Improving Catalytic Performance Of MXene-based Materials Via Surface Modifications

Proton exchange membrane fuel cells(PEMFCs)are considered to be the first choice for replacing fossil energy sources and solving energy crises and environmental problems because of their clean,high-efficiency,and non-polluting advantages.So far,almost all current PEMFCs use Pt/C to catalyze the reactions on the electrodes,in which carbon is used as a conductor and Pt particles are used as a catalyst.However,due to the high cost,poor stability,sluggish ORR kinetics,easy corrosion and CO poisoning of Pt/C,the large-scale commercial application of PEMFCs has been inhibited.Since Ti₃C₂T_x was first reported in 2011,transition metal carbide/carbonitride/nitride(MXene)has become a large and growing family of 2D materials.As a new two-dimensional material,MXene has many unique properties.For example,metalic conductivity,large surface area,adjustable structure,and hydrophilicity,which make it promising to be used in energy conversion and storage,electromagnetic interference shielding,catalysis,sensors,etc.In addition,unlike other two-dimensional materials,the abundant functional groups on the surface of MXene can be chemically modified,making MXenes's physical and chemical properties highly tunable.Based on density functional theory,we systematically studied the effects of surface modification(functional group modification,heteroatom doping,etc.)on the topological structure,electronic structure,and catalytic performance of MXenes,and further revealed its internal regulation and reaction mechanism.The research results can provide theoretical guidance for the design of high-performance MXene-based electrode catalytic materials.The main innovations are as follows:(1)By modifying the surface of MXene by loading transition metal single atoms on V₂CO₂ MXene with O vacancies(Ov/V₂CO₂).We proposed 6 criterons to efficiently screen MXene-based single-atom catalysts with high stability and good catalytic performance.(2)By studying the modifying morphology,electronic structure,stability,and ORR catalytic activity of a series of transition metal atoms(Ni,Pd,Pt,Cu,Ag,Au)deposited on V₂C MXene,we illustrated the mechanism of interaction between transition metal atoms and V₂C MXene at the atomic level,which provides an effective way for rational design of ORR catalysts with optimized electronic structure.(3)By studying the physical and chemical properties of Pt monolayer deposited Ti₂C,Zr₂C,Hf₂C,V₂C,Nb₂C,Ta₂C,Cr₂C,Mo₂C,and W₂C,we proposed and verified a descriptor for designing stable TM/MXenes composites.This work proposed a new strategy for efficiently searching and designing excellent ORR/OER catalysts with TM/MXene.In summary,this work investigated the morphology,electronic structure and catalytic performance of MXene-based catalysts tuned by surface modifications.Besides,we revealed the metal-support interaction mechanism and regulation rules,which provides a new design strategy for MXene-based high-performance catalysts at the cathode of PEMFCs.Meanwhile,we hope the results can provide theoretical guidance for related experimental work.