Optimization of CO ₂ Mass Transfer and Modulation of Reaction Kinetics for Efficient CO ₂ Conversion via a Three‐Phase Photocatalytic Flow System

Abstract The design of a photocatalytic system with conducive CO 2 mass transfer, reaction kinetics, and product venting is crucial for achieving stable and efficient photocatalytic CO 2 reduction reaction (CO 2 RR). Herein, a three‐phase photocatalytic flow system is developed to optimize the CO 2 mass transfer and modulate the reaction kinetics, and prepare single‐atom‐based photocatalyst to boost the performance of CO 2 RR. Kinetic calculations present that the flow system optimizes the first‐order reaction of the conventional non‐flow system to zero‐order reaction, which facilitates the efficient and long‐lasting photocatalytic CO 2 RR. Ab initio quantum chemical simulations of both the ground and excited states reveal that the enhanced performance stems from charge transfer photoexcitation associated with the doped single Co atom, which facilitates proton adsorption, reduces the energy barrier, and promotes C–OH bond cleavage. Taking advantage of the three‐phase flow system and single‐atom catalyst, the CO generation rate increases to 2.35 µmol h −1 with a selectivity of 97.8%. This work opens a new avenue for the rational design of high‐efficiency CO 2 conversion systems and holds promise for other photocatalytic applications.