Evaluating a Second Time Scale for Hole Extraction in an Actual Photocatalytic Reaction: The Method.

Photoinduced hole extraction, which is widely believed to occur on the picosecond-nanosecond time scale, exhibits sensitive correlation with semiconductor-cocatalyst interfacial electron transfer that occurs on a second time scale in a photocatalytic reaction. This inherent correlation means that the required high density of electrons for overcoming the potential barrier severely suppresses the survival and interfacial extraction of photogenerated holes. We here propose to evaluate the time constant for the occurring hole extraction by separately monitoring the rise and decay of the photoinduced potential. The evaluated second time scale indicates that hole extraction crucially influences the actual photocatalytic reaction. To improve photocatalytic photon utilization, we facilitate hole extraction by lowering the semiconductor-cocatalyst contact barrier.