively investigated for the PDH application by first-principles calculations, ab initio molecular dynamics (AIMD) simulations and microkinetic modeling. Five criteria are assessed in terms of the feasibility of preparation, practical stability, feasibility of recovery after air oxidation, activity and selectivity. We identified Ru1-S4/edge SAC as the most promising candidate with activity six times higher than that of the conventional Pt(111) catalyst. Interestingly, AIMD simulations show that the motif region of the highly reactive TM1-S4/edge SACs (such as Ru, Os, Rh, and Ir) exhibits a dynamic change, with a TM-coordinated S atom tending to flutter at reaction temperatures and return to its initial position when the species is adsorbed on TMs, thereby affecting the PDH activities. In addition to identifying the potential PDH catalyst from a practical application point of view, we believe that this study also provides a comprehensive picture for the theoretical screening of low-coordination single-atom catalysts.

A Self-Consistent Framework for Tailored Single-Atom Catalysts in Electrocatalytic Nitrogen Reduction

The catalytic activity of single-atom catalysts (SACs) is crucially affected by the actual ligand configurations under the reaction condition; thus, carefully considering the reaction condition is crucial for the theoretical design of SACs. With single metal atoms supported by g-C3N4 as a model system, a self-consistent screening framework is proposed for the theoretical design of SACs with respect to the nitrogen reduction reaction (NRR). Pourbaix diagrams are constructed on the basis of various co-adsorption configurations of N2, H, and OH. Possible stable configurations containing N2 under the expected reaction condition are considered to obtain the limiting potential of NRR, and the stability of the configuration at the calculated UL is rechecked. With this framework, AC stacking of double-layer g-C3N4-supported Nb and AA stacking and AB stacking of double-layer g-C3N4-supported W are predicted to exhibit superior NRR activity with UL values of -0.36, -0.45, and -0.52 V, respectively. This procedure can be widely applied to the screening of SACs for electrocatalytic reactions.

Structural Design of π-d Conjugated TMx B3 N3 S6 (x=2, 3) Monolayer Toward Electrocatalytic Ammonia Synthesis

Single-atom catalysts (SACs) have attracted wide attention to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3-, 4-coordinated and π-d conjugated TMx B3 N3 S6 (x=2, 3, TM=Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I-TM2 B3 N3 S6 and III-TM3 B3 N3 S6 are the reasonable 3-coordinated and 4-coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3-coordinated I-TM2 B3 N3 S6 and 4-coordinated III-TM3 B3 N3 S6 monolayers with different single transition metal atoms were systematically investigated. The results reveal that B3 N3 S6 ligand is an ideal support for TM atoms due to existence of strong TM-S bonds. The 3-coordinated I-V2 B3 N3 S6 is the best SAC with the low limiting potential (UL ) of -0.01 V, excellent stability (Ef =-0.32 eV, Udiss =0.02 V) and remarkable selectivity characteristics. This work not only provides novel π-d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis.

Review of Carbon Support Coordination Environments for Single Metal Atom Electrocatalysts (SACS)

This topical review focuses on the distinct role of carbon support coordination environment of single-atom catalysts (SACs) for electrocatalysis. The article begins with an overview of atomic coordination configurations in SACs, including a discussion of the advanced characterization techniques and simulation used for understanding the active sites. A summary of key electrocatalysis applications is then provided. These processes are oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), and carbon dioxide reduction reaction (CO2 RR). The review then shifts to modulation of the metal atom-carbon coordination environments, focusing on nitrogen and other non-metal coordination through modulation at the first coordination shell and modulation in the second and higher coordination shells. Representative case studies are provided, starting with the classic four-nitrogen-coordinated single metal atom (MN4 ) based SACs. Bimetallic coordination models including homo-paired and hetero-paired active sites are also discussed, being categorized as emerging approaches. The theme of the discussions is the correlation between synthesis methods for selective doping, the carbon structure-electron configuration changes associated with the doping, the analytical techniques used to ascertain these changes, and the resultant electrocatalysis performance. Critical unanswered questions as well as promising underexplored research directions are identified.

