The role of electron interfacial transfer in mesoporous nano-TiO2 photocatalysis: a combined study of in situ photoconductivity and numerical kinetic simulation

In this research, a combination of in situ photoconductivity (σ) and kinetic simulations was used to study the role of electron interfacial transfer (IT) in the gaseous photocatalysis of formic acid by mesoporous nanocrystalline TiO2. The effects of light intensity, initial formic acid concentrations, oxygen amounts, and temperature on the in situ σ and the photocatalytic courses were studied in detail. The temperature dependence of in situ σ clearly shows that the electron transfer is determined by the IT of electrons to O2 rather than by the transport. It was seen that the electron IT limits the photocatalysis by correlating with the recombination and the hole IT via the dynamic change in electron densities. The numerical simulation of in situ σ shows that the IT of electrons belongs to a thermally activated process that presents a thermal barrier of 0.5 eV. It is considered that this high thermal barrier limits the IT of electrons. It was also seen that the thermal activation of photocatalysis does not relate to that of the electron IT, although the overall photocatalysis is limited by the IT of electrons. Our finding shows that it is an effective way to increase the photocatalytic activity by reducing the thermal barrier of electron IT.