Two-Dimensional Borophene–Transition Metal Dichalcogenide Heterostructure for Efficient Bias-Free Water Splitting under Concentrated Solar Illumination

Integrating solar energy with water electrolysis provides a sustainable pathway for green hydrogen (H2) production by eliminating dependence on fossil fuel-derived electricity. In this work, we demonstrate a solar-driven photovoltaic–electrolysis (PV–EC) device using a commercial triple-junction (3J) photovoltaic cell coupled with water electrolysis enabled by two-dimensional (2D) borophene–transition metal dichalcogenide (TMDC) heterostructure electrocatalysts. Borophene–MoS2 and borophene–WS2 were synthesized via liquid-phase exfoliation, and their heterostructured architecture was confirmed through comprehensive structural, morphological, and chemical characterization. The bifunctional borophene–TMDC heterointerface promotes an efficient charge-transfer and favorable reaction kinetics for both hydrogen and oxygen evolution reactions by lowering the activation energy at both electrodes. The integrated PV–EC system delivers Faradaic efficiencies exceeding 90% and achieves a solar-to-hydrogen (STH) efficiency of ∼6.7% under simulated solar illumination. This study demonstrates that the metallic nature of borophene acts as a conductive scaffold, overcoming the intrinsic limitations of TMDCs to achieve bias-free, solar-driven water splitting.