Construction of Fe regulated NiMoN nanorods as an efficient electrocatalyst for overall water splitting and urea electrolysis

Rational design of low-cost, highly-efficient electrocatalysts for the hydrogen and oxygen evolution reactions (HER/OER) is critical to enable sustainable hydrogen production via water electrolysis. Herein, a novel nanorod array catalyst, Fe-NiMoN, has been rationally designed and directly grown on nickel foam (NF) via a facile hydrothermal method followed by nitridation treatment. The novel 3D porous nanorod architecture is favorable for providing abundant active sites, accelerating mass diffusion/electron transfer, and facilitating gas release. In addition, density functional theory (DFT) simulations reveal that Fe doping shifts the d-band center of NiMoN away from the Fermi level compared to the undoped NiMoN, thereby reducing the hydrogen adsorption free energy (ΔGH*) toward 0, which in turn enhances the HER activity. Consequently, the Fe-NiMoN catalyst delivers exceptional bifunctional electrocatalytic activity in alkaline media, requiring low overpotentials of 17 mV (HER) and 238 mV (OER) to achieve 10 mA cm-2. Notably, the Fe-NiMoN catalyst assembled into a two-electrode alkaline electrolyzer requires a voltage of only 1.504 V to achieve a current density value of 10 mA cm-2, with no performance declining after 100 h of steady operation. Moreover, for urea-assisted electrolysis, it can deliver 10 mA cm-2 at only 1.367 V. Overall, this work provides a strategy for synthesizing desirable electrocatalysts for green hydrogen production coupled with wastewater treatment.