Ultrathin MXene “bridge” to accelerate charge transfer in ultrathin metal-free 0D/2D black phosphorus/g-C3N4 heterojunction toward photocatalytic hydrogen production

[Display omitted] •An uncomplicated method constructs an optimal BQ/TiC/UCN composite.•BQ/TiC/UCN demonstrates superior photocatalytic activity in visible light region.•The TiC nanosheets can accelerate the migration of photoinduced charge carriers.•The mechanism of charge transfer in BQ/TiC/UCN heterojunction is proposed. The fabrication of ultrathin MXene (Ti3C2)-based photocatalysts is highly intriguing as the charges can vectorially transfer along the two-dimensional (2D) direction despite being challenging. Herein, ultrathin Ti3C2 (TiC) nanosheets with excellent conductivity are rationally introduced to ultrathin metal-free 0D/2D black phosphorus (BQ)/ultrathin g-C3N4 (UCN) heterojunction for improving photocatalytic H2 production activity. The optimized BQ/TiC/UCN composite displayed obvious advantages such as the strong interfacial contact and enhanced visible-light capture. Importantly, the incorporation of TiC nanosheets substantially accelerates charge transfer to fast separation of photoinduced carriers between BQ and UCN. The optimized BQ/TiC/UCN composite exhibited 47.2 and 19.4 folds higher photocatalytic activity (18.42 mmol h−1 g−1) than that of bulk g-C3N4 (BCN) and UCN, respectively. The microstructure, composition, and optical properties of BQ/TiC/UCN composite were carefully characterized. The current research results may furnish fresh insights into the exploration of MXene (Ti3C2)-based catalysts with high solar energy utilization.