Cost-effective and facile electrodeposited cobalt-sulfide as efficient electrocatalysts for enhanced alkaline urea and seawater oxidation reaction

Seawater electrolysis is a pivotal approach for hydrogen production. However, the sluggish oxygen evolution reaction (OER) occurring at the anode poses a significant obstacle to its practical application. Replacing the OER with the urea oxidation reaction (UOR), which has a lower theoretical voltage of −0.46 V, has the potential to decrease energy consumption. Nevertheless, the intricate six-electron process of UOR limits its efficiency. In this study, cobalt-sulfur (Co–S) electrocatalysts were synthesized on nickel foam via electrodeposition, using CoCl 2 ·6H 2 O and thiourea as the sources of Co and S, respectively. The optimized Co–S electrocatalyst exhibits low overpotentials: 412 mV in 1.0 M KOH freshwater and 469 mV in 1.0 M KOH seawater to reach 50 mA cm −2 . More importantly, the catalyst displays excellent catalytic activity (10 mA cm −2 at 1.400 V) as well as long-term stability for 50 h in 1.0 M KOH + 0.33 M urea seawater. The excellent performance of the catalyst is attributed to the synergistic effect between Co and S, which optimizes the electronic configuration and accelerates charge and electron transfer, thus significantly improves the kinetics of the reactions. Furthermore, the abundance of sulfur vacancies reduces the adsorption energy of urea and strengthens electron interactions, thereby enhancing the UOR. Additionally, the superhydrophilic/superaerophobic nature of the Co–S electrocatalyst facilitates the diffusion of gases and liquids, thus improving the OER/UOR performance.