Heterogeneous single-cluster catalysts(Mn_(3),Fe_(3),Co_(3),and Mo_(3))supported on nitrogen-doped graphene for robust electrochemical nitrogen reduction

Electrochemical nitrogen reduction reaction(NRR)is one of the most promising alternatives to the traditional Haber-Bosch process.Designing efficient electrocatalysts is still challenging.Inspired by the recent experimental and theoretical advances on single-cluster catalysts(SCCs),we systematically investigated the catalytic performance of various triple-transition-metal-atom clusters anchored on nitrogen-doped graphene for NRR through density functional theory(DFT)calculation.Among them,Mn_(3)-N4,Fe_(3)-N4,Co_(3)-N4,and Mo_(3)-N4 were screened out as electrocatalysis systems composed of non-noble metal with high activity,selectivity,stability,and feasibility.Particularly,the Co_(3)-N4 possesses the highest activity with a limiting potential of-0.41 V through the enzymatic mechanism.The outstanding performance of Co_(3)-N4 can be attributed to the unique electronic structure leading to strong π backdonation,which is crucial in effective N_(2) activation.This work not only predicts four efficient non-noble metal electrocatalysts for NRR,but also suggest the SCCs can serve as potential candidates for other important electrochemical reactions.

Single-cluster electronics using metallic clusters:Fabrications,regulations,and applications

Metallic clusters,ranging from 1 to 2 nm in size,have emerged as promising candidates for creating nanoelectronic devices at the single-cluster level.With the intermediate quantum properties between metals and semiconductors,these metallic clusters offer an alternative pathway to silicon-based electronics and organic molecules for miniaturized electronics with dimensions below 5 nm.Significant progress has been made in studies of single-cluster electronic devices.However,a clear guide for selecting,synthesizing,and fabricating functional single-cluster electronic devices is still required.This review article provides a comprehensive overview of single-cluster electronic devices,including the mechanisms of electron transport,the fabrication of devices,and the regulations of electron transport properties.Furthermore,we discuss the challenges and future directions for single-cluster electronic devices and their potential applications.

Computational Prediction of Graphdiyne-Supported Three-Atom Single-Cluster Catalysts

While heterogeneous single-atom catalysts(SACs)have achieved great success in the past decade,their application is potentially limited by their simplistic single-atom active centers,which make single-cluster catalysts(SCCs)a natural extension in the domain of heterogeneous catalysis.SCCs with precise numbers of atoms and structural configurations possess SAC merits,yet have greater potential for catalyzing complex reactions and/or bulky reactants.Through systematic quantum-chemical studies and computational screening,we report here the rational design of transition metal three-atom clusters anchored on graphdiyne(GDY)as a novel kind of stable SCC with great promise for efficient and atomically precise heterogenous catalysis.By investigating their structure and catalytic performance for the oxygen reduction reaction,the hydrogen evolution reaction,and the CO_(2)reduction reaction,we have provided theoretical guidelines for their potential applications as heterogeneous catalysts.These GDY-supported three-atom SCCs provide an ideal benchmark scaffold for rational design of atomically precise heterogeneous catalysts for industrially important chemical reactions.

Precious trimetallic single-cluster catalysts for oxygen and hydrogen electrocatalytic reactions:Theoretical considerations