High-Throughput Screening of Effective Dual Atom Catalysts for the Nitric Oxide Reduction Reaction

Electrochemical NO-to-NH3 conversion has been attracting more attention in the field of green energy, which, however, imposes restrictions on the catalysts. We therefore design a family of dual atom catalysts (DACs) TM1TM2@g-CN and perform high-throughput screening to position the effective catalysts for electrocatalytic NO-to-NH3 conversion from first-principles computations. We identify that TiCr@g-CN (-0.37 V), TiMo@g-CN (-0.36 V), and MnMo@g-CN (-0.43 V) are promising candidates with low overpotentials. In particular, we find that MoMo@g-CN can spontaneously reduce NO to NH3, which makes it an excellent electrocatalyst for the NO reduction reaction (NORR) to be translated to experiments. In terms of the local geometry feature and local electronic structures, we unravel the origin of the high NORR activity and high selectivity of the DAC MoMo@g-CN.

Controllable Electrocatalytic to Photocatalytic Conversion in Ferroelectric Heterostructures

Photocatalytic and electrocatalytic reactions to produce value-added chemicals offer promising solutions for addressing the energy crisis and environmental pollution. Photocatalysis is driven by light excitation and charge separation and relies on semiconducting catalysts, while electrocatalysis is driven by external electric current and is mostly based on metallic catalysts with high electrical conductivity. Due to the distinct reaction mechanism, the conversion between the two catalytic types has remained largely unexplored. Herein, by means of density functional theory (DFT) simulations, we demonstrated that the ferroelectric heterostructures Mo-BN@In2Se3 and WSe2@In2Se3 can exhibit semiconducting or metallic features depending on the polarization direction as a result of the built-in field and electron transfer. Using the nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) as examples, the metallic heterostructures act as excellent electrocatalysts for these reactions, while the semiconducting heterostructures serve as the corresponding photocatalysts with improved optical absorption, enhanced charge separation, and low Gibbs free energy change. The findings not only bridge physical phenomena of the electronic phase transition with chemical reactions but also offer a new and feasible approach to significantly improve the catalytic efficiency.

Multifunctional carbon nitride nanoarchitectures for catalysis

Catalysis is at the heart of modern-day chemical and pharmaceutical industries, and there is an urgent demand to develop metal-free, high surface area, and efficient catalysts in a scalable, reproducible and economic manner. Amongst the ever-expanding two-dimensional materials family, carbon nitride (CN) has emerged as the most researched material for catalytic applications due to its unique molecular structure with tunable visible range band gap, surface defects, basic sites, and nitrogen functionalities. These properties also endow it with anchoring capability with a large number of catalytically active sites and provide opportunities for doping, hybridization, sensitization, etc. To make considerable progress in the use of CN as a highly effective catalyst for various applications, it is critical to have an in-depth understanding of its synthesis, structure and surface sites. The present review provides an overview of the recent advances in synthetic approaches of CN, its physicochemical properties, and band gap engineering, with a focus on its exclusive usage in a variety of catalytic reactions, including hydrogen evolution reactions, overall water splitting, water oxidation, CO2 reduction, nitrogen reduction reactions, pollutant degradation, and organocatalysis. While the structural design and band gap engineering of catalysts are elaborated, the surface chemistry is dealt with in detail to demonstrate efficient catalytic performances. Burning challenges in catalytic design and future outlook are elucidated.

Building up a view and understanding of the multifunctional activity of black phosphorous nanosheet modified with the metal atom

Constructing metal-semiconductor interfaces by loading metal atoms onto two-dimensional material to build atomically dispersed single-atom catalysts (SACs) has emerged as a new frontier for improving atom utilization and designing multifunctional electrocatalysts. Nowadays, studies on black phosphorus nanosheets in electrocatalysis have received much attention and the successful preparation of metal nanoparticle/black phosphorus (BP) hybrid electrocatalysts indicates BP nanosheets can serve as a potential support platform for SACs. Herein, by using large-scale ab initio calculations, we explored a large composition space of SACs with transition metal atoms supported on BP monolayer (M-BP) and built a comprehensive picture of activity trend, stability, and electronic origin towards oxygen reduction and evolution reaction (ORR and OER) and hydrogen evolution reaction (HER). The results show that the catalytic activity can be widely tuned by reasonable regulation of metal atoms. Ni-, Pd-, and Pt-BP could effectively balance the binding strength of the target intermediates, thus achieving efficient bifunctional activity for OER and ORR. Favorable bifunctional catalytic performance for OER and HER can be realized on Rh-BP. Especially, Pt-BP exhibits promising trifunctional activity towards OER, ORR, and HER. Multiple-level corrections among overpotential, Gibbs free energy, orbital population, and d-band center reveal that the trend and origin of catalytic activity are intrinsically determined by the d-band center of metal sites. The thermodynamic and dynamic stability simulations demonstrate that the active metal centers are firmly anchored on BP substrate with intact M-P bonds. These findings provide a theoretical basis for the rational design of BP-based SACs toward promising multifunctional activity.

