Deep CO2 photoreduction by synergy of K+ doping and defective modulation over TiO2@K2Ti6O13 nanoribbon 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 (O_v) synergistically modulate the charge density of Ti active sites, thereby promoting the adsorption and activation of CO* intermediates. This enhancement resulted in O_v-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.