Synergy between Ti single atoms and Ti nanoparticles for promoted photocatalytic CO2 reduction to CH4 over zeolite L/TiO2

Developing efficient photocatalysts with high activity and selectivity for CO 2 methanation remains a significant challenge. Herein, we report a heterostructured photocatalyst composed of Zeolite L/TiO 2 (ZL/TO), with both Ti single atoms (SAs) and Ti nanoparticles (NPs) anchored on the TO surface. Comprehensive characterizations and density functional theory (DFT) calculations reveal that the synergy between Ti SAs and Ti NPs promotes the separation and transfer of photogenerated charge carriers through a type II heterojunction mechanism, leading to a preferential accumulation of photogenerated electrons on the Ti NPs for CO 2 photoreduction. Furthermore, the Ti NPs play a dual role in the reaction: they not only stabilize the key CO* intermediate, thereby promoting its subsequent exothermic protonation steps, but also facilitate the desorption of the final CH 4 product from the photocatalyst surface. Consequently, using only water vapor and without any sacrificial agents, the optimal photocatalyst achieves a high CH 4 production rate of 49.26 μmol·g −1 ·h −1 with a selectivity of 95.0 %, which is comparable to the performance of state-of-the-art photocatalysts. This work provides a feasible strategy for effective photocatalytic CO 2 methanation by leveraging the synergy between metal SAs and NPs loaded on a semiconductor support.