| With the overexploitation of fossil energy and a series of environmental pollution caused by the use of it,the development of a clean and efficient renewable energy has become an inevitable trend of future energy development.Among a range of energy sources,hydrogen(H2)has attracted widespread attention due to its non-polluting combustion process and high calorific value of combustion.At present,electrolysis of aquatic hydrogen is one of the main means of industrial hydrogen production.In practical applications,electrolyzed water is mainly divided into two and a half reactions:hydrogen evolution reaction and oxygen evolution reaction(HER/OER).Hydrogen evolution and oxygen evolution(HER/OER)catalysts are important components of highly efficient electrocatalytic batteries.In order to obtain better electrical performance of hydrogen evolution reaction and oxygen evolution reaction,adjusting the electronic structure of the electrocatalyst by some means,and orbital regulation during the reaction process is a feasible strategy to achieve efficient electrocatalytic efficiency.This paper is based on first-principles calculations and density functional theory research methods:a series of chemical properties such as electronic structure,band structure,stability and other chemical properties of nickel sulfide(Ni3S2)are studied,and its efficient water splitting efficiency is achieved by using metal doping.The main contents are as follows:(1)Cost-efficient bifunctional electrocatalysts with good stability and high activity are in great demand to replace noble-metal-based catalysts for overall water-splitting.Ni3S2 has been considered a suitable electrocatalyst for either the hydrogen evolution reaction(HER)or the oxygen evolution reaction(OER)owing to its good conductivity and stability,but high performance remains a challenge.Based on density functional theory calculations,we propose a practical 3d-transition-metal(TM=Mn,Fe and C o)doping to enhance the catalytic performance for both HER and OER on the Ni3S2(101)facet.The enhancement originatesfrom TM-doping-induced charge rearrangement and charge transfer,which increases the surface activity and promotes catalytic behavior.In particular,Mn-doped Ni3S2 shows good bifunctional catalytic activity because it possesses more active sites,reduced hydrogen adsorption free energy for HER and low overpotential for OER.Importantly,this work not only provides a feasible means to design efficient bifunctional electrocatalysts for overall water-splitting but also provides insights into the mechanism of improving catalytic behavior.(2)Effect of orbit on the performance of electrocatalytic oxygen production-The role of magnetism.Among a series of electrocatalytic materials,RuO2,IrO2 and other noble metal material oxides are recognized to have the best oxygen production performance,and their overpotential is close to the ideal equilibrium potential of 1.23 V.These materials all possess intrinsic magnetism,and whether the excellent OER properties of these noble metal oxides are related to their magnetism has not been reported.In our previous work,we found that for the originally non-magnetic material Ni3S2,some magnetic doping systems showed better OER effect after doping part of the transition metal.Then,based on first-principles calculations,we carried out metal doping to improve the OER activity of Ni3S2(101)plane,revealing that the magnetism of the doping system comes from the doped atoms,and the bond cooperation of the doped atoms mainly comes from the el orbitals.Magnetism has no direct effect on the performance of OER,but in this system,magnetism mainly comes from the exchange splitting energy caused by doping atoms related to el orbitals.The Mo doping for the active site and the oxygen-containing intermediate bond cooperation in the process of the final step is due to the stronger interaction between the el orbitals,so the OER reaction overpotential is further reduced.This paper not only provides a feasible method for designing excellent OER catalyst,but also reveals its intrinsic physical mechanism. |
PDF Full Text Request