Prolonged lifetime and enhanced separation of photo­generated 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 α-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 α-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 α-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 (~590 nm) compared with the coupled TiO₂ (~550 nm), indicating that the energy platform introduced by SnO₂ would accept more photogenerated electrons from α-Fe₂O₃. Moreover, electrochemical reduction experiments proved that the coupled SnO₂ possesses better catalytic ability for reducing CO₂ and O₂. These are well responsible for the much efficient photocatalysis on SnO₂-coupled α-Fe₂O₃.