Preparation Of Carbon Foam Supported Co-based Self-supporting Electrode By Inkjet Printing And Electrocatalytic Water Splitting Performance

With the global fossil energy crisis and the worsening of ecological and environmental pollution,there is an urgent need to develop clean and sustainable new energy sources.The only combustion product of hydrogen energy is water,which is considered to be one of the cleanest and most promising renewable energy sources.A sustainable and environmentally friendly way to produce hydrogen is through electrocatalytic water splitting,which entails two half reactions:the hydrogen evolution reaction（Hydrogen Evolution Reaction,HER）and the oxygen evolution reaction（Oxygen Evolution Reaction,OER）.At present,precious metal Pt-based catalysts and Ru/Ir-based catalysts are the catalysts with the highest activity in hydrogen evolution and oxygen evolution respectively,but the low natural content and expensive price of precious metals prevent widespread practical applications.Transition metal based materials are expected to replace precious metal materials as electrocatalysts because of their rich content,low cost and high catalytic activity.Metal-organic frame materials（Metal-organic frameworks,MOFs）can be used to prepare precursors of composites with various properties because of their adjustable pores,easy to change composition,diverse morphological structures and high specific surface area,so that the derived materials of MOFs or MOFs have been widely studied and widely used in the field of catalysis.Therefore,cobalt-based self-supporting electrodes derived from carbon foam loaded with MOFs were prepared based on inkjet printing nanodeposition technology.The electrocatalytic activity of the materials was improved by means of selenide phosphating treatment,adjusting metal mass ratio,doping different metal species on 3D substrate carbon foam（Carbon foam,CMF）.The self-supporting electrode of carbon foam supported CoSe₂ nanoparticles（CoSe₂/CMF）was prepared by inkjet printing-carbonization-selenization,the impacts of selenization and phosphating on the hydrogen evolution and oxygen evolution characteristics of nanocatalysts,as well as the effects of various loading strategies on catalytic performance,were examined.Electrochemical tests show that CoSe₂/CMF shows good activity under alkaline conditions.When the current density reaches 10 m A·cm^-2,the hydrogen evolution electrochemical test results show that the overpotential of CoSe₂/CMF requires 122.6 m V,and the Tafel slope is 67m V·dec^-1,at the same time the OER test results showed that the overpotential of CoSe₂/CMF required 400.0 m V and the Tafel slope was 58 m V·dec^-1.Moreover,the catalytic performance of CoSe₂/CMF synthesized by inkjet printing nanodeposition technology is better than that of wet impregnation and dip coating,which proves the superiority of inkjet printing.The porous carbon foam supported Cosingle atom self-supporting electrode was prepared by inkjet printing-high-temperature pyrolysis-acid etching（Co-N/CMF）.By preparing the precursor MOFs and adjusting the mass ratio of Zn/Co,the effects of different mass ratios of Co-N/CMF catalysts on hydrogen evolution and oxygen evolution were investigated.The electrochemical test results show that Co-N/CMF-20 shows good catalytic activity,under acidic conditions,when the current density of 10 m A·cm^-2 is reached,the overpotential required for the HER reaction is only 41.3 m V,and the Tafel slope is 94 m V·dec^-1,the overpotentials required for HER and OER to provide a current density of 10 m A·cm^-2 under alkaline conditions are 59.6 m V and 390 m V,respectively,and the Tafel slope is 106 m V·dec^-1 and 80m V·dec^-1,respectively.The DFT theoretical calculation shows that the synergistic effect between adjacent single atoms formed by high single atom density in the catalyst produces favorable charge transfer and moderate binding with intermediates,thus improving the catalytic activity.The porous carbon foam loaded CoNi dual atom self-supporting electrode was prepared by inkjet printing-high-temperature pyrolysis,by doping different metal elements in MOFs,and the influence of CoNi dual atom catalyst materials on hydrogen evolution performance under acid and alkaline conditions was investigated.The electrochemical test results showed that the overpotentials required for CoNi-N/CMF to provide a current density of 10 m A·cm^-2 under acidic and alkaline conditions were 32.6 m V and 36.6 m V,and the Tafel slopes were 92 m V·dec^-1 and 102 m V·dec^-1,respectively.Combined with DFT theoretical calculation,the catalytic mechanism between diatoms in the catalyst was revealed,and the results showed that the synergy between Coand Ni atoms was generated by adjusting the electronic structure to improve the catalytic performance of the material.