First-principles Study Of Electrocatalytic Reactions Based On Two-dimensional Materials

With the decayed amount of traditional fossil energy and the related environment problem,a clean and renewable energy source is firmly demanded.Proton membrane fuel cells?PEMFC?and hydrogen energy is promising because it is sourced by water and final product is water.For catalyzing the reaction in the PEMFC efficiently,Platinum,Pt-based materials are employed commercially.However,the development of PEMFC is increasingly hindered by high cost of Pt-based catalyst for its high price and limited content.Therefore,an electrocatalyst that is inexpensive and has high catalytic activity similar to or even prior to Pt is needed.In this paper,we used first-principles calculations and theoretical analysis to study the effect of doping?N,S atoms?,lattice strain and atomic defects on the catalytic performance of graphene.In order to obtain a catalyst with good ORR catalytic activity or HER catalytic activity,the specific studies are as follows:?1?We report the improved catalytic activity for ORR of the N-doped graphene?SNG?with localized lattice strain based on the first-principles calculations.Our results reveal the synergistic catalytic mechanism of straining and nitrogen doping?N-doping?,which can effectively promote the ORR catalytic performance compared with N-doped graphene?NG?,strained graphene?SG?,or pristine graphene?G?sample.It is found that N-doping can change the electron states near fermi level of C atom from inoccupation to occupation and thus improving the conductivity.Alternatively,straining can enhance the electronic orbit coupling between the substrate and the adsorbed O₂.?2?Based on first-principles calculations,we studied the HER catalytic performance of structures that N and S atoms doped defective graphene?NG,SG?and N,S co-doped defective graphene?NSG?.We find that,compared to the NG structure and the NSG structure,the SG structure is relatively moderate in both the adsorption energy of hydrogen atoms and the value of?G_H*,which is neither the highest nor the lowest.Moreover,the?G_H*of the SG structure is closest to 0,only-0.0737 e V,which shows HER catalytic activity of SG comparable to Pt.