Surface Modification of Co₃O₄ by HfO₂ for Efficient Bifunctional Electrocatalyst for Hydrogen and Oxygen Evolution

This study investigates the significant enhancement of electrocatalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) achieved through surface modification of cobalt oxide (Co 3 O 4 ) with hafnium dioxide (HfO 2 ). A mechanochemical approach is used to synthesize the surface‐modified catalyst, optimizing the electronic properties and active site accessibility of Co 3 O 4 to attain superior electrocatalytic performance. X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) characterization techniques confirmed the successful integration of HfO 2 into the Co 3 O 4 structure, resulting in an altered surface morphology and improved electronic conductivity. Electrochemical assessments demonstrate that the Co 3 O 4 /HfO 2 composite material exhibits exceptionally low overpotentials of 262 and 167 mV for the OER and HER, respectively, at a current density of 10 mA cm −2 . These values significantly outperform those of unmodified Co 3 O 4 , which presents overpotentials exceeding 467 and 311 mV for the OER and HER, respectively. High mass activity and turnover frequency (TOF) values are observed for the Co 3 O 4 /HfO 2 composite, highlighting the catalyst's efficiency. This outstanding performance is attributed to enhanced charge transfer kinetics and optimized electronic interactions facilitated by the HfO 2 modification. Consequently, this study underscores the potential of the Co 3 O 4 /HfO 2 composite as a cost‐effective and efficient electrocatalyst for water‐splitting applications, reveal advancements in renewable energy technologies.