Transient measurements of lattice oxygen in photocatalytic decomposition of formic acid on TiO2

In the absence of gas-phase O-2, formic acid extracted lattice oxygen from TiO2 during photocatalytic decomposition (PCD) at room temperature. The amo unt of oxygen extracted was, determined by interrupting PCD of a monolayer of formic acid after various reaction times and measuring O-2 uptake in the dark. After surface oxygen was depleted by PCD, oxygen diffused from the b ulk to replenish the surface oxygen vacancies. The rate of oxygen diffusion to the surface was determined by measuring O-2 uptake after various dark t imes. A small fraction of the CO2 that formed during PCD remained on the re duced sites of the TiO2 surface, but this CO2 was displaced by O-2 adsorpti on at room temperature.