Alkalized lychee-shell TiO2/WO3-5 heterojunctions with oxygen vacancies for enhanced CO2 photoreduction to methanol

Photocatalytic conversion of CO 2 into solar fuels presents a promising strategy for mitigating greenhouse gas emissions. The reduction of CO 2 to methanol not only enables carbon resource recycling but also facilitates the production of sustainable fuels. In this study, a litchi-shell-like TiO 2 /WO 3 -5 hollow heterojunction catalyst was constructed, featuring surface alkalization and abundant oxygen vacancies. This unique architecture provides a high specific surface area and plentiful active sites, thereby significantly enhancing CO 2 adsorption capacity. Under neutral conditions (pH = 7), the TiO 2 /WO 3 -5 catalyst achieves a remarkable methanol production rate of 780 μmol·g⁻¹ ·h⁻¹ with a high selectivity of 88.6 %, substantially outperforming its individual counterparts, pure TiO 2 and WO 3 . Furthermore, the catalyst demonstrates excellent stability over multiple reaction cycles. A series of characterizations, including EPR, PL, TRPL, and in situ DRIFTS, collectively verify the formation of a Z-type heterojunction, which effectively promotes the spatial separation of photoinduced charge carriers and suppresses the formation of CO and CH 4 . This work underscores the crucial synergy between Z-type heterojunction engineering and surface defect manipulation in enhancing reaction selectivity and efficiency. The TiO 2 /WO 3 -5 catalyst offers a prospective platform for CO 2 -to-fuel conversion and provides valuable guidance for the design of advanced photocatalysts.