Synthesis of various morphologies of CoFe bimetallic hydroxides for enhanced OER performance

CoFe bimetallic hydroxides (CoFe BMHs) are widely used as excellent catalysts in the field of water splitting. However, the influence of morphologies of CoFe BMHs on catalyst performance has not been systematically studied. In this study, we prepared CoFe BMHs nano-flowers (CoFe BMHs NFs), CoFe BMHs nano-sheets (CoFe BMHs NSHs), CoFe BMHs nano-rods (CoFe BMHs NRs), and CoFe BMHs nano-spheres (CoFe BMHs NSPs) on nickel foam using a hydrothermal method. Among them, CoFe BMHs NSHs exhibited the most beneficial catalytic activity. At a current density of 100 mA cm−2, the overpotential for oxygen evolution reaction (OER) was 282 mV, and the overall water splitting voltage was 1.923 V. The Cdl value of CoFe BMHs NSHs is the largest in CoFe BMHs, which proves that CoFe BMHs NSHs have the largest active area. Furthermore, the active site in the OER process was found to be MOOH by in situ Raman characterization and the generation of the active substance is an irreversible process. This work provides significant insights into the design of catalyst morphologies, offering valuable guidelines for enhancing the performance of other catalysts.