Study On Preparation Of Ni/Spinel Oxide Composite Electrode And Its Electrocatalytic Performance Towards Oxygen Evolution Reaction

Environment and energy is a premise of the human society for existence anddevelopment. So, Hydrogen as secondary clean energy gets wide attention. Now, thealkaline electrolysis H2O preparation H2is an important means of industrialpreparation of high purity H2, and electrolysis of H2O to some of the surplus lifepower can be saved into hydrogen, and energy conservation. However, the oxygenevolution overpotential is too high, it is a major cause electrolysis H2O process withhigh energy consumption, low efficiency. Therefore, the study of low oxygenevolution overpotential, high stability, and low cost of the anode material, has a veryimportant practical significance.In order to improve the electrocatalytic and stability of composite electrodetowards oxygen evolution reaction（OER）. Nickel, because of its resistance tocorrosion properties under alkaline conditions was selected to as the substrate in thearticle. We choose spinel-type oxide of NiFe₂O₄, NiCo₂O₄and Zn_1-xNixCo₂O₄because of its excellent electro-catalytic properties, corrosion properties, electricalconductivity, and chemical stability for OER as an electrode material. TheNi/NiFe₂O₄composite coating was prepared through composite electro-deposition;the Ni/NiCo₂O₄and Ni/Zn_xNi_1-xCo₂O₄composite coating was prepared throughdepositing.A series of spinel-type Zn_xNi_1-xCo₂O₄powders and NiFe₂O₄have beensynthesized by hydroxide co-precipitation method, through TG-DTA analysisaccurate preparation temperture. The spinel-type NiCo₂O₄powders have beensynthesized by sol-gel method. In order to enhance the electrode binding force toimprove the electrode stability, and reduce the internal resistance for improveelectro-catalytic properties. The Ni/NiFe₂O₄composite coating was prepared throughcomposite electro-deposition in Watt nickel plating by adding some NiFe₂O₄powders,As a result, the NiFe₂O₄mass content in the Ni/NiFe₂O₄composite coating was foundto be the highest（55.15%） at the best plating conditions of a solution pH=5.8～6.0 and a cathodic current density jk=40～60mA·cm-2. It So, to overcome the traditionalcoating poor adhesion and difficult to prepare a excellent adhesion thick coating, alarge surface area and uniform distribution of Ni/NiCo₂O₄composite coating wasprepared through composite sol combined with sintering. In order to overcome thelack of general coating method, the Ni/Zn_xNi_1-xCo₂O₄composite coating wasprepared by precursor coating method, the electrode have measurement accuracy, lowimpurity content and large surface area. The morphology、composition and structureof the different powders and their composite coatings were characterized by scanningelectron microscopy（SEM）, X-ray diffraction（XRD） and energy dispersivespectrometer（EDS）.In5mol·L-1KOH, the electro-catalytic properties towards oxygen evolutionreaction（OER） and the stability of the composite coating electrode was study by usingcyclic voltammertry（CV）, steady-state polarization, electrochemical impedancespectroscope（EIS）, chronoamperometry and constant potential electrolysis with longtime. It was found that the initial oxygen evolution potential from negative to positiveorder: Ni/NiCo₂O₄composite coating electrode（0.3V）, Ni/Zn0.3Ni0.7Co₂O₄compositecoating electrode（0.3V）, Ni/NiFe₂O₄composite coatings electrode（0.4V）, porous Nielectrode（0.5V）, Ni electrode（0.6V）, indicating that the electrocatalytic activity forthe oxygen evolution in OER turn from strong to weak. The EIS study the OERmechanism of different electrode: the Ni/NiFe₂O₄composite electrode isco-controlled by an electrochemical step and a diffusion step. The Ni/NiCo₂O₄coating electrode polarization play a major role; the control step of theNi/Zn_xNi_1-xCo₂O₄composite coating was the charge-transfer reactions and the Nernstdiffusion process combining control step. Constant potential electrolysis with longtime experiments to study the stability of different electrode, unden oxygen evolutionpotential, continuous electrolytic35h found that the stability of three electrodes arebetter.