Fabrication Of Co-based MOFs Derived Hollow Structured Electrocatalysts For Hydrogen Production

Hydrogen（H₂）is considered as an ideal substitute for fossil energy due to its high energy density and green environmental protection.Hydrogen production by electrolytic water driven by green electricity is an ideal hydrogen production method.High activity catalysts are needed for efficient water electrolysis to produce hydrogen to reduce the reaction overpotential and preparation cost.Platinum（Pt）-based catalysts have excellent catalytic activity for hydrogen evolution reaction（HER）,but the high cost and scarcity of Pt limit its commercial application.Transition metal cobalt（Co）has abundant resources and low price,and Co-based catalyst has better HER electrocatalytic performance,but there is still a certain gap compared with Pt,which requires further optimization and regulation for electronic structure and morphology design.Metal-organic framework materials（MOFs）are ideal precursors for high-activity Co-based catalysts due to their high porosity,large specific surface area and designability of composition/structure.Based on the above considerations,in this paper,Co-based MOFs material as a precursor system to prepare efficient Co phosphide and selenide catalyst,through the morphology control,crystal control,heteroatomic doping and other means to design and optimize the catalytic performance of Co based catalysts,the research content is summarized as follows:（1）PA assisted synthesis of lamellar porous hollow Co₂P@C electrocatalyst.Phytic acid（PA）was used to etch ZIF-L,a co-based MOFs material,to prepare the hollow precursor,and phosphorus source was introduced to construct the hollow structure.In the subsequent calcination process,Co₂P nanoparticles were formed by in-situ phosphating of the precursor,and uniformly distributed on the surface of the carbon support,resulting in a catalyst with unique leaf-shaped porous hollow structure Co₂P@C.The porous hollow Co₂P@C showed good HER performance and catalytic stability in both acidic and alkaline electrolyte,and the current density of 10 m A cm^-2 could be reached by overpotential of only 127 m V and 157 m V.In this work,the etching process and transformation mechanism of PA are systematically analyzed.The PA assisted phosphating synthesis method can be widely used in the design and preparation of other hollow structure TMPs@C materials.（2）Synthesis of cubic phase Co Se₂（c-Co Se₂）electrocatalyst induced by Ru doping.Ru-doped c-Co Se₂（Ru-c-Co Se₂/CC）was prepared by means of Ru³⁺ion exchange reaction and selenization by in-situ growth of ZIF-L on conductive carbon cloth.At the same selenization temperature,the selenated product without Ru doping is the ortho-intersection phase Co Se₂（o-Co Se₂）.In this work,the influence of Ru doping amount and selenization temperature on the morphology and composition of catalyst was investigated,and the transformation mechanism of Co Se₂ induced by Ru was further revealed,and the structure-activity relationship between catalyst structure and hydrogen evolution performance was studied.In addition,the hydrophobic properties of sheet array structures were studied,and the mechanism of hydrophobic structures on improving electrocatalytic performance is revealed.The best catalyst Ru-c-Co Se₂/CC has excellent HER electrocatalytic performance in acidic and alkaline electrolyte,and only needs 135 and186 m V overpotential when reaching 100 m A cm^-2 current density,respectively.