Unveiling the Potential of Metal Diborides for Electrocatalytic Water Splitting: A Comprehensive Review

Electrocatalytic water splitting (EWS) driven by renewable energy is vital for clean hydrogen (H2) production and reducing reliance on fossil fuels. While IrO2 and RuO2 are the leading electrocatalysts for the oxygen evolution reaction (OER) and Pt for the hydrogen evolution reaction (HER) in acidic environments, the need for efficient, stable, and affordable materials persists. Recently, transition-metal borides (TMBs), particularly metal diborides (MDbs), have gained attention due to their unique layered crystal structures with multicentered boron bonds, offering remarkable physicochemical properties. Their nearly 2D structures boost electrochemical performance by offering high conductivity and a large active surface area, making them well-suited for advanced energy storage and conversion technologies. This review provides a comprehensive overview of the critical factors for water splitting, the crystal and electronic structures of MDbs, and their synthetic strategies. Furthermore, it examines the relationship between catalytic performance and intermediate adsorption as elucidated by first-principle calculations. The review also highlights the latest experimental advancements in MDb-based electrocatalysts and addresses the current challenges and future directions for their development.