The Electrocatalytic Hydrogen Evolution Performance Of Low Dimensional Materials:First-principles Studies

There are many ways to produce hydrogen in industry,among which water electrolysis via the hydrogen evolution reaction（HER）is an efficient and pollution-free production method,which is expected to become the main force of hydrogen energy development in the future.Noble metals,such as platinum,are recognized as highly efficient electrocatalysts for HER,but their high cost and scarcity seriously hinder the large-scale commercial applications.Therefore,the pursuit of cheap,environmentally friendly and efficient catalysts has become a constant goal in the field of electrocatalytic hydrogen evolution.Due to the excellent structural properties and electronic properties of 2D materials,effective electrocatalysts have been selected from two-dimensional materials.Recently,new 2D materials black phosphorus and black arsenic have attracted attention.Black phosphorus has been extensively studied in the field of electrocatalytic hydrogen evolution due to its high carrier mobility,anisotropy,large specific surface area and band gap that can be adjusted with the number of layers.However,the electrocatalytic activity of pristine black phosphorus in hydrogen evolution reaction is very weak,which limits its application in the field of electrocatalysis.Black arsenic also has excellent properties similar to that of black phosphorus,and is considered to own broad development potential in the field of electrocatalysis.However,there is no relevant description of black arsenic as a catalyst of hydrogen evolution reaction either experimentally or theoretically.In order to promote the application of black phosphorus in the field of electrocatalysis and theoretically predict the activity of black arsenic as a catalyst for HER,we study the HER electrocatalytic performance of pristine black phosphorus and black arsenic and improve their catalytic activity through doping or adsorption,which are also the innovation and focus of this paper.The main contents of this paper are as follows:ⅰ.We systematically use the density functional theory（DFT）caculations to study the HER catalytic performance of black phosphorous（phosphorene）and the influence of doped atoms and adsorption groups.For electrochemical catalysts,moderate hydrogen adsorption intensity（not too strong or not too weak）is the key to determine the catalytic performance of hydrogen evolution reaction.We use the Gibbs free energy of adsorption of hydrogen(（35）G_H*)as the basis of determining HER activity.We find that the interaction between the doped atom/functional groups and the phosphorene substrate can significantly enhance the influence of the electron states near the Fermi energy level,and thus regulate the phosphorene’s HER catalytic activity.O doping and adsorption NH₂/OH groups can improve the catalytic performance of phosphorene plane and edges,（35）G_H*can be reduced to about 0.14 eV.ⅱ.We study the HER catalytic performance of monolayer black arsenic on the basis of first-principles calculations.The pristine monolayer black arsenic shows poor catalytic performance because the binding strength of hydrogen atoms is too weak.We chemically regulate the HER catalytic performance of black arsenic by doping heteroatoms.Five different doping atoms（N,S,C,O and P）are inserted into monolayer black arsenic,and it is found that O atom is more likely to be embedded in the lattice of monolayer black arsenic with the most stable defect energy.The doped O atom can increase the binding strength of H*to an appropriate degree and greatly improve the HER catalytic performance.The O_As at the basal plane of monolayer black arsenic can reduce the（35）G_H*to as low as 0.044 eV,which is quite competitive with Pt(（35）G_H*=-0.090eV),showing its excellent HER catalytic performance.It is noted that embedded O shows better catalytic activity at the basal plane compared to that at the edge site,which has the advantage of maximizing the number of active sites.Clustering of O_Asin monolayer black arsenic will slightly degrade the HER performance.