Nickel-cobalt nitride nanoneedle supported on nickel foam as an efficient electrocatalyst for hydrogen generation from ammonia electrolysis

The generation of hydrogen from water electrolysis has been widely studied as a power-to-gas pathway for the change of energy consumption system, and has attracted a lot of scientific interest over the past several decades. However, the sluggish anodic oxygen evolution reaction (OER) leads to high overpotential in the electrolytic process. Therefore, using ammonia electrolysis to replace water splitting was recently considered as an advisable method for getting pure hydrogen, as ammonia electrocatalytic decomposition is thermodynamically more energy efficient than water splitting. Thus, in this work, a nanostructured transition metal binary (rather than the most widely used noble metals) deposited on nickel foam was developed through a hydrothermal method. The nickel-cobalt bimetallic catalyst was then further fabricated through the nitridation process annealed in an ammonia atmosphere at high temperatures to prepare nickel-cobalt nitride, which substantiated an optimal electrochemical performance on hydrogen evolution reaction (HER) in an alkaline ammonia system. The electrochemical tests indicated that the 1D nanoneedle nickel-cobalt nitride electrode offers favorable surface area and active sites leading to the hydrogen evolution onset potential close to zero, the overpotential 74 mV at 10 mA•cm−2, 138 mV at 100mA•cm−2, and the Tafel slope 67 mV/dec. In addition, it also demonstrated an excellent stability in long-term running, with the hydrogen generation rate slightly reduced after 10 h of chronoamperometry measurements. Moreover, the potential of ammonia electrolysis was 0.71 V at 100 mA•cm−2 in a two-electrodes system, lower than that of water splitting, suggesting the hydrogen production from ammonia electrolysis could be a promising alternative to water splitting.