Modulation Of Surface Structure And Oxygen Precipitation Reaction Performance Of Nickel-Based Sulfide Catalysts By Anions

Electrochemical hydrolysis is one of the more environmentally friendly and promising technologies for hydrogen production,which is an important strategy to achieve green industry and solve the problem of energy crisis.The main reason that restricts the development of electrolytic water technology is the slow reaction kinetics and high reaction energy base of oxygen precipitation reaction,so the search and construction of efficient,stable and cheap catalysts for oxygen precipitation reaction is the key to achieve efficient hydrogen production.In this paper,we use nickel-based sulfide catalysts as pre-catalysts,and investigate the modulation of the surface structure and oxygen precipitation reaction performance of nickel-based sulfide catalysts by anions using the density flooding theory（DFT）method based on first principles.The main contents include:（1）Modulation of the surface structure of nickel-based thiocyanate catalysts by anions.Pourbaix diagrams were constructed and the evolution order of the stable species of the precatalyst system with increasing voltage in a strongly alkaline environment（p H=14）was Ni M_x（M=S/Se/Te）→Ni（OH）2→Ni OOH.The ease of oxidation to Ni（OH）₂on the surface of the three precatalysts was the easiest for NiS₂（U≤0.452 V）,NiSe2（U≤1.035 V）,and Ni Te（U≤2.064 V）.During the reconstitution process,the precipitated anions（S/Se/Te）are oxidized to the corresponding acid ions and adsorbed on the surface of the Ni（OH）₂layer.Comparing the adsorption energies of various adsorption modes（surface physical adsorption,intercalation physical adsorption,vacancy adsorption and chemical bonding adsorption）,all three acid ions tend to be adsorbed in a chemical bonding manner.Due to the modulation of the anion,the value of the applied voltage required for the oxidation to produce Ni OOH was reduced from 2.193 V（Ni（OH）₂）to 1.93 V（Ni（OH）₂-SO₄）,2.032 V（Ni（OH）₂-Se O₄）,and 1.913 V（Ni（OH）₂-Te O₃）.（2）Theoretical study on the performance of single anion group-regulated oxygen precipitation reaction of hydroxy nickel oxide.The anions（SO₄/Se O₄/Te O₃）can be adsorbed on different crystallographic surfaces of Ni OOH for OER reactions by different reaction mechanisms.For the OER reaction of AEM mechanism,the modification ability of SO₄is weaker（ηdecreases from 1.064 V to 1.032 V）.For the OER reaction of the unit-site LOM mechanism,SO₄/Se O₄can both directly participate in the reaction as a proton acceptor,promoting the dehydrogenation and oxidation of*OH and*OOH intermediates;and also change the electronic structure of the surrounding Ni atoms,promoting*OH adsorption,withηdecreasing to 0.436V/0.654 V.Although Te O₃fails to act as a proton acceptor,it also promotes*OH adsorption,withηdecreasing to For the OER reaction of the doouble-site LOM mechanism,SO₄/Se O₄/Te O₃can promote the OER reaction by facilitating O-O coupling and O₂desorption,and*OH adsorption withηdecreasing to 0.655 V,0.932 V and 0.788 V,respectively,and its modulation of the electronic structure of the surrounding Ni atoms effectively increases the OER catalytic activity of Ni OOH.（3）Theoretical study on the modulation of the performance of the oxygen precipitation reaction of nickel hydroxide by double anionic groups.The introduction of F ions in Ni OOH-SO₄catalysts can further modulate their OER performance.For the OER reaction in the unit-site LOM mechanism,the synergistic effect of SO₄and F ions makes the adsorption of*OH intermediates easier,and the catalytic activity of each active site increases,withηdown to 0.348 V.For the OER reaction in the double-site LOM mechanism,F ions exhibit a certain inhibitory effect:the doping of F ions further reduces the number of active sites and repels OH^-.and repulsion of OH^-,making the overpotential higher and the dehydrogenation and oxidation of*OH intermediates more difficult.The doping of double or multiple anions screens the reaction mechanism of OER catalysts.In this paper,it is shown that the presence of anions has a good ability to regulate the surface structure and oxygen precipitation reaction performance of nickel-based sulfide compounds,and the mechanism of the anions’action is elaborated from the perspectives of surface structure and reaction activity,respectively,to provide some theoretical guidance for the subsequent design and modification of efficient and low-cost OER catalysts.