Application Of Transition Metal Oxides/hydroxides In Electrocatalytic Oxidation

With the rapid development of social economy,people’s demand for energy is increasing day by day.At the same time,with the continuous consumption of fossil energy,human beings are facing a more and more serious energy crisis.In addition,the pollution caused by the use of fossil energy cannot be ignored.Therefore,it has become a research hotspot in recent years to find sustainable new clean energy and solve the current energy and environmental problems.Among the many solutions,electrochemical technology has become a research hotspot in recent years due to its high efficiency and simple operation.Hydrogen energy has the characteristics of high combustion calorific value,clean and pollution-free,and is an ideal new clean energy.Electrochemical decomposition of water to produce hydrogen is one of the important methods for mass production of hydrogen.In the reactions of electrocatalytic water splitting,due to the four-electron transfer process,oxygen evolution reaction(OER)is very slow in kinetics and more difficult to occur than electrocatalytic hydrogen evolution reaction.Based on this,the high overpotential and high price of anodic catalytic materials are one of the limiting factors for the development of electrocatalytic water splitting.So,it is important to explore anodic catalytic materials for electrocatalytic oxygen evolution reaction(OER).At the same time,considering that the equilibrium potential of OER is 1.23 V vs RHE,the potential of urea oxidation(UOR)is only 0.37 V vs RHE.UOR is expected to partially replace OER in specific fields.For example,UOR-based urea fuel cells also have broad application prospects in terms of sustainable energy development.In addition,urea is widely present in human and animal urine and industrial wastewater,and is also the main pollutant in water.Electrocatalytic urea oxidation technology can be used to treat urea-rich sewage,and this process will not cause other pollution.In recent years,it has also received more and more attention in the field of environmental governance.Therefore,the development of electrocatalytic anode materials with high efficiency of decomposition of water,urea oxidation and other properties is of great significance to solve the existing energy and environmental problems.Compared with traditional catalysts based on noble metals,transition metal oxides/hydroxides are considered as potential substitutes for noble metal catalytic materials due to their abundant reserves and low price.However,this kind of materials usually have the disadvantages of high overpotential,low current density and slow kinetics,which restrict its further development and application.Therefore,how to further reduce its overpotential,increase its current density and improve its kinetic retardation is a key scientific problem in this field.In this paper,the electrocatalytic oxidation performance of transition metal oxides/hydroxides is further improved by means of three-dimensional structural design,the introduction of light energy and manufacturing defect sites and so on,further reducing its potential,improving the current density,and the overall catalytic efficiency has been increased.The mechanism of performance improvement has also been discussed deeply.The specific research contents are as follows:In the first chapter,electrocatalytic technology and its application prospect are systematically introduced.Common electrocatalytic oxidation reactions are introduced in detail.Common preparation methods of electrode materials,noble metals and non-precious metals based electrocatalytic materials and common strategies for improving performance are also described.Based on this,the methods,strategies,research contents and significance of this paper are presented.In chapter 2,based on the idea of three-dimensional structure design,Ni3S2/NiFe LDH with three-dimensional core-shell structure was obtained by hydrothermal method and electrodeposition method.And its crystal structure,microscopic morphology and electrochemical properties were characterized in detail.The experimental results show that the combination of the two can effectively improve the performance of the electrocatalytic OER,and the overpotential under the current density of 10 mA/cm2 increases by 30 mV.The special structure leads to the larger specific surface area and the exposure of more active sites,so that the material properties can be improved.In chapter 3,based on the idea of introducing light energy,the NiO nanosheets and the gold nanospheres were synthesized by hydrothermal method,calcining method and chemical reduction method respectively.The NiO@Au composite was obtained by combining the two materials through electrostatic interaction.And the crystal structure,microscopic morphology and electrochemical properties were tested in detail.It was found that the combination of gold and the introduction of light energy could greatly increase the number of NiⅢ active species,thus significantly enhancing the catalytic activity of electrocatalytic oxidation of urea.In chapter 4,Based on the idea of introducing defect sites,Zn was introduced into Ni(OH)2 nanosheets by a hydrothermal method.And the defective Ni(OH)2(D Ni-OH)was obtained by alkali corrosion.The electrochemical characterization and elemental analysis were carried out in detail.The experimental results showed that the surface Zn was successfully removed and the electrocatalytic oxidation performance of the material was significantly improved.In the fifth chapter,the research content of this paper is summarized and the feasibility of the strategy proposed in this paper is explained.The innovation of this paper is further summarized,the shortcomings of this paper are also been put forward,and the future work is forecasted.This paper use transition metal oxide/hydroxide as the research objects,from the solutions of three-dimensional structure design,the introduction of light energy and manufacturing of defect sites,having designed Ni3S2/NiFe LDH,NiO@Au and defect rich Ni(OH)2 for electrocatalytic oxidation reaction.The electrochemical performance tests show that the catalytic oxidation properties of various catalysts have obviously been improved and promoted.Related work also provides ideas and inspiration for the design and synthesis of other electrocatalytic materials with high-efficiency.