Study On Cobalt-based Carbon Nanocomposite Electrocatalysts For Water Electrolysis

Using electrolytic water technology to convert the electric energy generated by sustainable energy into hydrogen energy is an important link in the future renewable and clean energy structure.However,the water electrolysis technology still faces many challenges,such as low reaction efficiency,expensive electrode materials,poor stability and so on,which seriously restrict the large-scale development of electrolytic water technology and hydrogen energy.The key to solve these problems is to develop new electrocatalyst materials with low cost,high activity,high stability,and easy large-scale synthesis to replace the commonly used noble metal-based electrode materials.In this paper,combined with the advantages and characteristics of carbon-based nano materials and cobalt-based materials,composite electrocatalyst materials suitable for anodic oxygen evolution reaction(OER)and cathodic hydrogen evolution reaction(HER)in water electrolysis were synthesized and studied respectively.The morphology and catalytic activity were modulated by amorphization,sulfuration,monatomization and defect regulation.The main contents of this paper include the following parts:(1)Carbon nanotube supported amorphous Co O_xS_y electrocatalyst was obtained by combining the organic complex of cobalt with double wall carbon nanotubes and further vulcanization.The effects of amorphous phase and different level of sulfuration on the catalytic activity of the catalyst were studied.The catalyst has excellent intrinsic activity,large electrochemical active surface area and excellent stability,and exhibits an OER catalytic activity comparable to noble metal catalysts.(2)The cobalt single atom catalyst supported on carbon nano sheets was obtained by one-step pyrolysis after modification and nanosizing of chitin with phytic acid and cobalt ions by top-down method.The effects of different pyrolysis temperatures on the morphology,phase and structure of the materials were studied,and the carbon defects and single atom structure were characterized.The catalyst not only has ultra-high HER catalytic activity beyond Pt/C in alkaline environment at high current density,but also exhibits a good electrochemical stability.(3)The synthesized electrocatalyst materials were simulated and analyzed by using the first principle density functional theory(DFT)calculation,and their microstructure and catalytic active sites were discussed.Through the further calculation and analysis of the electronic structure of the catalytic materials,the source of their electrocatalytic activity and the effects of different kinds of carbon defects on their stability and catalytic activity were studied.In general,this work successfully prepared and deeply studied the efficient,cheap,and stable OER and HER electrocatalysts.More importantly,these catalysts have low raw material cost and easy preparation process,which are very suitable for large-scale promotion and application.The work of this paper will provide more ideas for the development and design of new composite electrocatalyst materials,as well as the further development of hydrogen energy and electrolytic water technology.