Defect Engineering-based Modification Of Nano-Co₃O₄ For Water Electrolysis

Defect engineering,as a new strategy for adjusting electronic structure and interface coordination,has gradually emerged in recent years.In particular,oxygen vacancies with low formation energy can flexibly and efficiently control some properties of materials,and are used in catalysis,corrosion protection,and corrosion protection.Advanced technologies such as thermal coatings,sensors,and microelectronics have been continuously applied.In addition,the unique electronic structure of the defect site provides unlimited possibilities for further modification of the material surface,which has huge application prospects.In this paper,liquid metal potassium-sodium alloy is used as a reducing agent,and a variety of defect oxides can be quickly prepared at room temperature through a liquid phase shear assisted method.In order to verify the usable potential of this synthesis strategy,we selected defective Co₃O₄as the model system and studied its oxygen evolution reaction（OER）performance.On this basis,the method of shear-assisted reduction is further used to grow metal nanoparticles on the surface of the defect oxide to construct a heterostructure to improve the OER performance of the material.On the other hand,by using the high activity of defect sites to induce selective doping of phosphorus elements,a novel dual-functional catalyst with nanosheet structure and capable of overall water splitting under alkaline conditions was prepared.The specific research contents are as follows:1.Defect engineering in oxides can effectively adjust the valence of ions and provide more active centers for electrocatalytic reactions.However,the production of oxygen defects often requires a higher reaction temperature and a longer reaction time.Therefore,we have developed a simple and universal method to create defects on the surface of metal oxides such as Co₃O₄,Zn O,Sn O₂and Ce O₂by using a highly active liquid sodium potassium（Na-K）alloy as a reducing agent at room temperature.In order to verify the usable potential of this synthetic strategy,we used defective Co₃O₄as a model system and studied its oxygen evolution reaction（OER）performance.The results show that oxygen vacancies have a significant promotion effect on OER activity.The starting potential is1.54 V,and the Tafel slope is 47.9 m V/Dec,which is much lower than the original Co₃O₄nanoparticles.Our method of producing defects in oxides can be used in many other related applications.2.A simple and rapid method for constructing oxide/metal heterojunctions is proposed.Through the auxiliary reduction system of potassium sodium alloy as a high-efficiency reducing agent,metal nanoparticles can be loaded on the surface of the defective Co₃O_4-xin a very short time（1 min）to modify the interface of the defective oxide,and the heterogeneous interface between metal nanoparticles and defect oxides becomes a new active site.The material after reconstructing the interface not only shows better OER activity,but also has better stability under high current state.3.A method to construct a two-dimensional heterostructure bifunctional electrocatalyst by oxygen vacancy induced phosphorus doping is proposed.The total hydrolysis reaction has attracted much attention as an attractive method for hydrogen fuel production.In this study,we developed a phosphorus-doped nano-sheet Co₃O_4-x-P as a catalyst for high-efficiency full hydrolysis in an alkaline environment.We use the high activity of oxygen vacancies to easily induce phosphorus doping and synthesize a unique nanosheet structure with rich heterogeneous interfaces.Therefore,the catalyst exhibits significant HER and OER catalytic activity and reliable stability in alkaline environments.And the complete hydrolysis reaction was realized at 1.64 V.