Surface oxygen vacancies on WO3 contributed to enhanced photothermo-synergistic effect

Abstract Photothermooxidation has demonstrated a high efficiency in the removal of volatile organic compounds in air. Among photothermocatalysts, attention is presently focused on composites of noble metal/metal oxide or metal oxide/metal oxide. Instead, in this work, we present a case of single oxide WO 3 subjected to hydrogen treatment as photothermocatalyst. With the increase of hydrogen treatment temperature, the color of WO 3 changes from yellow to blue to dark blue and a phase transition from WO 3 to WO 2.72 to WO 2 is accompanied, suggesting an increase of concentration of oxygen vacancy. Photothermocatalytic test against degradation of gaseous acetaldehyde at 60 °C under UV light shows that WO 3−x sample with low concentration of oxygen vacancy displays the most significant synergetic effect between photocatalysis and thermocatalysis. Its photothermocatalytic activity in terms of CO 2 evolution rate is 5.2 times higher than that of photocatalytic activity. However, WO 3 –WO 2.72 and WO 2 with high degree of oxygen deficiency show insignificant synergetic effect between photocatalysis and thermocatalysis. The reason for the different synergistic effect over above samples is believed to lie in balance between decreased activation energy of lattice oxygen and recombination of photogenerated electrons and holes induced by oxygen deficiency.