Tailoring the coordination environment of double-atom catalysts to boost electrocatalytic nitrogen reduction: a first-principles study

Tailoring the coordination environment is an effective strategy to modulate the electronic structure and catalytic activity of atomically dispersed transition-metal (TM) catalysts, which has been widely investigated for single-atom catalysts but received less attention for emerging double-atom catalysts (DACs). Herein, based on first-principles calculations, taking the commonly studied N-coordinated graphene-based DACs as references, we explored the effect of coordination engineering on the catalytic behaviors of DACs towards the electrocatalytic nitrogen reduction reaction (NRR), which is realized through replacing one N atom by the B or O atom to form B, N or O, N co-coordinated DACs. We found that B, N or O, N co-coordination could significantly strengthen N2 adsorption and alter the N2 adsorption pattern of the TM dimer active center, which greatly facilitates N2 activation. Moreover, on the studied DACs, the linear scaling relationship between the binding strengths of key intermediates can be attenuated. Consequently, the O, N co-coordinated Mn2 DACs, exhibiting an ultralow limiting potential of -0.27 V, climb to the peak of the activity volcano. In addition, the experimental feasibility of this DAC system was also identified. Overall, benefiting from the coordination engineering effect, the chemical activity and catalytic performance of the DACs for NRR can be significantly boosted. This phenomena can be understood from the adjusted electronic structure of the TM dimer active center due to the changes of its coordination microenvironment, which significantly affects the binding strength (pattern) of key intermediates and changes the reaction pathways, leading to enhanced NRR activity and selectivity. This work highlights the importance of coordination engineering in developing DACs for the electrocatalytic NRR and other important reactions.

Dual Atom Catalysts for Energy and Environmental Applications

The pursuit of high metal utilization in heterogeneous catalysis has triggered the burgeoning interest of various atomically dispersed catalysts. Our aim in this review is to assess key recent findings in the synthesis, characterization, structure-property relationship and computational studies of dual-atom catalysts (DACs), which cover the full spectrum of applications in thermocatalysis, electrocatalysis and photocatalysis. In particular, combination of qualitative and quantitative characterization with cooperation with DFT insights, synergies and superiorities of DACs compare to counterparts, high-throughput catalyst exploration and screening with machine-learning algorithms are highlighted. Undoubtably, it would be wise to expect more fascinating developments in the field of DACs as tunable catalysts.

d- and p-Block single-atom catalysts supported by BN nanocages toward electrochemical reactions of N2 and O2

Electrocatalysis is involved in many energy storage and conversion devices, triggering research and development of electrocatalysts, particularly single-atom catalysts (SACs). The introduction of the strain effect to enhance the performance of SACs has drawn ever-increasing research attention, which can tailor the local atomic and electronic structure of active sites. Herein, via high throughput calculations, we have explored the effects of strain on the catalytic performance of SACs with MN4 configuration for electrochemical reactions of N2 and O2 by incorporating d- and p-block single metal atoms into BN nanocages (BNNCs). The calculations demonstrate that Os@BNNC exhibits the highest catalytic activity for the nitrogen reduction reaction (NRR) with a limiting potential of -0.29 V. Co@BNNC can serve as an excellent bifunctional SAC for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), with overpotentials of 0.32 and 0.37 V, respectively. In particular, Sn@BNNC with a p-block metal as the active center is a competitive SAC for the ORR with an overpotential of 0.64 V. More interestingly, the NRR and ORR performances of SACs supported by BNNCs have a close correlation with the structural and electronic properties of adsorbed N2 and O2 molecules, which proves that controlling the adsorption energy of N2 and O2 molecules is crucial to improving the catalytic activity of BNNC. The current investigation opens up an avenue for designing SACs embedded in nanocages possessing intrinsically curved surfaces for electrochemical reactions.

