Optimization of electrocatalytic properties of NiMoCo foam electrode for water electrolysis by post-treatment processing

Hydrogen is a potential alternative to fossil fuels in coping with the increased global energy demand, and water electrolysis is an attractive approach for H₂ production. Nickel–molybdenum–cobalt (NiMoCo) foam electrodes used for water electrolysis were prepared by the electrodeposition method, and the influence of heat treatments on the surface structure of NiMoCo foam electrodes, mechanical properties, and electrochemical performance of the synthesized electrodes was investigated in order to optimize the post-treatment processes. The residual carbon in the surface of the electrode was removed by decarbonization in the atmospheric condition. The carbon content decreases to lower than 200 × 10⁻⁶ when the temperature exceeds 500 °C. Next, the material is reduced in hydrogen atmosphere from 500 to 1100 °C to remove the surface oxides. As the temperature increases, the surface molybdenum content increases significantly between 500 and 800 °C, the surface grains become coarser, and the tensile strength and elongation increase as well. The lowest polarization overpotential is obtained at 800 °C. Below 800 °C, the electrode is only partially reduced and some black oxide zones are observed on the electrode surface, which leads to the higher polarization overpotential. The samples heat-treated at the temperatures of higher than 800 °C show better strength and toughness as well as brighter appearance. However, the surface particle coarsening leads to a decrease in the specific surface area and a higher overpotential.