Single cluster catalysts(SCCs),which exhibit remarkable catalytic performance due to their high metal loading and synergy effect between metal atoms,have attracted great attention in research.Herein,by means of density functional theory calculations,the oxygen reduction reaction(ORR),oxygen evolution reaction(OER),hydrogen evolution reaction(HER)performances of precious metal(Pt,Pd,Rh,Ir)trimetallic single-cluster electrocatalyst(U_(x)V_(y)W_(z)-NG)are investigated.The calculation results show that Pt,Pd,Ir have significant effect on ORR,OER,HER,respectively,all the calculated U_(x)V_(y)W_(z)-NG structures are thermodynamically stable due to the negative formation energies and binding energies.The Pt_(3)-NG,Pd_(3)-NG,Ir_(3)-NG show the lowest ORR,OER,HER overpotentials of 0.63,0.77,−0.02 V,respectively,among all combinations of U_(x)V_(y)W_(z)-NG.These overpotentials are lower than that of precious metal single atom catalysts(SACs),which indicate better activities of precious trimetallic SCCs than those of SACs.The electronic structure reveals that the O-2p orbital shows strong hybridization strength with Pt-3d orbitals in the system of OH adsorbed Pt_(3)-NG and thus facilitates the electrocatalytic reactions.The results are helpful for the rational design of high-performance triatomic catalysts.

Halide Anchors for Single-Cluster Electronics

Due to their unique electronic structure,well-defined metal clusters at the atomic level are promising materials for single-cluster electronics.However,coupling between the electrode and the cluster remains challenging mainly due to the coverage of bulky ligands on the noble clusters.Using the scanning tunneling microscopy break junction(STM-BJ)technique,we have developed a“direct contact”approach to fabrication and investigation of the charge transport through single-cluster junctions of AgCu bimetallic metal clusterswith different halide anchors.Wefound that the electrodes could make contact directly with the surface halides of the single-cluster junctions and experience different contact resistance from different halogen atoms.Experiments and calculations reveal that the halide anchors provided efficient coupling between the cluster and the electrode,and the enhanced coupling with various halide anchors promoted electron transport and improved transmission probability.Our work offers a“direct contact”strategy for interface design between clusters of noble metals and electrodes,an essential step in progress toward single-cluster electronics.

TM_(3)(TM=V,Fe,Mo,W)single-cluster catalyst confined on porous BN for electrocatalytic nitrogen reduction

Confined metal clusters as sub-nanometer reactors for electrocatalytic N_(2) reduction reaction(eNRR)have received increasing attention due to the unique metal-metal interaction and higher activity than singleatom catalysts.Herein,the inspiration of the superior capacitance and unique microenvironment with regular surface cavities of the porous boron nitride(p-BN)nanosheets,we systematically studied the catalytic activity for NRR of transition-metal single-clusters in the triplet form(V_(3),Fe_(3),Mo_(3) and W_(3))confined in the surface cavities of the p-BN sheets by spin-polarized density functional theory(DFT)calculations.After a two-step screening strategy,Mo_(3)@p-BN was found to have high catalytic activity and selectivity with a rather low limiting potential(-0.34 V)for the NRR.The anchored Mo_(3) singlecluster can be stably embedded on the surface cavities of the substrate preventing the diffusion of the active Mo atoms.More importantly,the Mo atoms in the Mo_(3) single-cluster would act as“cache”to accelerate electron transfer between active metal centers and nitrogen-containing intermediates via the intimate Mo-Mo interactions.The cooperation of Mo atoms can also provide a large number of occupied and unoccupied d orbitals to make the"donation-backdonation"mechanism more effective.This work not only provides a quite promising electrocatalyst for NRR,but also brings new insights into the rational design of triple-atom NRR catalysts.

Unveiling the size effect of nitrogen-doped carbon-supported copper-based catalysts on nitrate-to-ammonia electroreduction

The electrocatalytic nitrate reduction reaction(NitRR)represents a promising approach toward achieving economically and environmentally sustainable ammonia.However,it remains a challenge to regulate the size effect of electrocatalysts to optimize the catalytic activity and ammonia selectivity.Herein,the Cu-based catalysts were tailored at the atomic level to exhibit a size gradient ranging from single-atom catalysts(SACs,0.15–0.35 nm)to single-cluster catalysts(SCCs,1.0–2.8 nm)and nanoparticles(NPs,20–30 nm),with the aim of studying the size effect for the NO_(3)^(-)-to-NH_(3) reduction reaction.Especially,the Cu SCCs exhibit enhanced metal–substrate and metal–metal interactions by taking advantageous features of Cu SACs and Cu NPs.Thus,Cu SCCs achieve exceptional electrocatalytic performance for the NitRR with a maximum Faradaic efficiency of ca.96%NH_(3)and the largest yield rate of ca.1.99 mg·h^(-1)·cm^(-2) at-0.5 V vs.reversible hydrogen electrode(RHE).The theoretical calculation further reveals the size effect and coordination environment on the high catalytic activity and selectivity for the NitRR.This work provides a promising various size-controlled design strategy for aerogel-based catalysts effectively applied in various electrocatalytic reactions.

