Structure-dependent photocatalytic decomposition of formic acid on the anatase TiO2(101) surface and strategies to increase its reaction rate

Formic acid is a typical molecule that is involved in a lot important solar energy conversion processes. We perform first-principles calculations on the molecular mechanism of its photocatalytic decomposition reaction (PCD) on the anatase TiO2(101) surface. We find that the reaction barrier is sensitively dependent on the adsorption structure of the molecule. The one-step PCD of the monodentate formic acid has a lower barrier than that of bidentate formate. Coadsorbed water molecules can transform the formate from a bidentate to a monodentate configuration which greatly lower its decomposition barrier. Water molecule can also induce the spontaneous dissociation of the formic acid molecule. The monodentate dissociated formic acid is stabilized by the hydrogen bonds which will slightly enhance the barrier for its photodecomposition. However, the reaction rate can be further enhanced if the hydrogens are removed (for example, by oxygen molecules). Therefore, using coadsorbate and deliberately introducing and removing hydrogen bonds can be two strategies to tailor the photoreaction rate of the molecules. (C) 2015 Elsevier B.V. All rights reserved.