Preparation And Performance Of CoMo And CoFe-based Phosphides For Overall Water Splitting

With the increase of energy consumption and environmental pollution,the development of new energy sources is imminent.Electrolyzed water is a promising way to solve the energy and environmental crisis,which can produce hydrogen energy with zero carbon dioxide emission.However,both hydrogen evolution and oxygen evolution require efficient catalysts.Metal organic frameworks（MOFs）have great potential in the field of electrocatalysis due to it’s large specific surface area and controllable pore structure.The Co-based electrocatalyst developed based on ZIF-67 further improves the catalysts performance of the material.In this paper,we use ZIF-67 as the preursor and doped different elements to improve the catalytic performance of the Co-based materials and explore it’s catalytic mechanism.The specific research contents are as follows:The hydrothermal method was used to dope Mo in the ZIF-67.By optimizing the experimental parameters,the Co-Mo-P/C/NF catalyst supported by foamed nickel is obtained after phosphating.The hydrogen evolution performance of the catalyst was evaluated by SEM,XRD,XPS and electrochemical testing methods.Because of the activation,the hydrogen evolution overpotential of the Co-Mo-P/C/NF catalyst decreases in both acidic and alkaline media.In the 0.5 mol/L H₂SO₄ solution,the elemental Co produced by activation can promote the adsorption and binding of active hydrogen atoms,so that the hydrogen evolution overpotential of the catalyst is 72 m V at a current density of 10 m A/cm².In the 1 mol/L KOH solution,theβ-Co（OH）₂ produced at the same time of activation further promotes the splitting of water molecules,making the hydrogen evolution overpotential of the activated Co-Mo-P/C/NF catalyst only 75 m V at 50 m A/cm^-2 current density.At the same time,the activated Co-Mo-P/C/NF catalyst showed excellent stability after 50 h constant potential test and 10000 CV cycles in acidic and alkaline media.Fe element was doped in the ZIF-67 at room temperature.By adjusting the experimental parameters,the Fe-Co-P/C/NF composite electrocatalyst with nano-sheet structure was synthesized after phosphating.Studies have shown that nano-sheet structure is conducive to the full exposure of active sites,and the synergy between Fe P and Co P makes Fe-Co-P/C/NF catalysts show excellent water electrolysis performance.In 1 mol/L KOH solution,to obtain the current density of 50 m A/cm² and 100 m A/cm²,the oxygen evolution overpotential of Fe-Co-P/C/NF is 270 m V and 282 m V,respectively.At the current density of 20 m A/cm²,the hydrogen evolution overpotential is 185 m V.Nevertheless,Fe-Co-P/C/NF showed excellent stability after 20 h constant potential test and 1000 CV cycles in alkaline media.