Design,Synthesis And Studies Of Cobalt-Based Non-precious Metal Materials For Electrocatalytic Water Oxidation

There is still an ongoing effort to search for sustainable,clean and highly efficient energy generation to satisfy the energy needs of modern society.Hydrogen energy is the future star in the energy field due to its wide range of sources,high combustion calorific value,clean,pollution-free,abundant forms of use,convenient energy storage,and good safety performance,and it is also called‘ultimate energy'by industry experts.Hydrolysis of hydrogen realizes the conversion between electrical energy and chemical energy,and it is not accompanied with the generation of pollutants when releasing energy.Therefore,it is considered as one of the best feasible solutions for hydrogen generation by scientists.The kinetics of water oxidation is very slow,involving complex four-proton and four-electron transfer processes and still a bottleneck in hydrogen production from electrolyzed water.Many early studies focused on the development of iridium and ruthenium oxides as water oxidation catalysts,but the high cost and scarcity of precious metals has limited their large-scale applications.At present,many studies have focused on the development of various non-precious metal catalysts which are inexpensive,efficient and stable.The dissertation summarizes the research progress of electrocatalytic water oxidation and the application of a variety of catalyst materials in the field of water oxidation.And we designed and synthesized a variety of cobalt-based non-precious metal catalytic materials,and have been studied their structure,composition and catalytic performance.The main research contents are as follows:1.The Co-MOF complexes were successfully synthesized by a simple stirring method,and Co₃O₄ nanomaterials were synthesized successfully by using the Co-MOF as a sacrificial template.It was found that the Co₃O₄ nanocatalyst obtained at 350°C had the best catalytic activity.And the overpotential of 10 mA/cm²was 420 mV and the Tafel slope was 55mV/dec.2.A new type of Co₃O₄/Co?OH?₂ hybrid material was synthesized by a simple one-pot hydrothermal method,showing a strong interaction effect as a highly efficient electrocatalytic water oxidation catalyst.The overpotential of 10 mA/cm²is 373 m V and the Tafel slope is103 mV/dec.3.The ACo₂O₄/NF?A=Mn,Zn,Ni?composites were synthesized by hydrothermal method and calcination method directly as electrode materials.In this chapter,self-supporting electrodes made of nickel foam were introduced,and the influence on catalytic activity of doping different metal ions in ACo₂O₄/NF was investigated.We have obtained an order of OER performance:NiCo₂O₄/NF>MnCo₂O₄/NF>ZnCo₂O₄/NF,where Ni Co₂O₄/NF exhibits a small overpotential of 271 mV at 10 mA/cm² in a 1 M KOH solution.