Active Learning the High-Dimensional Transferable Hubbard U and V Parameters in the DFT + U + V Scheme

Density functional theory (DFT) is a powerful quantum mechanical computational tool to perform electronic structure calculations for materials. Few DFT methods can ensure accuracy and efficiency simultaneously. DFT + U + V is an alternative effective approach to overcome this drawback. However, the accuracy sensitively depends on the self-consistent estimation of the high-dimensional onsite and intersite Hubbard interaction U and V terms. We propose Bayesian optimization using a dropout (BOD) algorithm, one type of active learning method, to optimize U and V terms. The DFT + U + V with U/V obtained by BOD can produce improved electronic properties for diverse bulk materials of comparable quality to the hybrid functionals with lower computational cost compared to the linear response approach. Note that the band gaps calculated by BOD are somewhat different from that of hybrid functionals by simply applying the same U/V parameters as in the case of surface slabs and interfaces, which suggests that the transferability of U/V from the bulk models to slabs and interfaces is not as well as expected. BOD is extended to calculate the U/V parameters for slabs and interfaces and reach similar results as bulk solids. Moreover, we find that the U/V are reasonably transferable between surface slabs and interfaces with different thicknesses under various effects of quantum confinement, which contributes to fast access to the electronic properties of large-scale systems with higher accuracy.

Single B-vacancy enriched α1-borophene sheet: an efficient metal-free electrocatalyst for CO2 reduction

By employing first principles calculations, we have studied the electronic structures of pristine (α1) and different defective (α1-t1, α1-t2) borophene sheets to understand the efficacy of such systems as metal-free electrocatalysts for the CO2 reduction reaction. Among the three studied systems, only α1-t1, the defective borophene sheet created by removal of a 5-coordinated boron atom, can chemisorb and activate a CO2 molecule for its subsequent reduction processes, leading to different C1 chemicals, followed by selective conversion into C2 products by multiple proton coupled electron transfer steps. The computed onset potentials for the C1 chemicals such as CH3OH and CH4 are low enough. On the other hand, in the case of the C2 reduction process, the C-C coupling barrier is only 0.80 eV in the solvent phase which produces CH3CHO and CH3CH2OH with very low onset potential values of -0.21 and -0.24 V, respectively, suppressing the competing hydrogen evolution reaction.

Synergy of dual-atom catalysts deviated from the scaling relationship for oxygen evolution reaction

Dual-atom catalysts, particularly those with heteronuclear active sites, have the potential to outperform the well-established single-atom catalysts for oxygen evolution reaction, but the underlying mechanistic understanding is still lacking. Herein, a large-scale density functional theory is employed to explore the feasibility of *O-*O coupling mechanism, which can circumvent the scaling relationship with improving the catalytic performance of N-doped graphene supported Fe-, Co-, Ni-, and Cu-containing heteronuclear dual-atom catalysts, namely, M'M@NC. Based on the constructed activity maps, a rationally designed descriptor can be obtained to predict homonuclear catalysts. Seven heteronuclear and four homonuclear dual-atom catalysts possess high activities that outperform the minimum theoretical overpotential. The chemical and structural origin in favor of *O-*O coupling mechanism thus leading to enhanced reaction activity have been revealed. This work not only provides additional insights into the fundamental understanding of reaction mechanisms, but also offers a guideline for the accelerated discovery of efficient catalysts.

