ZnO-Enhanced Cu/ZrO2 for Photothermal Catalytic CO2 Hydrogenation to Methanol

Abstract The photothermal conversion of CO2 to methanol represents a sustainable pathway for energy storage and carbon neutrality. However, most highly active photothermal catalysts have been evaluated under Xenon-lamp irradiation, in which the photothermal effect arises predominantly from the infrared region. This practice may therefore lead to an underutilization of the ultraviolet (UV) spectrum available in natural solar light. To address this limitation, we designed a composite catalyst by strategically incorporating the semiconductor ZnO into a Cu/ZrO2 system. This design enables complementary light absorption: Cu effectively harnesses visible/near-infrared light, while ZnO extends the response into the UV range. Comprehensive characterizations confirm that the introduction of Zn significantly enhances the light-harvesting capability without altering the Cu active sites. Consequently, the optimized Cu/ZrO2–ZnO catalyst exhibits a remarkable enhancement in photothermal reaction, particularly under UV light, while maintaining CO2 hydrogenation activity. When evaluated under concentrated real sunlight, the catalyst achieves a methanol production rate of 2.7 mmol g–1 h–1, attributable to its efficient full-spectrum utilization. This work not only provides an efficient catalyst for CO2 hydrogenation but also demonstrates a general strategy for maximizing solar energy conversion in photothermal catalysis.