Electron paramagnetic resonance study of the interaction of the ZnO surface with air and air–reducing gas mixtures

Abstract

The variation of the defect number that results from the interaction of ZnO with air–reducing gas mixtures (H₂–air and CO–air) has been investigated by EPR spectroscopy. It appears that up to 573 K the surface interaction with CO or H₂ and air is dominated by the reaction of CO or H₂ with the chemisorbed oxygen species (O^–₂ and O^–); at higher temperature the main process is the formation of new oxygen vacancies. The CO effect is stronger than that of H₂ up to 573 K; after this temperature the relative importance reverses and H₂ is more efficient than CO in producing new oxygen vacancies.