Abstract
In the pursuit of utilizing renewable energy sources for green hydrogen (H(2)) production, alkaline water electrolysis has emerged as a key technology. To improve the reaction rates of overall water electrolysis and simplify electrode manufacturing, development of bifunctional electrocatalysts is of great relevance. Herein, CoPBO/Co(3)O(4) is reported as a binary composite catalyst comprising amorphous (CoPBO) and crystalline (Co(3)O(4)) phases as a high-performing bifunctional electrocatalyst for alkaline water electrolysis. Owing to the peculiar properties of CoPBO and Co(3)O(4), such as complementing Gibbs free energy values for H-adsorption (ΔG (H)) and relatively smaller difference in their work functions (ΔΦ), the composite exhibits H(2) spillover (HS) mechanism to facilitate the hydrogen evolution reaction (HER). The outcome is manifested in the form of a low HER overpotential of 65 mV (at 10 mA cm(-2)). Moreover, an abundant amount of surface oxygen vacancies (O(v)) are observed in the same CoPBO/Co(3)O(4) composite that facilitates oxygen evolution reaction (OER) as well, leading to a mere 270 mV OER overpotential (at 10 mA cm(-2)). The present work showcases the possibilities to strategically design non-noble composite catalysts that combine the advantages of HS phenomenon as well as O(v) to achieve new record performances in alkaline water electrolysis.