Thin-water-film-enhanced TiO 2 -based catalyst for CO 2 hydrogenation to formic acid.

Carbon dioxide (CO 2 ) hydrogenation can not only mitigate global warming, but also produce value-added chemicals. Herein, we report a novel three-phase catalytic system with an in situ generated and dynamically updated thin water film covered on the noble-metal-free TiO 2 -based catalyst for highly efficient CO 2 hydrogenation, realizing a four-time enhancement compared with that with the catalyst suspended in water. The water film plays dual roles by directly participating in the reaction and removing the produced oxygenates (mainly formic acid) from the catalyst surface by dissolution. These results demonstrate an effective design for CO 2 hydrogenation, which will open a new door to three-phase catalysis.