Mechanism-Guided Design of Photocatalysts for CO₂ Reduction toward Multicarbon Products

Photocatalytic reduction of CO₂ to high value-added multicarbon (C₂₊) products is an important way to achieve sustainable production of green energy but limited by the low efficiency of catalysts. One fundamental issue lies in the high complexity of catalyst structure and reaction process, making the rational catalyst design and targeted performance optimization a grand challenge. Herein, we performed a mechanism-guided design of photocatalysts for CO₂ reduction by using the experimentally reported Cu doped TiO₂ (Cu-TiO₂) with high C₃H₈ selectivity and well-defined structure as the prototype. Our mechanistic study highlights three key factors for C₃H₈ formation, i.e., formation of double O vacancies (V_di‑O) for selectivity, C–C coupling for activity, and V_di‑O recovery for durability. More importantly, V_di‑O formation/recovery and C–C coupling are negatively correlated, indicating that ideal candidates should achieve a balance between oxygen vacancy (V_O) formation and C–C coupling. On this basis, TiO₂ with the doping of two adjacent Cu atoms (Cu-Cu-TiO₂) was designed with enhanced performance for CO₂ photoreduction toward C₃H₈. Furthermore, a simple descriptor (N_μ, “effective d electron number”) based on inherent atomic properties was constructed to uncover the underlying causes of the performance variation of different systems. These results provide new insights into the “structure–performance” relation of metal oxide-based photocatalysts, thus offering useful strategies for the rational design of excellent catalysts for CO₂ photoreduction.