Dual-Site Activation on 2D MoB Cocatalysts Enables Universal Charge-Transfer Acceleration for Photocatalytic Hydrogen Production and Biomass Valorization

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Abstract
Noble-metal-based cocatalysts remain the benchmark for interfacial charge extraction and lowering surface reaction kinetics barriers for photocatalytic water splitting, but their scarcity and cost limit scalable deployment. To search for low-cost alternatives, two-dimensional MoB nanosheets (MB) were introduced as an active, noble-metal-free cocatalyst platform. The near-ideal hydrogen adsorption free energies (|ΔGH*| ~ 0.15–0.18 eV) at Mo- and O-terminated edge sites, as well as at activated B basal-plane sites, will favor H2 evolution reaction kinetics. A Schottky-like junction forms when ultrathin MB is integrated with a semiconductor light absorber, which boosts ultrafast charge separation and transfer, as resolved by femtosecond transient absorption spectroscopy and Kelvin probe force microscopy. The universality of the MB 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 mmol g–1 h–1 under 420 nm light, while simultaneously promoting the oxidative valorization of benzyl alcohol (121.3 mmol g–1 h–1). Evidenced by ultrafast electron sink dynamics with 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.

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