A Bis-tetraminobenzoquinone-Sensitized System for Hydrogen Evolution: The Double-Edged Influence of the NIR-Induced Photothermal Effect

The sensitization of semiconductors with organic photosensitizers represents an effective strategy for broadening their light absorption range, and increasing attention has been paid to the development of organic photosensitizers with a response to near-infrared (NIR) light. Notably, the influence of the photothermal effect induced by NIR on the performance of sensitized semiconductor systems, especially on the generation and separation of charge carriers, remains unclear. Herein, we construct a bis-tetraminobenzoquinone (TAQ)-sensitized TiO 2 system via a facile in situ solvothermal method to enable the light absorption of the composite up to ca. 1600 nm. Under visible–NIR light irradiation, the optimal TiO 2 /TAQ demonstrates a hydrogen evolution activity of 11.25 μmol g –1 h –1 , confirming that the photogenerated electrons produced by TAQ can transfer to TiO 2 for proton reduction. Notably, upon excluding NIR light, the TiO 2 /TAQ composite exhibits enhanced hydrogen evolution performance (up to 26.44 μmol g –1 h –1 ). Thermal images reveal that TAQ generates a significant photothermal effect under visible–NIR light. The temperature-controlled experiments and characterizations suggest that while elevated temperature helps to suppress charge carrier recombination and reduce charge-transfer resistance in the TiO 2 /TAQ-sensitized system, it simultaneously hinders the generation of charge carriers in TAQ. Such double-edged effects ultimately diminish the photocatalytic activity of TiO 2 /TAQ under visible–NIR light as compared to visible light irradiation. This work provides new insights into the generation and transfer of charge carriers from the photosensitizer under NIR light and offers guidance for the future development of highly efficient organic–inorganic sensitization systems.