The Investigation Of Oxygen Evolution Reaction Enhancement By Photothermal Effect Over Cobalt-Nickel-Carbide

Hydrogen is considered to be one of the cleanest energy sources,and the combustion product water can be recycled to produce hydrogen.Electrochemical decomposition of water to produce hydrogen has many advantages,and can use the nature of solar energy,wind energy and other renewable energy to achieve hydrogen and oxygen production.In the process of water electrolysis,oxygen evolution reaction（OER）is a slow half reaction in the total reaction of water decomposition,which greatly limits the efficiency of hydrogen preparation.Studies have shown that cheap and abundant transition metal element cobalt-based materials exhibit excellent OER performance,and the catalytic efficiency can be significantly improved by doping nickel and photothermal effects.In this paper,the mechanism of enhanced oxygen evolution performance of cobalt-nickel-carbide catalyst under solar irradiation was discussed mainly from the physical and chemical perspectives.Therefore,the following researches were carried out in this paper:1.A series of(Ni_xCo_1-x)₃C alloy particle OER catalysts were synthesized by ball milling from metallic elemental cobalt,nickel,and multi-walled carbon nanotubes.The test results showed that(Ni_xCo_1-x)₃C particles were of standard Co₃C crystal structure and had no other impurities,indicating that the crystal purity of Co₃C based catalyst synthesized by ball grinding was relatively high,and the material prepared by this method achieves the desired effect.2.(Ni_xCo_1-x)₃C were supported on hydrophilic carbon paper,and OER performance under photothermal assisted action was tested with simulated sunlight as the light source.Among these catalysts,(Ni_0.2Co_0.8)₃C can drive the current density of 10 m A cm^-2 with an over potential of 262 m V under the condition of simulated solar light source,and this result is superior to the oxygen evolution performance of most cobalt-based carbides.3.Furthermore,the influence factors of catalytic activity of(Ni_xCo_1-x)₃C under photothermal conditions were analyzed to explore the adsorption of cobalt site in the process of oxygen evolution and the sensitivity of light.In addition to accelerating charge transfer ability and reducing reaction kinetic barrier,interfacial photothermal effect can also stimulate the carrier in(Ni_xCo_1-x)₃C to participate in the reaction and accelerate the OH^-supplementing process in solution,thus enhancing the activity of OER.In addition,with the increase of the specific gravity of nickel added,the total number of excited carriers increased significantly,and the doped nickel promoted the transition of cobalt center from low to high state by adjusting the electronic environment of cobalt center.In summary,through in-depth exploration of the photoelectric response of(Ni_xCo_1-x)₃C catalyst and the causes of photochemical changes,this subject has reached the conclusion that Co is the photosensitive center of(Ni_xCo_1-x)₃C and can promote the adsorption effect of OH^-at the interface.It provides a feasible research scheme for high performance transition metal catalyst with high solar energy efficiency.