The Controllable Synthesis Of Nickel-Based Electrocatalysts And The Performance Of High-Current Electrolysis In Seawater

The serious environmental pollution and energy shortage caused by the extensive use of fossil fuels have become increasingly severe problems.In the context of“carbon peak”and“carbon neutrality”,it is necessary to protect non-renewable resources immediately,develop renewable energy,and promote sustainable development.Hydrogen（H₂）has the advantages of high energy density and zero carbon emissions,making it one of the most attractive green energy sources.Among many hydrogen production methods,electrolysis of water is a green conversion process that has attracted a lot of attention.Currently,most electrolysis water systems use pure water as the electrolyte,while seawater,which accounts for97%of the Earth’s water resources,has not been fully developed and utilized.Compared with pure water,seawater not only has economic advantages but can also be used to desalinate seawater and solve water shortages in arid areas.In recent years,electrolytic seawater electrocatalysts have been widely studied,and improving the activity of the hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）at the cathode and avoiding the anodic chloro-oxygen reaction（Cl OR）under alkaline conditions are currently the core issues to be solved for electrolytic seawater catalysts.Nickel-based materials are ideal electrolytic seawater catalytic materials because of their abundant resources,low cost,and adjustable electronic structure.However,their activity still needs to be improved.In addition,most reported electrocatalysts can only withstand lower current densities(<100 m A cm^-2),severely limiting the industrialization process of electrolytic seawater.Therefore,the reasonable design and targeted synthesis of Ni-based electrolytic seawater electrocatalysts with high activity and high current endurance have become a top priority.The main research contents are as follows:（1）Electrocatalysts need to have excellent activity and long-term stability under industrial ampere-level current density electrolysis of seawater.Fe,S co-doped Ni（OH）₂nanosheet arrays with oxygen vacancies（Fe,S-Ni（OH）₂-Ov）were prepared by a rapid liquid-phase synthesis method at room temperature.Fe,S-Ni（OH）₂-Ov electrocatalysts can not only be synthesised rapidly,but can also be prepared in large sizes,which provides the prerequisites for industrial production.Moreover,Fe,S-Ni（OH）₂-Ov exhibited good OER performance in alkaline seawater,reaching1000 m A cm^-2with only 340 m V overpotential.Under simulated industrial seawater conditions,Fe,S-Ni（OH）₂-Ov|Pt/C only needs 1.65 V to achieve 1000 m A cm^-2.In situ EIS confirms that oxygen vacancies enable faster adsorption kinetics of intermediates（OH*）in the OER process,further demonstrating that oxygen vacancies allow rapid adsorption of OH*intermediates at low potentials,facilitating the OER process and effectively improving the catalytic performance of the catalyst.This strategy provides a feasible way for the application of catalysts in industrial production,and has important significance in seawater electrolysis.（2）Considering that the hydrazine oxidation reaction（HzOR）has a much lower thermodynamic potential,hydrazine oxidation assisted electrolysis of seawater is an effective strategy to prevent chloride oxidation reactions and to achieve energy efficient hydrogen production.Fe,F co-doped Ni₂P heterostructure nanosheet arrays（Fe/F-Ni₂P@NC）with a unique 2D/3D structure were constructed on nickel foam.The array exhibited excellent Hz OR and HER performance in alkaline seawater,reaching 1000 m A cm^-2with only 122 and 323 m V potential,respectively.DFT results showed that the co-doping of Fe and F realized electron redistribution and optimized the electronic structure.Moreover,compared with the OWS seawater system,the OHz S dual-electrode system only requires 571 m V of cell voltage to achieve 1000 m A cm^-2,saving 3.35 k W·h for producing 1.0 m³H₂.In addition,the use of industrial hydrazine effluent as a feedstock for the electrolysis system rapidly degrades the hydrazine hydrate effluent to～5 ppb.By combining small molecule oxidation with electrolysis of seawater,the reaction overpotential is further reduced,the corrosion of the catalyst and electrodes by Cl O^-is reduced and stability is improved.It exploits a new avenue for energy-efficient hydrogen production.