Synergistic Effect of Rutile and Brookite TiO₂ for Photocatalytic Formic Acid Dehydrogenation

Solar energy is an ideal clean and inexhaustible energy source. Solar-driven formic acid (FA) dehydrogenation is one of the promising strategies to address safety and cost issues related to the storage, transport, and distribution of hydrogen energy. For FA dehydrogenation, the O-H and C-H cleavages are the key steps, and developing a photocatalyst with the ability to break these two bonds is critical. In this work, both density functional theory (DFT) calculation and experimental results confirmed the positive synergistic effect between brookite and rutile TiO₂ for O-H and C-H cleavage in HCOOH. Further, brookite TiO₂ is beneficial to the generation of the ^•OH radical and significantly promotes C-H cleavage in formate. Under optimized conditions, the H₂ production efficiency of FA dehydrogenation can reach up to 30.4 μmol·mg^-1·h^-1, which is the highest value compared with similar reported TiO₂-based systems and over 1.7 times the reported highest value of Au_0.75Pd_0.25/TiO₂ photocatalysts. More importantly, after more than 42 days (>500 h) of irradiation, the system still demonstrated high H₂ production activity, indicating the potential for practical application. This work provides a valuable strategy to improve both the efficiency and stability of photocatalytic FA dehydrogenation under mild conditions.