超越原子可视化—利用扫描透射电子显微镜表征双原子单团簇催化剂

本研究利用扫描透射电子显微镜(STEM)表征了碳掺杂氮负载的FeFe和CoFe双原子单团簇催化剂.同时本工作开发了一个STEM图像处理程序,以精准识别原子的位置并得到可能的原子对中原子之间的投影距离.大数据分析结果显示CoFe和FeFe原子对的距离均呈现三峰分布,对应于模拟得到的多种稳定的原子结构.我们的工作为通过STEM图像的大数据统计和相关理论模拟直接揭示双原子单团簇催化剂中双原子位点的可能原子构型提供了一条途径.

单团簇催化剂在乙炔半加氢反应中的优异反应性

载体上孤立的Pd原子作为乙炔半加氢反应的催化活性位点,由于具有独特的反应性和高效的金属利用率而备受关注.特别是在金属氧化物表面的不同位点掺杂Pd单原子,可以通过调节其局部配位环境来调控其电子和催化性能.本文采用密度泛函理论计算,研究了TiO_(2)负载Pd单原子的局域配位环境对Pd_(1)/TiO_(2)催化剂上乙炔半加氢反应的活性和选择性的影响.综合考虑反应活性和选择性,发现具有负电荷Pd^(δ-)位点的Pd_(1)Ti_(3)/TiO_(2)四原子单团簇催化剂展现出优异的催化性能.此外,活性和选择性与表面性质如d-带中心指数和表面功函数等密切相关.本文为未来设计可还原氧化物载体上的高效单团簇催化剂以用于类似的多相催化反应提供了理论参考.

Transition metal clusters with precise numbers of atoms anchored on graphdiyne as multifunctional electrocatalysts for OER/ORR/HER:a computational study

Subnanometer metal clusters play an increasingly important role in heterogeneous catalysis due to their high catalytic activity and selectivity.In this work,by means of the density functional theory(DFT) calculations,the catalytic activities of transition metal clusters with precise numbers of atoms supported on graphdiyne(TM_(1-4)@GDY,TM=V,Cr,Mn,Fe,Co,Ni,Cu,Ru,Rh,Pd,Ir,Pt) were investigated for oxygen evolution reactions(OER),oxygen reduction reactions(ORR) and hydrogen evolution reactions(HER).The computed results reveal that the Pd_(2),Pd_(4) and Pt_(1) anchored graphdiyne can serve as trifunctional catalysts for OER/ORR/HER with the overpotentials of 0.49/0.37/0.06,0.45/0.33/0.12 and 0.37/0.43/0.01 V,respectively,while Pd_(1) and Pt_(2)@graphdiyne can exhibit excellent catalytic performance for water splitting(OER/HER) with the overpotentials of 0.55/0.17 and 0.43/0.03 V.In addition,Ni_(1) and Pd_(3) anchored GDY can perform as bifunctional catalysts for metal-air cells(OER/ORR) and fuels cells(ORR/HER) with the overpotentials of 0.34/0.32 and 0.42/0.04 V,respectively.Thus,by precisely controlling the numbers of atoms in clusters,the TM_(1-4) anchored graphdiyne can serve as promising multifunctional electrocatalysts for OER/ORR/HER,which may provide an instructive strategy to design catalysts for the energy conversation and storage devices.