Activating dual atomic electrocatalysts for the nitric oxide reduction reaction through the P/S element

The development of efficient atomic electrocatalysts to resolve the activity and selectivity issues of the nitric oxide reduction reaction (NORR) has increasingly received more attention but is still challenging. The current research on the dual atomic NORR electrocatalyst is exclusively focused on TM atoms. Herein, we propose a novel mechanism of introducing a P/S element, which takes advantage of finite orbitals to active the transition metal (TM) atoms of dual atomic electrocatalysts for NORR. The finite orbitals can hinder the capture of the lone pair electrons of NO but modulate the electronic configurations of the neighboring TM and thus the "donation-backdonation" mechanism can be realized. Through large-scale first-principles calculations, the catalytic performance of a series of P/S-TM biatoms supported by the monolayer CN (P/S-TM@CN) is evaluated. According to a "four-step" screening strategy, P-Cu@CN and S-Ni@CN are successfully screened as promising catalysts with outstanding activity and high selectivity for direct NO-to-NH₃ conversion. Moreover, we identify Δε_d-p as a valid descriptor to evaluate the adsorption of NO on such catalysts, allowing for reducing the number of catalytic candidates. Our work thus provides a new direction for the rational design of dual atomic electrocatalysts.

A High-Throughput Screening toward Efficient Nitrogen Fixation: Transition Metal Single-Atom Catalysts Anchored on an Emerging π-π Conjugated Graphitic Carbon Nitride (g-C10N3) Substrate with Dirac Dispersion

TM-N_x is becoming a comforting catalytic center for sustainable and green ammonia synthesis under ambient conditions, resulting in increasing interest in single-atom catalysts (SACs) for the electrochemical nitrogen reduction reaction (NRR). However, given the poor activity and unsatisfactory selectivity of existing catalysts, it remains a long-standing challenge to design efficient catalysts for nitrogen fixation. Currently, the two-dimensional (2D) graphitic carbon-nitride substrate provides abundant and evenly distributed holes for stably supporting transition-metal atoms, which presents a fascinating prospect for overcoming this challenge and promoting single-atom NRR. An emerging holey graphitic carbon-nitride skeleton with a C₁₀N₃ stoichiometric ratio (g-C₁₀N₃) from a supercell of graphene is constructed, which provides outstanding electric conductivity for achieving high-efficiency NRR due to the Dirac band dispersion. Herein, a high-throughput first-principles calculation is carried out to evaluate the feasibility of π-d conjugated SACs resulting from a single TM atom anchored on g-C₁₀N₃ (TM = Sc-Au) for NRR. We find that W metal embedded in g-C₁₀N₃ (W@g-C₁₀N₃) can compromise the ability to adsorb the key target reaction species (N₂H and NH₂), hence acquiring an optimal NRR behavior among 27 TM-candidates. Our calculations demonstrate that W@g-C₁₀N₃ shows a well-suppressed HER ability and, impressively, a low energy cost of -0.46 V. Additionally, all-around descriptors are proposed to uncover the fundamental mechanism of NRR activity, among which a 3D volcano plot (limiting potential, screening strategy, and electron origin) uncovers the NRR activity trend, achieving a quick and high-efficiency prescreening for numerous candidates. Overall, the strategy of the structure- and activity-based TM-N_x-containing unit design will offer useful insight for further theoretical and experimental attempts.

Interlayer Charge Transfer Regulates Single-Atom Catalytic Activity on Electride/Graphene 2D Heterojunctions

Single-atom catalysts with structure and activity tunability have attracted significant attention for energy and environmental applications. Herein we present a first-principles study of single-atom catalysis on two-dimensional graphene and electride heterostructures. The anion electron gas in the electride layer enables a colossal electron transfer to the graphene layer, with the degree of transfer being controllable by the selection of electride. The charge transfer tunes the d-orbital electron occupancy of a single metal atom, enhancing the catalytic activity of hydrogen evolution reactions and oxygen reduction reactions. The strong correlation between the adsorption energy E_ads and the charge variation Δq suggests that interfacial charge transfer is a critical catalytic descriptor for the heterostructure-based catalysts. The polynomial regression model proves the importance of charge transfer and accurately predicts the adsorption energy of ions and molecules. This study provides a strategy to obtain high-efficiency single-atom catalysts using two-dimensional heterostructures.

Near ambient N2 fixation on solid electrodes versus enzymes and homogeneous catalysts

The Mo/Fe nitrogenase enzyme is unique in its ability to efficiently reduce dinitrogen to ammonia at atmospheric pressures and room temperature. Should an artificial electrolytic device achieve the same feat, it would revolutionize fertilizer production and even provide an energy-dense, truly carbon-free fuel. This Review provides a coherent comparison of recent progress made in dinitrogen fixation on solid electrodes, homogeneous catalysts and nitrogenases. Specific emphasis is placed on systems for which there is unequivocal evidence that dinitrogen reduction has taken place. By establishing the cross-cutting themes and synergies between these systems, we identify viable avenues for future research.

