Synthesis of various morphologies of CoFe bimetallic hydroxides for enhanced oxygen evolution reaction performance

• CoFe bimetallic hydroxide nanosheets (CoFe BMH NSHs) exhibit superior oxygen evolution reaction (OER) activity with an overpotential of 282 mV at 100 mA·cm−2 and an overall water splitting voltage of 2.05 V. • The nanosheet morphology provides the largest electrochemically active surface area among the four synthesized morphologies, as evidenced by the highest double-layer capacitance (Cdl). • In situ Raman spectroscopy reveals that metal oxyhydroxide (MOOH) is the active species during OER, and its formation is irreversible. • This systematic study offers a design guideline for optimizing catalyst morphology to enhance performance in water splitting applications.