Synergistic Effect of Rutile and Brookite TiO 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 TiO for O-H and C-H cleavage in HCOOH. Further, brookite TiO is beneficial to the generation of the OH radical and significantly promotes C-H cleavage in formate. Under optimized conditions, the H production efficiency of FA dehydrogenation can reach up to 30.4 μmol·mg·h, which is the highest value compared with similar reported TiO-based systems and over 1.7 times the reported highest value of AuPd/TiO photocatalysts. More importantly, after more than 42 days (>500 h) of irradiation, the system still demonstrated high H 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.