Design And Synthesis Of Catalysts For Water Splitting And Their Electrocatalytic Performances

With the rapid development of global industry and the continuous progress of social economy,energy has an indispensable position.However,the continued dependence on non-renewable fossil energy will not only lead to energy shortage,but also the ensuing environmental pollution problem will become more and more serious.Humans realized that clean energy must be vigorously developed in order to achieve sustainable social development.Among them,hydrogen energy is recognized as the most potential energy carrier due to its high energy density and environmental friendliness,and electrolysis of water is an important means to obtain high-purity hydrogen.In addition to the hydrogen evolution reaction（HER）at the cathode,water electrolysis also includes the oxygen evolution reaction（OER）at the anode.The slow progress of the two processes leads to the problems of large overpotential and low energy conversion efficiency in water electrolysis cells.Therefore,it is very significant to develop efficient catalysts to speed up the reaction process,reduce the overpotential and energy consumption.At present,the conventional HER and OER catalysts are commercial Pt/C and Ru/Ir-based catalysts,respectively,but their scarce reserves and high prices will inevitably increase the cost and limit their further applications.Based on the above discussion,this thesis conducts experiments on how to reduce the amount of noble metals,reduce costs,and develop non-noble metal catalysts.The electrocatalytic performance can be improved by adjusting the morphology,crystal structure,atomic ratio and electronic structure of the catalytic material.Mainly done three parts of the work,the content is as follows:1.The Ir/CeO₂ nanorod catalyst was synthesized by a one-step hydrothermal method,which was used for efficient water splitting in an alkaline environment.The addition of CeO₂ reduced the content of Ir and improved the catalytic activity of Ir,and the high catalytic activity of Ir/CeO₂was mainly attributed to its intrinsic properties.Specifically,Ir/CeO₂ nanorods have an overpotential of 36 m V for HER at a current density of 10 m A cm^-2,which is 19 m V lower than that of commercial Pt/C;and 300 m V for OER,which is lower than that of benchmarked Ru O₂and Ir O₂ catalysts.Meanwhile,Ir/CeO₂ performs excellent stability and durability in both HER and OER.2.V-doped Co（PO₃）₂ micron rods were prepared on the nickel foam by dipping method and phosphating process,which were used for water splitting reaction under alkaline conditions.Among them,the introduction of V further optimizes the electronic structure of the material,making the specific surface area of microrods larger,which is more conducive to the water splitting reaction.Therefore,for HER,CoV（PO₃）₂/NF only needs a low overpotential of 97.5 m V in 1.0 M KOH solution to reach a current density of 10 m A cm^-2 with a small Tafel slope(84.8 m V dec^-1)and good stability;in terms of OER,in the same solution at the current density is 100 m A cm^-2,the overpotential and Tafel slope of the material are 368 m V and 21.3 m V dec^-1,respectively,which are better than other catalysts in the same series.3.SnSe₂ was synthesized on nickel foam substrate by a solvothermal method,and its HER catalytic reaction in alkaline medium was investigated.The atomic ratio of Sn and Se was changed,and the structural characterization proved that SnSe₂/NF has a larger specific surface area,which is more favorable for the HER reaction.The electrocatalytic test results show that SnSe₂/NF has an overpotential of only 26 m V at a current density of 10 m A cm^-2,which is superior to the commercial Pt/C catalysts.