The development of a highly efficient electrocatalyst for the hydrogen-evolution reaction (HER) plays a vital role in the process of water splitting. Two-dimensional (2D) materials are crucial for the HER due to having a large surface-to-volume ratio, tunable electronic properties, and abundant active sites, which collectively enhance their catalytic efficiency and lower the energy barriers for hydrogen production. Boron oxide (BO) is a recently synthesized light-elements-based 2D material that has not been extensively studied yet. The present work delves into the catalytic performance of pristine and single transition metal-decorated BO monolayer (TM@BO, TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Mo, Ru, Rh, Pd, Ag, Ir, Pt, or Au) for the HER using first-principles density functional theory calculations. The pristine BO monolayer exhibits an indirect band gap with a larger value of Gibbs’ free energy change $\mathrm{\Delta }G=2.33\mathrm{eV}$ as compared with the expected value for an efficient catalyst ($\mathrm{\Delta }G\sim 0\mathrm{eV}$). In contrast, Ti@BO and Fe@BO monolayers exhibit excellent HER performance with extremely low overpotential values around $-0.04\mathrm{eV}$ and 0.004 eV, respectively. The thermal stability of the Ti@BO and Fe@BO systems is confirmed through the AIMD simulations with minimal changes in the bond length and energy. The charge density difference and Bader charge analysis indicate a strong interaction of Ti and Fe on BO due to charge transfer from the metal d orbital to the 2p orbital of oxygen. The room-temperature electron mobility of the Ti@BO exhibits significant enhancement around ($52.96\times {10}^4{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$). The study of the reaction mechanism through the climbing image nudged elastic band method using the Volmer, Heyrovsky, and Tafel scheme under acidic and alkaline media shows that the Volmer–Heyrovsky reaction is the dominant mechanism for both the Fe@BO and Ti@BO monolayers, with the Volmer mechanism as the rate-determining step. However, under an alkaline medium, the HER process is less favorable due to the presence of large energy barriers. Our calculations predict a promising single-atom catalyst-based BO monolayer, which can be useful for its device application in energy conversion and storage.

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• Chemical kinetics, dynamics & catalysis
• Electrochemical properties
• Electrochemistry
• Hydrogen evolution reaction
• 2-dimensional systems
• Monolayer films
• Oxides
• First-principles calculations