Single-metal atoms supported on HfBO MBenes for efficient overall water splitting.

Two-dimensional hexagonal MBenes (h-MBenes), derived from h-MAB phases, exhibit great potential for electrochemical applications due to their unique electronic and catalytic properties. Using first-principles calculations, we explored single-atom transition metals (TMs) supported on h-MBene HfBO (TM@HfBO) as bifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). TM@HfBO structures demonstrated excellent thermal stability and high electrical conductivity, making them suitable for electrocatalysis. For HER, Nb@HfBO showed outstanding activity with a near-ideal hydrogen adsorption free energy (Δ = -0.01 eV), surpassing even platinum. For OER, ferromagnetic TM@HfBO systems (TM = Fe, Co, Ni) exhibited high catalytic potential, with Ni@HfBO achieving the lowest overpotential ( = 0.48 V), outperforming IrO ( = 0.56 V). These results highlight TM@HfBO as a promising alternative to noble-metal-based catalysts. Our findings provide a foundation for designing cost-effective, high-performance electrocatalysts for overall water splitting and underscore the potential of HfBO-based materials in sustainable energy applications.