Surface Modification Of Two-Dimensional Nano Materials For Electrocatalysis:A DFT Study

With the increasing shortage of traditional fossil fuels and environmental pollution,all countries in the world are actively looking for renewable clean energy and new energy storage and conversion technologies.Electrocatalytic reactions,including hydrogen evolution reaction(HER),oxygen evolution reaction(OER)and oxygen reduction reaction(ORR),are the core of new energy storage and conversion technologies such as electrolysis of water,metal-air batteries and fuel cells.However,the slow reaction kinetics and large overpotential in electrocatalytic reaction lead to low efficiency,so it is necessary to improve the reaction kinetics and reduce the overpotential.At present,noble metal Pt and its derivatives are the electrocatalysts with the highest catalytic activity.However,the limited content and high cost of noble metal catalysts limit its large-scale commercial application.Therefore,it is necessary to develop more stable,efficient and low-cost electrocatalysts to replace noble metal.In recent years,the rise of two-dimensional(2D)materials has attracted wide attention.Due to their unique physicochemical properties,they show great potential in electrocatalysis,and open a new avenue for the search for excellent electrocatalysts.This paper aims to focus on new energy storage and conversion technologies through first-principles calculations based on density functional theory(DFT)and the structural properties of MXene and phosphorene materials.Design and develop HER,OER/ORR monofunctional or bifunctional electrocatalysts through surface modification methods such as non-metallic atom doping and supporting metal single atoms.The main research contents are as follows:(1)Based on first-principles calculations,the electronic structure and HER catalytic performance of Ti3C2O2(X-Ti3C2O2)doped with non-metallic atoms(B,C,N,P and S)have been systematically studied.The presence of non-metallic atoms regulates the electronic structure of Ti3C2O2,and increases the electron occupancy rate near the Fermi level of Ti3C2O2,thus effectively improving the electrical conductivity.The downward shift of the pz band center of O atoms(away from the Fermi energy level)leads to an increase in the electron occupancy of the anti-bonding orbital(σ*),which weakens the interaction between H and O,and promotes the increase of ΔGH and closer to 0,thus improving the catalytic activity of Ti3C2O2.The ΔGH of N-Ti3C2O2 is only-0.01 eV(hydrogen coverage θ=1/9 ML),which exceeds most noble metal catalysts,and is expected to be widely used as HER catalyst in water electrolysis devices.(2)Based on first-principles calculations,we constructed the single-atom model supported by phosphoene(TM@BP and TM-BP),and screened out highly efficient OER/ORR dualfunction catalysts.The 3d orbitals of metal atoms are strongly hybridized with the 2p orbitals of P atoms,resulting in the reduction of the band gap or the transformation from semiconductor to conductor of phosphorene,thus significantly improving the electrical conductivity.The d band electrons of metal atoms can adjust the interaction between intermediates and catalysts,and make them have suitable bonding strength,effectively reducing the reaction overpotential.The calculation results show that TM@BP and TM-BP can be used as OER/ORR bifunctional catalysts.In particular,Ni@BP and Ni-BP have OER overpotential of 0.56 V and 0.16 V,and ORR overpotential of 0.57 V and 0.31 V,respectively,showing catalytic performance comparable to noble metal catalysts.They are expected to be widely used as OER/ORR dualfunction catalysts in metal-air batteries.