Preparation Of Self-supporting Electrodes And Performance Study On Electrolysis Of Bunsen Reaction Products For Hydrogen Production

Concerned about energy scarcity and environmental degradation,researchers focus on the development of green and efficient hydrogen production.The sulfur-iodine（SI）cycle is relatively low cost and has the potential for large-scale hydrogen production by thermochemical water decomposition.Bunsen reaction is one step of the SI cycle and the products are H₂SO₄ and HI.The electrolysis of Bunsen reaction products is essentially the electrolysis of hydriodic acid to produce hydrogen and iodine.Recoverable elemental iodine with low solubility participates in the Bunsen reaction again,and the separated sulfuric acid solution participates in the sulfuric acid decomposition reaction.The method can avoid the direct separation of the products of the Bunsen reaction,which requires the participation of excess reactants and complex operations,thereby simplifying the SI cycle process and producing hydrogen efficiently.Transition metal sulfides have been extensively studied as novel electrocatalysts,featuring low energy bandgap,energy barrier,low price and easy availability,which has been widely concerned by researchers.The catalytic performance is improved by introducing heteroatoms into transition metal sulfides.In this paper,the following research results were achieved:（1）Carbon layer was successfully coated on the nickel foam substrate by the carbonization method with phenolic resin as the carbon source,and Ni₃S₂-C/nickel foam self-supported electrocatalytic electrode was prepared by hydrothermal method using carbon coated nickel foam as substrate and nickel source.The prepared Ni3S2-C/nickel foam self-supporting electrocatalytic electrode showed excellent catalytic performance for iodine evolution reaction,the current density of NF-800-0.73-24electrocatalytic electrode was 1.451 A cm^-2 at the potential of 1.0 V,Tafel slope was195.4 m V dec^-1,the Faradaic efficiency was 95%.Unmodified nickel foam had poor acid resistance.Doping of sulfur and carbon,the synergistic effect of not only improved the corrosion resistance of Ni₃S₂-C/nickel foam electrode but also improved its electrocatalytic activity.（2）The NiCo₂S₄@carbon cloth self-supporting electrocatalytic electrode was prepared on a carbon cloth substrate using a simple one-step hydrothermal method with superior catalytic performance compared to monometallic sulfides modified electrode.A series of Ni-Co-S@CC composite electrode materials were prepared by adjusting the ratio of Ni and Co addition.The Ni-Co-S@CC（1:2）electrocatalytic electrode exhibited a current density of 1.670 A cm^-2 at 1.0 V,which was 371 m A cm^-2 higher than that of the pure carbon cloth,which was 3 times higher than that of Pt electrode,the current density of continuous 20 h constant potential measurement was basically constant.The synergistic effect and variable valence state of cobalt element and nickel element were favorable to improve the catalytic activity.（3）The Ni-P-S@carbon cloth self-supporting electrocatalytic electrode was prepared by a simple and mild one-step electrodeposition method,using sodium hypophosphite as the phosphorus source and thiourea as the sulfur source.At 1.0 V,the current density of the Ni_0.2P_0.5S_1.0@CC electrocatalytic electrode can reach 1.721 A cm^-2,only decreased by 36 m A cm^-2 after 1000 CV cycles measurement,and the Faraday efficiency was 97%in 60 min constant current polarization measurements.It has been shown that modification of Ni-P-S composites on carbon fibers could improve the IER catalytic activity.