Water splitting by CoFeLDH@NiFeS nanoelectrocatalyst assisted urea electrooxidation reaction

In this paper, NiFeS@CoFeLDH nanostructure was synthesized for the first time by electrochemical method in two steps. In the first stage, the first layer of NiFeS was deposited on the nickel foam (NF) substrate, and in the second stage, the second layer of cobalt-iron layered double hydroxide (CoFeLDH)by controlling the electrodeposition condition was deposited on the first. The deposition time and potential were optimized. The optimized NiFeS@CoFeLDH coating on NF has promising hydrogen evolution reaction (HER) activity, which exhibits small overpotentials of -191.5, and -304.0, at the current densities of -10, and -100 mA. cm−2, respectively. Furthermore, the synthesized NiFeS@CoFeLDH electrocatalyst only needs 358 mV overpotentials to operate at a current density of 10 mA. cm−2 indicating its great performance for the urea oxidation reaction (UOR). The electrode stability was examined at an industrial scale current density of -100 and 10 mA. cm−2 for HER and UOR respectively, which showed a very stable response for at least 10 h. The results showed that the simultaneous application of NiFeS and CoFeLDH electrocatalysts has a synergistic effect that increases the surface-to-volume ratio and improves the active sites. According to high performance for HER and UOR and also simple, fast, and binder-free synthesis without using expensive materials for preparing the electrocatalyst layer, the proposed electrode can be used as a good candidate for water splitting in the presence of urea.