Rational design of Cu oxynitride-BiVO₄ composites as enriched bifunctional electrocatalysts for hydrogen and oxygen evolution reaction performances

This study investigates the integration of copper oxynitride (CuON) and bismuth vanadate (BiVO₄) to form a bifunctional electrocatalyst with enhanced performance for the hydrogen and oxygen evolution reactions (HER and OER, respectively) in 1 M KOH. Structural and chemical analyses confirmed the successful construction of the CuON-BiVO₄ composite. Electrochemical studies demonstrated its superior catalytic performance, characterized by lower overpotentials (47 mV for the HER and 460 mV for the OER) and improved Tafel slopes (85 and 65 mV dec⁻¹) compared to its individual components. Moreover, its improved electrochemical surface area and reduced charge transfer resistance (∼7.5 Ω) indicated efficient charge transport. The CuON-BiVO₄ catalyst demonstrated excellent durability, maintaining stable performance for 24 hours. As a bifunctional electrode, the CuON-BiVO₄‖CuON-BiVO₄ electrolyzer required 1.68 V to achieve 10 mA cm⁻². These results highlight the synergistic interaction between CuON and BiVO₄, providing a cost-effective and durable catalyst for sustainable hydrogen production and advancing next-generation water-splitting systems.