Deep CO₂photoreduction by synergy of K⁺doping and defective modulation over TiO₂@K₂Ti₆O₁₃nanoribbon heterojunctions

The contemporary issues of energy shortages and global warming, attributable to the substantial utilization of fossil fuels, require immediate consideration and remedial action. Photocatalytic CO2 reduction (CO2RR) technology is a promising approach to mitigate climate change and address current energy shortages. However, slow charge dynamics and low affinity for intermediates on photocatalysts remain significant challenges in photocatalytic CO2 reduction. In this study, we have synthesized a series of TiO2@K2Ti6O13 (KTO) heterojunctions for gas-solid phase photocatalytic CO2 reduction by incorporating K-doped defective TiO2 during the construction of KTO nanoribbons using a simple hydrothermal method. The presence of oxygen vacancies and the formation of type II heterojunctions provided a driving force for the transfer of photoexcited carriers, which modulated the electronic properties of the catalyst surface through the built-in electric field. Density functional theory (DFT) calculations and experimental results show that in Ov-K/TiO2, K+ doping and oxygen vacancies (Ov) synergistically modulate the charge density of Ti active sites, thereby promoting the adsorption and activation of CO∗intermediates. This enhancement resulted in Ov-K/TiO2@KTO-2 exhibiting improved CO2 conversion capacity and enhanced CH4 selectivity. This work provides a simple method to synthesize efficient TiO2-based photocatalysts for selective CH4 production and also offers a general platform for designing high-performance synergistic catalysts for efficient solar energy conversion.