Preparation And Application Of High Performance Transition Metal Composite Catalysts In Electrocatalytic Oxygen Conversion Reaction

At present,human society faces with a serious fossil energy crisis and environmental pollution problems,which have threatened the sustainable development of human society.Therefore,reducing the use of fossil fuels,large-scale application of electrocatalytic energy conversion and electrochemical storage equipment are imperative.However,the performance of these devices is limited by the following electrochemical reaction kinetics:oxygen reduction reaction,hydrogen evolution reaction and oxygen evolution reaction,etc.Some noble metals,such as Pt,Ir and Ru are considered as efficient electrocatalysts,but their scarcity and high cost hinder large-scale application.Therefore,the design and preparation of highly efficient non-noble metal electrocatalysts have attracted great attention.In this paper,a series of cheap transition metal electrocatalysts were designed and prepared around the transition metal,and the activity of the materials in different types of electrocatalytic conversion reactions was improved through reasonable structural design.The main contents are as follows:（1）Phytic acid and melamine are used as phosphorus source and nitrogen source respectively,phytic acid has strong chelating properties and strong coordination ability for most metal ions.The nitrogen-doped iron phosphide nanoparticles（Fe P@N/C）was achieved through the equal volume impregnation method and a simple one-step pyrolysis strategy.Fe P@N/C exhibits higher oxygen reduction（ORR）catalytic activity in alkaline electrolytes,the Fe P@N/C calcined at 900°C has the best structure and catalytic performance,with an onset potential of0.98 V（vs.RHE）and a half-wave potential of 0.89 V（vs.RHE）,which are better than commercial precious metals Pt/C catalyst has better durability and anti-methanol interference ability than Pt/C catalyst.（2）Taking self-made Co-MOF as the precursor,introducing phosphomolybdic acid(PMo₁₂)into it,2-MIM as the carbon source,and calcining under high temperature conditions,the bimetallic carbide Co₆Mo₆C was obtained.Co-MOF/PMo₁₂-6-700 has good electrocatalytic oxygen evolution performance and good stability due to its large electrochemical active area and fast reaction kinetics.The current density reaches at 10 m A cm^-2,the required potential is only 1.539 V,which is better than many non-noble metal catalysts.（3）Using 2-methylimidazole as a ligand coordinated with Co²⁺,Zn²⁺and thiourea,a precursor material with a regular dodecahedron structure was obtained through hydrothermal,and then a heterostructure Zn S@Co₉S₈ composite material was prepared by calcination.By adjusting the temperature,it is finally determined that the Zn S@Co₉S₈ composite material calcined at 800°C has the most excellent ORR catalytic performance,with an initial potential of 0.98 V（vs.RHE）and a half-wave potential of 0.9 V（vs.RHE）.And the stability and methanol resistance are better than commercial Pt/C.