Prolonged lifetime and enhanced separation of photo-generated charges of nanosized α-Fe2O3 by coupling SnO2 for efficient visible-light photocatalysis to convert CO2 and degrade acetaldehyde

To develop efficient visible-light photocatalysis on alpha-Fe2O3, it is highly desirable to promote visible-light-excited high-energy-level electron transfer to a proper energy platform thermodynamically. Herein, based on the transient-state surface photovoltage responses and the atmosphere-controlled steady-state surface photovoltage spectra, it is demonstrated that the lifetime and separation of photogenerated charges of nanosized alpha-Fe2O3 are increased after coupling a proper amount of nanocrystalline SnO2. This naturally leads to greatly improved photocatalytic activities for CO2 reduction and acetaldehyde degradation. It is suggested that the enhanced charge separation results from the electron transfer from alpha-Fe2O3 to SnO2, which acts as a proper energy platform. Based on the photocurrent action spectra, it is confirmed that the coupled SnO2 exhibits longer visible-light threshold wavelength (similar to 590 nm) compared with the coupled TiO2 (similar to 550 nm), indicating that the energy platform introduced by SnO2 would accept more photogenerated electrons from alpha-Fe2O3. Moreover, electrochemical reduction experiments proved that the coupled SnO2 possesses better catalytic ability for reducing CO2 and O-2. These are well responsible for the much efficient photocatalysis on SnO2-coupled alpha-Fe2O3.