Reconstruction Modification And Catalytic Applications Of Transition Metal Oxides And Sulfides

Given the increasing demands for energy and the growing awareness of environmental protection,the development of clean and renewable energy has become essential for the sustainable utilization of energy.As the most critical aspect of energy conversion and storage,catalytic reactions have been extensively studied.Electrolytic water splitting reaction and oxygen reduction reaction,in particular,are widely used in various applications.However,these reactions often generate significant overpotential and result in high energy loss due to their slow four-electron transfer process,which restricts the entire catalytic reaction.On the other hand,methane dry reforming technology can convert two greenhouse gases,methane and carbon dioxide,into industrially required syngas（carbon monoxide and hydrogen）,providing a hydrogen production route with both economic and environmental benefits.Despite its potential,the high industrial costs have limited its widespread adoption.Therefore,designing and synthesizing low-cost,high-efficiency non-precious metal catalysts has become a hot topic in the field of catalysis.This paper examined the activity and stability of catalysts under industrial alkaline water electrolysis conditions,focusing on the structural characteristics and the applicability of perovskite oxides in industrial settings.Then,metal oxides and sulfides were taken as the research objects,and their applications in electrocatalytic oxygen evolution,oxygen reduction reaction and methane dry reforming reaction were studied,respectively.Perovskite oxides have emerged as one of the most promising non-noble metal water oxidation catalysts due to their abundant elemental composition and structural tunability.In addition,transition metal sulfides exhibit unique physical and chemical properties in energy storage applications including water electrolysis cells,fuel cells,and supercapacitors due to their rich phase types and superiority in nanoengineering construction.However,the effective utilization of these catalysts is often hindered by several issues,such as surface A-site cation segregation,nanoparticle sintering/agglomeration,surface decomposition caused by ion leaching in actual strong acid and strong alkaline electrolytes,as well as deactivation by adsorption and the poisoning by various contaminants in the reaction.These issues can result in unsatisfactory catalytic performance and are not conducive to the sustainable utilization of resources.To address these problems,the evolution processes of catalysts under different conditions were characterized and analyzed,and the corresponding activation strategies were proposed.The main research results are as follows:（1）A proton-assisted wet chemical leaching approach was proposed.Protonation can expand the perovskite oxide lattice,refine the surface grains,and increase the specific surface area of the perovskite.In addition,the acidic solution can selectively dissolve the inactive A-site ions segregated on the surface of perovskite,generating a spinel-perovskite heterointerface through surface reconstruction.Such heterogeneous configuration optimized the electronic structure of perovskite oxide that contributed to the excellent catalytic performance of 280 m V overpotential at 10 m A cm^-2 during the oxygen evolution reaction.This method is simple and easy to operate,and can be carried out at room temperature,providing a new way to solve the issues of inactive phase segregation and surface deactivation of catalysts.（2）The method of in situ exsolution was introduced to construct metal-oxide nano-heterostructures.The nanocomposites of Ni-Co bimetallic and Ba O based on Pr Ba Mn₂O₅double perovskite oxide were prepared successfully.The metal nanoparticles supported by this method,tightly"anchor"on the substrate,exhibiting strong anti-coking ability at high-temperature.In addition,the metallic nanoparticle on the surface can re-dissolve into and exsolve from the perovskite lattice by the oxidation-reduction cycle operation,realizing the activation and regeneration of the catalyst.By adjusting the proportion of defects and doping elements,controllable surface decomposition can be induced by the exsolution process.Ba O produced by the decomposition layer acted as a cocatalyst,improving the capacity of coking resistance and stability in the methane dry reforming reaction.On the other hand,through the characterization and exploration of the surface structure states of the material during the exsolution and catalytic reaction process,the room temperature aging phenomenon of Ba-based oxides was found.And this carbonation aging process,together with the X-ray diffraction structure refinement,can be used to analyze the thickness of the decomposed surface layer of the catalyst quantitatively.This quantitative analysis method provides a new perspective for breaking through the characterization limitation of catalyst decomposition at surface nanometer thickness.（3）A strategy of high-temperature sulfidation was proposed to solve the problem of agglomeration and poisoning caused deactivation of Ni-based catalysts under industrial conditions.By treating the deactivated Ni-based catalyst with 0.5%H₂S+H₂ at 850°C for 5minutes,a phase transition can occur to generate nickel sulfide polyphase.In this high-temperature environment,the Ni-S eutectic phase formed finely dispersed nickel sulfide complexes and many large open-pore structures,thus realizing the activation of the electrode.Thanks to the rich Ni-S multiphase composite structure,the activated catalyst exhibited good bifunctional oxygen catalysis and can be used as an air electrode catalyst in a self-assembled Zn-air battery device,exhibiting a power density of 165 m W cm^-2 and more than 100 h cycle charge-discharge stability.