The Research Of Coprecipitation Preparation Of NiCo₂O₄Electrode And Doped Modification

Face the dual pressures of energy shortage and environmental pollution, the world all strive to develop the new energy to replace fossil fuels. H2was recognized as the most promising green energy in the future. It is possible the ideal secondary energy to solve the shortage of resources and environmental pollution. Among numerous hydrogen production methods, the electrolysis water technology is considered as the most likely large-scale application. It has many advantages, such as:the relatively simple preparation process, the possibility of completely automated, the simple operating method and high purity of the product. However, the amount of hydrogen produced by electrolysis of water occupied only4%total amount of hydrogen, which is mainly due to the excessive energy consumption of electrolysis water process, where the anodic oxygen evolution reaction is the largest energy consumption part, electrode material poor stability, poor conductivity properties of the oxide electrode material. Therefore, seeking for appropriate anodic oxygen evolution has been a key for electrolysis water technology, namely looking for inexpensive, high catalytic activity, good stability, long life oxygen evolution catalyst.NiCo2O4and NiCo2O4-rGO were prepared through the hydroxide coprecipitation method. The structures and morphologies of samples were characterized by a variety of method, such as TG, XRD, SEM, TEM, EDS and BET. The catalysts electrodes were prepared by coating the water suspension of the catalysts powder, respectively. At the same time, the electrocatalytic properties of electrodes for oxygen evolution were tested by cyclic voltammetry (CV), electrochemical impedance (EIS), Tafel curves and controlled potential electrolysis test in0.1mol/L KOH (pH=13) under normal temperature and pressure. The main contents and conclusions are:First, NiCo2O4were prepared through the hydroxide coprecipitation method. The oxides consist of loosely porous rough particles. The sample shows an average pore diameter of12.3nm and a specific surface area of88.7m2/g. When Ni/Co ion ratio were1:2, the calcination temperature was350℃for8h, NiCo2O4/Ti had the best oxygen evolving activity:in0.1mol/L KOH (pH=13) under normal temperature and pressure, its Tafel slope was85.9mV/dec and it had the lowest overpotential at i=10mA/cm2,345mV vs NHE, Electrolysis current density were about original63%after5.5h.Second, NiCo2O4-rGO hybrid materials were prepared through adding a certain amount of rGO in mixed solution of ethylene glycol and a little water containing Ni/Co with ion ratio1:2. NiCo2O4nanoparticles grew sporadically in the sheet rGO, formed the rod-shaped spheres mixed with velvet-like sphere morphology. The sample shows an average pore size of68.06nm and a specific surface area of139.5m2/g. When stirred at25℃for18h, the amount of mixed were8mg, rGO were initial material, the calcination temperature was300℃for8h, NiCo2O4-rGO/Ti had the best oxygen evolving activity：in0.1mol/L KOH (pH=13) under normal temperature and pressure, contact resistance between NiCo2O4-rGO/Ti and the solution was50Ω, its Tafel slope was81.5mV/dec and it had the lowest overpotential at i=10mA/cm,307mV vs NHE, Electrolysis current density were about original80%after5.5h.