Study On Structure And Electrocatalytic Performance Of Supported Single-atom Catalysts

In recent years,single-atom catalysts have attracted extensive research interest in the field of catalytic science.As a special supported metal catalyst,all metal components on the matrix exist in the form of monoatomic dispersion,leading to many unexpected physicochemical properties,such as quantum size effect,unsaturated coordinationenvironment,etc.,which are significantly different from nano or sub-nanometer particles,and accounts for the superior catalytic performance.Maenwhile,single-atom catalysts have extremely high atomic utilization efficiency and have great potential for rational utilization of metal resources.In addition,the ideal structure of the single-atom catalyst provides an ideal model for studying the catalytic mechanism of the surface interface in the catalytic reaction.1.single-atom Cu1/N-Graphene for electrocatalytic oxygen reduction reactionM-N-C are ideal alternative to platinum catalysts for oxygen reduction(ORR)catalysts,and their easily regulated high specific surface area can significantly increase the number of active sites exposed and the mass transfer rate of the catalyst.On the other hand,heterogeneous heteroatoms in non-noble metal carbon-based materials can serve as anchor sites for coordination and confinement of single metal atoms,thereby stabilizing metal monoatoms and improving catalytic activity and stability.In addition,M-C-N is more resistant to CO poison,which is critical to improving catalysts’ life.In this paper,a monodisperse Cu catalyst was designed by coordination design strategy,and the single-atom catalyst was successfully synthesized by a simple one-step pyrolysis process,in which atom-dispersed Cu atoms were confined in N-doped graphene.Combined with the spherical aberration correction HAADF-STEM and the synchrotron radiation XAFS,validates that the intrinsically active center is composed of a mixture of Cu-N2 and Cu-N4 moieties.Further calculation and analysis shows that the proportions of Cu-N2 and Cu-N4 configurations are 65%and 35%,respectively.The designed catalyst exhibits outstanding ORR activity with Eonsetand half-wave E1/2potential at 0.869V and 0.779V respectively,and a smaller Tafel slope of 74 mV decade-1,superior to the commercial Pt/C catalysts.2.single-atom Pt1/CoNS for electrocatalytic Oxygen evolution reactionOxygen evolution reaction plays a crucial role in renewable energy technologies.It exhibits a high reaction potential and a slow reaction kinetics,which greatly limits the overall efficiency of the water-decomposition hydrogen production reaction,which stimulates the design of a highly efficient and stable oxygen production catalyst.single-atom catalysts have extremely high atomic utilization,active sites are completely exposed,and metal-support interactions can effectively regulate the intrinsic properties of active centers,and are ideal materials for replacing traditional precious metal catalysts.In this paper,a single-atom Pt catalyst was designed and prepared for the study of OER.Pt atoms were anchored on ultra-thin two-dimensional cobalt nanosheets,combined with X-ray photoelectron spectroscopy and synchrotron XAFS characterization techniques,revealing that Pt atoms in Pt1/Co NS samples are in a substitutional position on the Co matrix.The catalyst exhibits excellent OER performance,the current density reaches 400 mA.cm-2 at overpotential of 395 mV,which is much higher than the pure Co nanosheets and commercial RuO2.This study demonstrates that the use of single-atom modified catalysts has huge potential for further optimization and improvement of catalytic performance of electrocatalytic OER.