Theoretical exploration of the nitrogen fixation mechanism of two-dimensional dual-metal TM1TM2@C9N4 electrocatalysts

The electrochemical nitrogen reduction reaction (eNRR) to NH₃ has become an alternative to traditional NH₃ production techniques, while developing NRR catalysts with high activity and high selectivity is of great importance. In this study, we systematically investigated the potentiality of dual transition metal (TM) atom anchored electrocatalysts, TM₁TM₂@C₉N₄ (TM₁, TM₂ = 3(4)d TM atoms), for the NRR through the first principles high-throughput screening method. A total of 78 TM₁TM₂@C₉N₄ candidates were designed to evaluate their stability, catalytic activity, and selectivity for the NRR. Four TM₁TM₂@C₉N₄ candidates (TM₁TM₂ = NiRu, FeNi, TiNi, and NiZr) with an end-on N₂ adsorption configuration, and two candidates (TM₁TM₂ = TiNi and TiFe) with a side-on adsorption configuration, were screened out with the advantage of suppressing the hydrogen evolution reaction (HER) and exhibiting high NRR activity. Moreover, the catalysts with end-on and side-on N₂ adsorption configurations were determined to favor distal and consecutive reaction pathways, respectively, with favorable limiting potentials of only -0.33 V to -0.53 V. Detailed analysis showed that the N₂ adsorption and activation are primarily ascribed to the strong back-donation interactions between the d-electrons of TM atoms and the anti-orbitals of an N₂ molecule. Our findings pave a way for the rational design and rapid screening of highly active C₉N₄-based catalysts for the NRR.

Computational Study on the Catalytic Performance of Single-Atom Catalysts Anchored on g-CN for Electrochemical Oxidation of Formic Acid

The electrochemical formic acid oxidation reaction (FAOR) has attracted great attention due to its high volumetric energy density and high theoretical efficiency for future portable electronic applications, for which the development of highly efficient and low-cost electrocatalysts is of great significance. In this work, taking single-atom catalysts (SACs) supported on graphitic carbon nitrides (g-CN) as potential catalysts, their catalytic performance for the FAOR was systemically explored by means of density functional theory computations. Our results revealed that the strong hybridization with the unpaired lone electrons of N atoms in the g-CN substrate ensured the high stability of these anchored SACs and endowed them with excellent electrical conductivity. Based on the computed free energy changes of all possible elementary steps, we predicted that a highly efficient FAOR could be achieved on Ru/g-CN with a low limiting potential of −0.15 V along a direct pathway of HCOOH(aq) → HCOOH* → HCOO* → CO2* → CO2(g), in which the formation of HCOO* was identified as the potential-determining step, while the rate-determining step was located at the CO2* formation, with a moderate kinetic barrier of 0.89 eV. Remarkably, the moderate d-band center and polarized charge of the Ru active site caused the Ru/g-CN catalyst to exhibit an optimal binding strength with various reaction intermediates, explaining well its superior FAOR catalytic performance. Hence, the single Ru atom anchored on g-CN could be utilized as a promising SAC for the FAOR, which opens a new avenue to further develop novel catalysts for a sustainable FAOR in formic-acid-based fuel cells.

Urea Production on Metal-Free Dual Silicon Doped C9 N4 Nanosheet Under Ambient Conditions by Electrocatalysis: A First Principles Study

The development of cheap, eco-friendly electrocatalysts for urea synthesis which avoids the traditional nitrogen reduction to form ammonia, is very important to meet our growing demand for urea. Herein, based on density functional theory, we propose a novel electrocatalyst (dual Si doped C₉ N₄ nanosheet) composed of totally environmentally benign non-metal earth abundant elements, which is able to adsorb N₂ and CO₂ together. Reduction of CO₂ to CO happens, which is then inserted into activated N-N bond, and it produces *N(CO)N intermediate, which is the crucial step for urea formation. Eventually following several proton coupled electron transfer processes, urea is formed under ambient conditions. The limiting potential value for urea formation is found to be lower than that of NH₃ formation and HER (hydrogen evolution reaction). Moreover, the faradaic efficiency of our proposed catalyst system is 100 % for urea formation, which suggests greater selectivity of urea formation over other competitive reactions.

