Construction of coordination bond electron bridge boosting interfacial electron transfer to enhance bifunctional photocatalytic activity of TiO2/g-C3N4 heterojunction

The weak interfacial coupling of heterojunction catalysts leads to a large barrier, which inhibits interfacial electron transfer and limits the catalytic efficiency. Herein, a unique Ti-N coordination electron bridge has been designed and constructed in TiO2/g-C3N4 heterojunction with a tightly-coupled interface by using a newly designed topotactic transition and in-situ pyrolysis method. Experimental data and characterization analyses indicate that abundant stacking faults and surface oxygen vacancies change the surface atomic coordination environment and induce the formation of Ti-N coordination bond electron bridges. XPS, TA-PL probing experiment, and EPR analysis indicate a S-scheme electron transport mechanism. The synergistic effect of internal electric field and Ti-N electron bridge promote the efficient S-scheme electron transport, which facilitates the spatial separation of strong oxidizing holes and strong reducing electrons. The hierarchical nanoflower structure benefits electrolyte diffusion and reaction species adsorption. The above virtues endowed the catalyst with enhanced bifunctional photocatalytic activity for hydrogen evolution (1.89 mmol·g−1·h−1) and methyl blue degradation (0.114 min−1), which are 3.2 and 1.9 times that of the bare TiO2. This work opens a new avenue for the construction of heterojunctions and the optimization of interface carrier transfer, providing important insights for synthesizing photocatalysts with excellent activity and stability.