Design And Performance Study Of The Non-noble Metal Bifunctional Overall Water Splitting Electrode Based On Three Dimensional Porous Support

Electrolytic water hydrogen production technology coupled with new energy sources is an ideal way of energy conversion and storage.However,due to the slow kinetics of oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）,Large-scale electrolytic hydrogen production is still highly inhibited.Therefore,the development of efficient,stable and economical catalysts for reducing OER and HER energy barrier is the key to improve energy conversion efficiency,and has received extensive international attention.Three-dimensional transition metal phosphates,especially cobalt phosphates（commonly referred to as Co-Pi）,are considered as potential alternatives to precious metal based electrocatalysts due to their low cost,good stability and adjustable REDOX properties.In this paper,a kind of cobalt phosphate（Co₃（PO₄）₂4H₂O）tetrahydrate with Hopeite structure has been prepared by hydrothermal method using porous nickel foam as the base material and NiCo-LDH material as the intermediate layer by electrodeposition material as a catalytic layer of multi-layer structure self-supporting electrode（Co-H/NiCo@NF）preparation method,the main research content is as follows（1）The sandwich type catalyst was constructed by layer-by-layer assembly method.Firstly,a NiCo-LDH intermediate layer was prepared on nickel foam material by electrodeposition,and then a cobalt phosphate tehydrate catalyzed layer with Hopeite structure（Co-Hoepite layer for short）was prepared on NiCo-LDH intermediate layer by hydrothermal reaction.The growth of the Co-Hoepite layer on the NiCo-LDH layered double hydroxides（LDH）shows a unique sea urch-like morphology and a strong interaction between the catalytic layer and the mesosphere,resulting in excellent activity and stability.The results of electrochemical tests show that the Co-H/NiCo@NF overpotential of 180 m V and 350 m V can provide a current density of 100 m A cm^-2for HER and OER,respectively,while only 1.76 V device voltage is required to provide the same current density(100 m A cm^-2)in full hydrolysis.In addition,at the current density of 500 m A cm^-2,which is close to the industrial level,it can be stable for a long time and shows a tendency of increasing activity,which may be related to the formation of new phases and strong interlayer bonding.（2）By examining the results of the previous section,we found that in the"sea urchin"structure,the excessively long needle-like structure（more than 20μm in length）leads to a larger moment arm,which eventually leads to the fracture and detachment of the structure due to strong gas reaction during the mass transport at high current density,and leads to the degradation of the electrochemical activity of the catalyst at the early stage of the electrochemical test.In order to improve the performance of Co-H/NiCo@NF catalyst,in this part of the study,we are committed to regulating the surface structure morphology of the catalyst,optimizing the growth uniformity of the catalytic layer,so as to improve the catalytic activity and enhance the stability.In the experimental study,by adding different amount of PVP in the preparation of Co-Hopeite catalytic layer by hydrothermal reaction,the catalytic layer can be more uniformly formed on the surface of nickel foam,and the surface morphology and structure of the catalyst can be effectively regulated.The SEM results showed that the surface morphology of the catalyst changed greatly,and the SEM after the stability test showed that PVP（polyvinyl pyrrolidone,PVP）could help the surface morphology of the catalyst to better retain in the high current density test.This resulted in better OER activity and full hydrolytic activity,and demonstrated greater stability over 200,000 seconds in stability tests at 500 m A cm^-2current densities.