Exchange of CO 2 with CO as Reactant Switches Selectivity in Photoreduction on Co−ZrO 2 from C 1–3 Paraffin to Small Olefins

Photocatalytic reduction of CO 2 into C 2,3 hydrocarbons completes a C‐neutral cycle. The reaction pathways of photocatalytic generation of C 2,3 paraffin and C 2 H 4 from CO 2 are mostly unclear. Herein, a Co 0 −ZrO 2 photocatalyst converted CO 2 into C 1–3 paraffin, while selectively converting CO into C 2 H 4 and C 3 H 6 (6.0±0.6 μmol h −1 g cat −1 , 70 mol %) only under UV/Visible light. The photocatalytic cycle was conducted under 13 CO and H 2 , with subsequent evacuation and flushing with CO. This iterative process led to an increase in the population of C 2 H 4 and C 3 H 6 up to 61–87 mol %, attributed to the accumulation of CH 2 species at the interface between Co 0 nanoparticles and the ZrO 2 surface. CO 2 adsorbed onto the O vacancies of the ZrO 2 surface, with resulting COH species undergoing hydrogenation on the Co 0 surface to yield C 1–3 paraffin using either H 2 or H 2 O (g, l) as the reductant. In contrast, CO adsorbed on the Co 0 surface, converted to HCOH species, and then split into CH and OH species at the Co and O vacancy sites on ZrO 2 , respectively. This comprehensive study elucidates intricate photocatalytic pathways governing the transformation of CO 2 into paraffin and CO to olefins.