Fine-tunable N-doping in carbon-coated CoFe nano-cubes for efficient hydrogen evolution in AEM water electrolysis

To obtain environment-friendly and renewable hydrogen energy, research is being actively conducted towards lowering the hydrogen evolution reaction (HER) energy barrier through various modifications to the surface of a transition metal bimetal electrochemical catalyst. Herein, we report the development of highly N-doped carbon shell-encapsulated cobalt iron nano cube (CoFe@HNCS) through fine-tuning of the nitrogen-doping content in the carbon shell. The pyridinic N-rich N-doped carbon shell, achieved by adding melamine through electrostatic interactions, improves conductivity, increases active sites, and optimizes Gibbs free energy for hydrogen adsorption. In alkaline HER performance, the optimized CoFe@HNC20 exhibits a lower overpotential (98.2 mV) than CoFe@NCS (133.2 mV) at 10 mA cm⁻². Furthermore, CoFe@HNCS20 as cathode catalyst in anion exchange membrane (AEM) water electrolyzer also shows low cell voltage of 1.808 V to achieve the current density of 0.5 A cm⁻². The expansion of the application to combine solar cells and AEM electrolyzer suggests the possibility of a hydrogen ecosystem.