Enhanced photocatalytic performance of nanocrystalline TiO ₂ membrane by both slow photons and stop-band reflection of photonic crystals

An nc-TiO ₂/SnO ₂ inverse opal composite membrane was fabricated, the photo-activity of which was significantly enhanced by utilizing both slow photons and stop-band reflection of the photonic crystal layer. The materials of the photonic crystal layer must be transparent in the area of adsorption edge of the nc-TiO ₂, so that SnO ₂, having much greater electronic band gap than TiO ₂, was used for the materials of the photonic crystal layer. The photonic band-gap of the SnO ₂ photonic crystal was designed at the semiconductor band gap of TiO ₂ to harvest slow photons in the interface between the SnO ₂ layer and the TiO ₂ layer. The two layer structure makes it possible to couple the stop-band reflectivity of the photonic layer to the photocatalyst. Composite membranes can improve solar energy harvesting and substantially improve photocatalysts for photolysis and photochemical degradation of environmental pollutants.