Dual-site activation on two-dimensional molybdenum monoboride cocatalysts enables universal charge-transfer acceleration for photocatalytic hydrogen production and biomass valorization.

Abstract

Noble-metal-based cocatalysts remain the benchmark for interfacial charge extraction and lowering surface reaction barriers for photocatalytic water splitting, but their scarcity and cost limit scalable deployment. To develop low-cost alternatives, two-dimensional molybdenum monoboride nanosheets (MoB, denoted as MB) were introduced as an active, noble-metal-free cocatalyst platform. On the basal plane, O/Mo and B sites work in synergy to optimize charge transfer and proton reduction, affording hydrogen adsorption free energies (|ΔGH⁎| ∼0.121-0.560 eV), with the most favorable sites close to 0.121 eV. A Schottky-like junction forms when ultrathin MB is integrated with a semiconductor light absorber, boosting ultrafast charge separation and transfer, as resolved by femtosecond transient absorption spectroscopy and Kelvin probe force microscopy. The universality of MB as a cocatalyst in accelerating reaction kinetics was confirmed across diverse semiconductor photocatalysts. An optimized Zn3In2S6/MB hybrid (ZMB-4) achieved a remarkable H2 evolution rate of 147.1 ± 4.3 mmol g-1 h-1 under 420 nm light, while simultaneously promoting the oxidative valorization of benzyl alcohol (121.3 ± 1.2 mmol g-1 h-1). Supported by its ultrafast electron transfer dynamics and multi-site surface activation, this work identifies two-dimensional MoB as a low-cost and universal cocatalyst platform for producing solar fuel and value-added chemicals.