Porous fixed-bed photoreactor for boosting C–C coupling in photocatalytic CO₂ reduction

Solar-driven CO₂ conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer. Here, a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C–C coupling in photocatalytic CO₂ reduction. The photocatalytic results show that ∼90% selectivity towards C2+ products is obtained by a Cu/Cd_0.5Zn_0.5S photocatalyst, with a yield of 6.54 ​μmol/h (an irradiation area of 0.785 cm²), while only 0.94 ​μmol/h (an irradiation area of 19.625 cm²) is achieved with a commonly used suspension photocatalytic reactor. We find that under the same CO₂ feed rate, the local CO₂ concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension photoreactor. The larger local CO₂ coverage derived from a higher CO₂ supply and aggregation enhances the C–C coupling, thereby generating more C2+. Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO₂ supply, for which the optimal gas inlet rate is 5–10 sccm.