Enhanced photothermal CO2 hydrogenation over In2O3−x/carbon nanotube composites

Abstract

Photothermal CO₂ reduction technology has garnered significant interest as a promising solution to mitigate the effects of greenhouse gases and address energy crises. Due to its unique physicochemical properties, In₂O₃ stands out as an excellent thermal catalyst for converting CO₂ to CO, with strong potential to drive the photothermal reverse water–gas shift (RWGS) reaction. However, synchronous tuning of the photothermal conversion efficiency and active site density of wide-bandgap In₂O₃, which inherently has a narrow light absorption range, remains a significant challenge. In this work, we established a novel protocol for synthesizing In₂O_3−x/carbon nanotube (CNT) composites through in situ photo-dehydration routes, forming heterojunction architectures. Benefiting from the strong light-harvesting capability and high thermal conductivity, CNTs and In₂O₃ exchange electrons, weakening O–In bonds, thereby promoting oxygen vacancy formation in surface regions. This structural and electronic modulation not only enhances the photothermal conversion efficiency of In₂O₃ but also improves its capability to activate CO₂. Consequently, the In₂O_3−x/CNT composite achieves a CO production rate of 552 mmol g⁻¹ h⁻¹ with near-unity selectivity. This work presents a general strategy to enhance surface temperature and defect engineering in oxide semiconductors without compromising selectivity, thereby advancing the field of photothermal catalysis.