The Research On Preparation And Water Splitting Performance Of Transition Metal Oxide And Their Composites

The development of human society and energy are inseparable.Along with the consumption of traditional energy and the environmental pollution problems it brings,it is urgent to seek new energy to replace the dependence on traditional energy.Hydrogen has the characteristics of high efficiency,no pollution,and high energy density,and has been identified as a potential candidate for future energy.Electrolyzed water is an important way to obtain hydrogen.At present,in industrial applications,electrolyzed water mainly faces the high overpotential of the cathode and anode of the electrolytic cell,which causes high energy consumption and low efficiency of the electrolyzed water.Materials are of great significance to reduce the overpotential during electrocatalytic water decomposition.The catalytic activity of electrode materials is mainly affected by geometric and energy factors.Therefore,based on these two factors,this article designs and prepares transition metal oxides and their composites based on the methods of dealloying,annealing and hydrothermal synthesis,in order to obtain Electrode material with high catalytic activity and good stability,in order to reduce the overpotential in the process of electrolyzing water,and at the same time provide a reference for the design and preparation of composite electrode materials.Transition metal oxides are widely used in electrocatalytic water decomposition studies due to their simple preparation methods,low cost,and rich redox reactions.In this paper,spinel-structured AB₂O₄ type bimetal oxides NiFe₂O₄,NiCo₂O₄,and CoFe₂O₄ were prepared by rapid solidification combined with de-alloying and annealing treatment.XRD,SEM,TEM,XPS,etc.were used to analyze the electrode's phase,microstructure and surface chemical composition,as well as the element binding state,and linear scanning voltammetry,Tafel slope,AC impedance,cyclic voltammetry and constant current electrolysis Methods The electrocatalytic water-splitting performance of porous electrodes was tested.The results show that CoFe₂O₄ has the best electrocatalytic activity.At 50 mA·cm^-2 current density,the hydrogen evolution overpotential is 216 mV,the Tafel slope is 111.84 mV·dec^-1,the oxygen evolution overpotential is 351 mV,and the Tafel slope is 82.06 mV·dec^-1.At the same time,it has the highest exchange current density and the lowest apparent activation energy,indicating that it has high catalytic efficiency.Using it as both the cathode and anode materials for electrolyzed water,only 1.58 V is required to obtain a current density of 10 mA·cm^-2.At the same time,continuous electrolysis at a current density of 10 mA·cm^-2 for 12 h,no significant attenuation in voltage,Showing good electrocatalytic performance and excellent stability.At the same time,ABO₄ type bimetal oxides also have good electrocatalytic performance.Therefore,ABO₄ type bimetal oxides NiMoO₄ and CoMoO₄ were prepared by rapid solidification combined with de-alloying and annealing treatment.Compared with CoFe₂O₄,CoFe₂O₄ has electrocatalytic performance With higher catalytic activity,the CoFe₂O₄/NiMoO₄ and CoFe₂O₄/CoMoO₄ composite electrode materials with CoFe₂O₄ as the matrix were designed and prepared through hydrothermal synthesis and annealing treatment.SEM and TEM showed that NiMoO₄and CoMoO₄ adhered to the CoFe₂O₄ skeleton structure in a sheet structure.Their electrocatalytic performance showed that CoFe₂O₄/CoMoO₄ had the best electrocatalytic activity.At a current density of 50 mA·cm^-2,the hydrogen evolution overpotential was 193 mV,the Tafel slope is 100.44 mV·dec^-1,the oxygen evolution overpotential is 319 mV,the Tafel slope is 70.47 mV·dec^-1,and the overall water decomposition requires only 1.55 V to obtain a current of 10 mA·cm^-2 density,while continuously electrolyzing at a current density of 10 mA·cm^-2 for 12 h,the voltage changed only 11 mV,showing good electrocatalytic performance and stability.On this basis,CoFe₂O₄/CoMoO₄/rGO composite electrode material was obtained by further reducing and reducing graphene oxide?rGO?by hydrothermal method.XRD and Raman tests confirmed the existence of rGO.SEM and TEM showed that rGO adhered to CoFe₂O₄/CoMoO₄ framework has good compatibility with the matrix.Electrocatalytic tests showed that the hydrogen evolution overpotential was 172 mV,the Tafel slope was 99.36 mV·dec^-1,the oxygen evolution overpotential was 303 mV,and the Tafel slope was 69.22 mV·dec^-1 at a current density of 50 mA·cm^-2.At the same time,it is applied to both the cathode and anode electrode materials of electrolyzed water,and only 1.52 V can be used to obtain a current density of 10mA·cm^-2,while continuously electrolyzing at a current density of 10 mA·cm^-2 for12 h,the voltage changed only 27 mV,showing excellent electrocatalytic performance and good stability.