Design And Preparation Of High Efficiency Hydrogen Evolution Catalysts For Seawater Electrolysis And Basic Research In Application Of Magnesium/seawater Batteries

As a green,clean,renewable energy source,hydrogen energy has a significant position in the field of new energy due to its high energy density,environmental friendliness,and only water as the combustion product.Electrolysis of water is an effective strategy for sustainable production of renewable energy hydrogen.However,current research on water electrolysis mainly relies on highly purified fresh water,resulting in significant economic and human costs in practical applications.With the increasing scarcity of freshwater resources,the research on electrolysis of seawater is more attractive.In addition,the hydrogen evolution cathode in the seawater environment can be coupled to a magnesium anode to form a Magnesium/seawater battery,which can not only generate electricity,but also produce hydrogen.This has significant practical significance for the power and hydrogen source supply of equipment and facilities in deep and distant seas.Herein,this article aims to design and synthesize high-efficiency catalysts for hydrogen evolution reaction（HER）in seawater and explore their application feasibility in Magnesium/seawater batteries.The main research contents are as follows:A series of tungsten bronze（A_xWO₃,A=Na,K,Rb,Cs,0<x<1）catalysts are designed and synthesized through a simple solvothermal process.Their electrocatalytic performance for seawater splitting and their applications in Magnesium/seawater batteries were investigated.The results show that tungsten bronze containing different alkali metals exhibits better HER activity than pure WO₃,among which Na_xWO₃deliveries the best performance with overpotential of only 108 and 111 m V at 10 m A cm^-2 in 1 M KOH and alkaline seawater,respectively.It can continuously produce hydrogen for more than 24 hours in alkaline freshwater and alkaline seawater,with no significant degradation in performance.When using Na_xWO₃ as a hydrogen evolution cathode of Magnesium/seawater battery,the as-assembled Magnesium/seawater battery achieves a peak power density of 5.05 m W cm^-2 and exhibits a good discharge stability of 24 hours under fixed current density of 3 m A cm^-2.At the same time,a Na_xWO₃-based Magnesium/seawater battery pack can successfully illuminate commercial LED panels,indicating its high potential in practical application.In order to promote electron transfer and dissociation of water molecules in seawater electrolysis,and to improve the HER activity and the performance of Magnesium/seawater batteries,a Ni/V₂O₃ Schottky electrode is designed and constructed by a simple hydrothermal method.It is found that metal Ni and semiconductor V₂O₃ can form an internal electric field in the form of Schottky junctions at the interface,which significantly promotes charge transfer and water dissociation.The resulting Ni/V₂O₃ Schottky electrode reveal a overpotential of only176 and 649 m V at current density of 10 and 1000 m A cm^-2,respectively.Magnesium/seawater batteries constructed with Ni/V₂O₃ Schottky electrodes exhibit a peak power density of up to 17.81 m W cm^-2 and excellent discharge stability for 24hours.Finally,a self-powered seawater electrolysis system driven by the as-fabricated Magnesium/seawater batteries can obtain a high hydrogen production rate of 12.42 m L cm^-2h^-1 from natural seawater without connecting to an external power grid,and the total energy conversion efficiency is as high as 80.87%,thus laying a theoretical and technical foundation for the energy supply of far-reaching offshore facilities and equipment.