Amorphous Nickel Sulfoselenide For The Electrocatalysis Of Hydrogen Evolution Reaction And Urea Oxidation Reaction In Alkaline Media

Hydrogen energy has attracted wide attention due to its advantages of high efficiency,cleanliness,abundant resources,convenient storage and transportation and wide application range.Water electrolysis is regarded as the most promising hydrogen production method due to its rich raw materials,high purity of hydrogen produced and controlled reaction rate.Hydrogen evolution reaction（HER）is the key reaction of electrolysis water hydrogen production technology.The development of noble metal-free and high-performance HER electrocatalysts is essential for the large-scale application of water electrolysis to produce hydrogen.In this paper,an amorphous nickel sulfoselenide nanosheet array with excellent activity and stability was prepared by ion exchange.It was found that nickel sulfoselenide had excellent HER performance in alkaline media.The overpotential at 10 and 100 m A cm^-2 for nickel sulfoselenide was 98 and206 m V（1 M KOH）.Compared with nickel selenide,the catalytic activity of nickel sulfoselenide was greatly enhanced by the introduction of S.Compared with nickel sulfide,the activity of unit S in nickel sulfoselenide was significantly increased.According to density functional theory（DFT）calculation,it was found that nickel sulfoselenide had the highest adsorption energy of H₂O and the optimal free energy of H*.In addition,Ni-S-Se/NF had a larger active area and hydrophobic/aerophobic properties,which was also beneficial to improve HER activity.Overall water splitting is composed of HER at the cathode and oxygen evolution reaction（OER）at the anode.Compared with HER,the OER reaction kinetics is slower and the overpotential is higher.Therefore,it is an effective method to improve the efficiency of hydrogen production by electrolyzed water to find a reaction with lower potential and more valuable than OER.Replacing OER with urea oxidation reaction（UOR）can significantly reduce the anode potential,thereby improving the energy efficiency of electrolytic hydrogen production.At the same time,it can remove urea in water and purify water quality.In this paper,amorphous nickel sulfoselenide was used for UOR in alkaline media,and showed excellent UOR activity and stability.It was found that the active species of amorphous nickel sulfoselenide in UOR was Ni OOH,and the main oxidation products were N₂ and CNO^-.Further,amorphous nickel sulfoselenide was used as cathode and anode electrocatalyst to assemble a urea electrolyser.It was proved that the urea electrolyser had excellent performance,and the corresponding voltages at 10 and 100 m A cm^-2 were only 1.43 and 1.59 V（1 M KOH+0.5 M Urea）,significantly lower than the corresponding water electrolysis.The above results prove that the amorphous nickel sulfoselenide is a bifunctional catalyst with outstanding HER and UOR performance.The present work provides a strategy to prepare amorphous sulfoselenides and give more insights into the reaction mechanisms of HER and UOR on sulfoselenides.