Cobalt–nickel composite nano-grass as an excellent electrode for urea oxidation†

Abstract

Urea-contaminated wastewater requires extensive energy for proper treatment before safe discharge to the surroundings. Direct urea fuel cells (DUFCs) could be utilized efficiently to treat urea-polluted water and generate electricity. The precious/expensive catalyst utilized at the electrodes is one of the main significant challenges to DUFC commercialization. In this study, a non-precious standalone electrode cobalt–nickel composites directly formed using a facile hydrothermal method on a highly porous conductive nickel foam (NF) surface. The developed electrode has an excellent nano-grass morphology and demonstrates outstanding activity towards urea electro-oxidation. Using a 0.33 M urea, the current density @ 0.5 V (vs. Ag/AgCl) in the case of the cobalt–nickel composite with the nano-grass electrode (Co/NF) is significantly higher than that obtained using the bare NF electrode. At the same conditions, the Co/NF electrode is successfully operated for a long term (24 h) with a slight degradation in the performance, with no effect on the surface morphology. The steady-state current generated after 24 hours of cell operation is twenty times that obtained using the bare NF. The perfect performance of the modified electrode is related to the synergetic effect between Ni and Co, excellent nano-grass morphology, and ease of charge transfer. The prepared materials on the surface of the NF have a high electrochemically active surface area of 44 cm² that is significantly higher than that of bare NF.