Judging the feasibility of TiO as photocatalyst for chemical energy conversion by quantitative reactivity determinants.

In this study we assess the general applicability of the widely used P25-TiO in gas-phase photocatalytic CO reduction based on experimentally determined reactivity descriptors from classical heterogeneous catalysis (productivity) and photochemistry (apparent quantum yield/AQY). A comparison of the results with reports on the use of P25 for thermodynamically more feasible reactions and our own previous studies on P25-TiO as photocatalyst imply that the catalytic functionality of this material, rather than its properties as photoabsorber, limits its applicability in the heterogeneous photocatalytic CO reduction in the gas phase. The AQY of IrO/TiO in overall water splitting in a similar high-purity gas-solid process was four times as high, but still far from commercial viability.