Synthesis Of Iron-based/cobalt-based Electrocatalysts For Water Splitting

In the industrial era,the sustained consumption of fossil fuels on a global scale has brought about serious energy crises and environmental issues.Therefore,developing renewable energy sources and gradually reducing dependence on fossil fuels is an urgent task.Hydrogen energy is considered one of the cleanest and most promising energy sources.Currently,Ru/Ir-based materials exhibit the best catalytic activity for the oxygen evolution reaction（OER）,while Pt metal has the optimal catalytic activity for the hydrogen evolution reaction（HER）.However,their scarcity and high cost hinder their large-scale application.Therefore,the development of efficient and low-cost electrocatalysts is important for promoting the large-scale application of hydrogen energy.The focus of this paper is to prepare Fe-based/Co-based catalysts with excellent catalytic performance and stability through a simple synthesis method.Firstly,a series of FeSe_x catalysts were synthesized via a solvothermal method using Fe（CO）₅ and Se powder as materials.A novel FeSe/FeSe₂ heterostructure catalyst was constructed by regulating the mole ratio of the reactants.Compared to FeSe and FeSe₂,the FeSe/FeSe₂ heterostructure exhibited better OER catalytic activity and faster reaction kinetics in 1.0 M KOH.The FeSe/FeSe₂ heterostructure only required an overpotential of 309 m V to provide a current density of 10 m A cm^-2 and the Tafel slope was 82.2 m V dec^-1 with good stability.Secondly,the OER activity of 434-L stainless steel in alkaline electrolyte was improved by a simple and feasible corrosion and sulfidation strategy.During the electrochemical process,the surface-generated Ni_xFe_1-xS acted as a pre-catalyst,with some S elements leaching out and rapidly reconstructing into S-doped Ni_xFe_1-xOOH with oxygen vacancies.The synergistic effect between the oxygen vacancies and different metals enabled the S-doped Ni_xFe_1-xOOH to achieve a current density of 10m A cm^-2 at a lower overpotential（298 m V）with a Tafel slope of 54.8 m V dec^-1,while also possessing a larger electrochemical active surface area.Finally,Co nanoparticles were encapsulated in Zn,N co-doped carbon nanotubes using a bimetallic oxide template.In 0.5 M H₂SO₄,Co@Zn-N-CNTs exhibited excellent HER performance,with an overpotential of only 67 m V at 10 m A cm^-2 and a Tafel slope of 50.23 m V dec^-1,while also showing long-term stability.Furthermore,Co@Zn-N-CNTs also demonstrated good HER catalytic activity in 1.0 M KOH(η₁₀=218 m V)and1.0 M phosphate buffer(η₁₀=132 m V).The outstanding HER activity of Co@Zn-N-CNTs is attributed to the synergistic effect between Co nanoparticles and Zn,N co-doped carbon nanotubes.