Photocatalysis under thermally shifted bandgap

The heat effect on photocatalysis should be taken care because light absorption causes a temperature rise in semiconductor. In this research, bandgaps and action spectra of semiconductor photocatalysts were investigated at room and increased temperature. Throughout the photoelectrochemical, gas-phase, and liquid-phase photocatalysis experiments, we found that when the temperature is increased from room temperature to 75 or 90 °C, not only the absorption originating from the bandgap excitation of titanium dioxide (TiO2) but also the action spectrum of the photocatalytic reaction shifted to lower energy. This phenomenon implies that the photocatalytic reaction can be driven by light with lower energy when the band structure is ‘modified’ by heat energy. This result not only enables us to utilize more incident photons but also to control the reduction or oxidation ability. Thus, this ‘thermal modification’ of metal oxide semiconductors provides a new strategy for engineering the bands of semiconductor photocatalysts.