Construction And Electrocatalytic Performance Investigation Of Highly Efficient Supported Catalysts Based On Surface/Interface Structure Modulation

Energy crisis and environmental pollution are one of the hot issues that the world is concerned about at present.The development of renewable clean energy or technology is an effective way to solve the energy crisis.Among them,in green renewable energy storage and conversion technologies such as hydrogen production from water electrolysis and metal-air batteries,various electrode reactions have high energy barriers and slow kinetic reactions,resulting in low power output and energy utilization,such as hydrogen evolution,oxygen evolution and oxygen reduction reactions.Therefore,it is urgent to develop catalyst materials with abundant earth resources,low cost,high activity and good stability.Supported catalysts have been widely studied by researchers due to their unique advantages such as increasing the exposure of active sites,reducing the amount of active metals to reduce costs,and adjusting the size and local electronic structure of active metals.However,how to select a suitable support material and perform morphology control and surface modification,how to design a simple and feasible method to maintain high stability and high dispersibility of active particles,and how to realize the multifunctionalization of catalytic materials to improve their application value are the key scientific problem and difficulty that still needs to be solved urgently in the current electrocatalysis research.In this dissertation,several supported electrocatalysts with high activity,high stability and low cost were prepared based on the surface/interface control strategy（size,defect,interfaceand strain effects）.And the"structure-activity relationship"between the nanostructure and the electrocatalytic activity of the catalyst were further systematically studied,which is helpful for in-depth theoretical research on supported electrocatalysts and provides scientific guidance for further promoting its future commercial application.The main research contents and results are as follows:1.Based on the noble metal-like properties of transition metal carbides,guided by theoretical calculations,using cheap and resource-rich Mo₂C as a carrier,a simple solvothermal reduction method was used to prepare ultrathin atomic layer Pt clusters firmly anchored in N-Mo₂C nanorod-supported HER electrocatalyst（Pt/N-Mo₂C）,the prepared Pt/N-Mo₂C catalyst exhibits high activity and high stability for HER electrocatalytic performance at all p H values.The calculation results show that the ultrathin layer of Pt clusters on Mo₂C supports produces the lowestΔG_H*value.In addition,the experimental results show that the atomic-layer Pt clusters anchored on the Mo₂C support greatly increase the electron/mass transport efficiency and structural stability.At a current density of 10 m A cm^-2,its overpotential is only 8.3 m V,and it has an excellent long-term operating tolerance of more than 120 h.This research is expected to realize the universal preparation of large-scale high-capacity atomically dispersed noble metal catalysts and commercial applications.2.Based on the defect effect,using oxygen vacancy-rich molybdenum dioxide（Mo O₂）as a carrier,Pt single atoms（Pt SAs）were anchored in the oxygen vacancy(O_vac)defects of Mo O₂to prepare an atomically dispersed noble metal Pt SAs/Mo O₂supported HER electrocatalyst.The experimental and theoretical calculation results show that the oxygen vacancies provided by the Mo O₂NRs carrier can not only effectively stabilize the Pt single atoms,but also adjust the electronic structure of the active site（Pt）,enabling the Pt SAs/Mo O₂to perform excellent HER activity at full p H and high current density.Among them,the 1.1 wt%Pt SAs/Mo O₂NRs catalyst exhibited a long-term operational stability of 200 h at a large current density of-1000 m A cm^-2required for industrialization,and provided excellent HER mass activity(69.5 A/mg _Pt);compared with the benchmark 20wt%Pt/C commercial catalyst,its mass activity was improved by 28 times.Under the same activity condition,the price of 1.1 wt%Pt SAs/Mo O₂NRs catalyst is only 3.5%,1.76%and 3.1%of that of commercial 20 wt%Pt/C catalyst.3.Based on the control effect of interface engineering,an excellent supported ORR electrocatalyst Mo₂C/Fe₅C₂@NC was developed by a simple solid-phase method.Mo₂C/Fe₅C₂heterostructured nanoparticles with abundant interfaces were highly dispersed and supported on nitrogen-doped carbon（NC）supports.The experimental results show that the Mo₂C/Fe₅C₂@NC catalyst has efficient and stable ORR catalytic performance with an onset potential of 0.92 V and a large limiting current density(5.3 m A cm^-2at 0.1 V vs RHE),Compared with the doped Pt/C catalyst,it has stronger methanol tolerance and outstanding stability（40000 s）.This outstanding catalytic activity originates not only from the increased number of catalyst accessible active sites provided by the support and the high electrical conductivity of the NC support,but also from the adequate exposure of the Mo₂C and Fe₅C₂heterointerfaces.Such experimental design ideas expand the general synthesis of various metal carbide-based heterostructured nanomaterials.4.Based on surface strain engineering,we developed an excellent supported trifunctional electrocatalyst Ru/Ru O₂@NCS.Lattice mismatch strained core/shell Ru/Ru O₂nanoparticles are highly dispersed and supported on nitrogen-doped carbon nanosheets（NCS）.The experimental results show that,the in situ heteroepitaxial growth of Ru O₂shell on the stretchable Ru core results in lattice mismatch strain.The compressive strain-activated Ru O₂simultaneously enhances the OER,ORR,and HER activities of Ru/Ru O₂@NCS electrocatalysts,which provides a platform to elucidate the role of compressive strain in activating the multifunctional activity of the catalyst（Ru O₂）.When the Ru/Ru O₂@NCS catalyst was used in a rechargeable Zn-air battery,it achieved a power density of 137.1 m W cm^-2and an energy density of 714.9 Wh kg _Zn^-1.Furthermore,the fabricated Zn-air battery can drive a water splitting electrolyzer assembled by Ru/Ru O₂@NCS catalyst,which can reach a current density of 10 m A cm^-2with only a bias voltage of 1.51 V.Theoretical calculations indicate that the enhanced electrocatalytic performance stems from the compressively strained Ru O₂shell,which lowers the reaction barrier and enhances the binding strength of rate-determining intermediates（*H,*O,*OOH）,resulting in excellent OER/ORR/HER catalytic activity and stability.This study not only sheds new light on the elucidation of the structure-activity relationship between strain-adsorption-reactivity,but also provides a new idea for the rational design and development of multifunctional electrocatalysts for various energy conversion devices.