Synergistic effect of diatomic Mo-B site confined in graphene-like C2N enables electrocatalytic nitrogen reduction via novel mechanism

Structural modulation of the active site with atomic-level precision is of great importance to meet the activity and selectivity challenges that electrocatalysts are commonly facing. In this work, we have designed a metal (M)-nonmetal diatomic site embedded in graphene-like C₂N (denoted as Mo-B@C₂N), where the electrocatalytic N₂ reduction reaction (eNRR) was thoroughly explored using density functional theory combined with the computational hydrogen electrode method. Compared to M-M diatomic sites, the Mo-B site can generate a pronounced synergistic effect that led to eNRR proceeding via a novel quasi-dissociative reaction mechanism that has not been reported relative to the conventional enzymatic, consecutive, distal, and alternating associative mechanism. This newly uncovered mechanism in which N-N bond scission takes place immediately after the first proton-coupled electron transfer (PCET) step (i.e., *NH-*N + H⁺ + e^- → *NH₂*N) has demonstrated much advantage in the PCET process over the four conventional mechanism in terms of thermodynamic barrier, except that the adsorption of side-on *N₂ seemed thermodynamically unfavorable (ΔG_ads = 0.61 eV). Our results have revealed that the activation of the inert N≡N triple bond is dominated by the π*-backdonation mechanism as a consequence of charge transfers from both the B and Mo sites and, unexpectedly, from the substrate C₂N itself as well. Moreover, the hybrid Mo-B diatomic site demonstrated superior performance over either the Mo-Mo or B-B site for driving eNRR. Our study could provide insight into the delicate relationships among atomic site, substrate, and electrocatalytic performance.

Breaking the Volcano-Shaped Relationship for Highly Efficient Electrocatalytic Nitrogen Reduction: A Computational Guideline

The volcano-shaped relationship is very common in electrocatalytic nitrogen reduction reaction (e-NRR) and is usually caused by the competition between the first and last hydrogenation steps. How to break such a relationship to further improve the catalytic performance remains a great challenge. Herein, using first-principles calculations, we investigate a range of transition-metal (TM)-doped Cu-based single-atom alloys (TM₁-Cu(111)) as catalysts for e-NRR. When the adsorption of N₂ on the catalysts is strong enough, the inert N₂ molecules can be effectively activated for the first hydrogenation step. Meanwhile, the last hydrogenation step is not affected by the scaling relationship and remains easy on all of the catalysts due to the unstable top-site adsorption of NH₂, resulting in the break of the volcano-shaped relationship in e-NRR. Thus, only the first hydrogenation step is identified as the potential determining step. Four TM₁-Cu(111) catalysts (TM = Re, W, Tc, and Mo) are selected as promising catalysts with limiting potential ranging from -0.38 to -0.56 V, showing outstanding e-NRR activity. Besides, the four catalysts also inhibit the competing hydrogen evolution reaction and long-term stability. Our work provides a guideline for breaking the volcano-shaped relationship in e-NRR and significant in the rational design of highly efficient electrocatalysts.

In silico design of single transition metal atom anchored defective boron carbide monolayers as high-performance electrocatalysts for the nitrogen reduction reaction

Development of low-cost and high-efficiency single atom catalysts (SACs) is essential for catalyzing nitrogen reduction reactions (NRR) under ambient conditions. Current SACs suffer from low selectivity and poor activity, making it hard for them to meet the requirements of industrial applications. Here, we present a graphene-like BC₃ monolayer as a substrate for single metal atoms. The catalytic performance of 4d and 5d metal atoms anchored in a vacancy containing BC₃ monolayer for NRR is systematically investigated by first-principles calculations. We find that Re@V_B is outstanding among all candidates, exhibiting high catalytic activity and selectivity, with a low limiting potential of -0.28 V. A new descriptor involving the active site and its environment is proposed, which has a volcano relationship with several factors in the catalytic process, establishing a link between the intrinsic properties of the active site and the catalytic performance. This study opens a new route to designing efficient catalysts with BC₃ as a substrate.