Multiple Catalytic Reactions and Enhanced C2+ Products of CO 2 Reduction by Photocatalyst CuBi 2 O 4 : Reaction Intermediates and Mechanisms

With increasing atmospheric CO 2 , photocatalytic CO 2 reduction has emerged as a promising strategy to mitigate climate change. CuBi 2 O 4 , a semiconductor with a bandgap of 1.75 eV, shows broad visible absorption, making it a suitable candidate for photocatalytic applications. We used CuBi 2 O 4 as the photocatalyst and combined in situ Raman spectroscopy with density functional theory (DFT) calculations to investigate CO 2 reduction. Over 12 intermediates were assigned, and five new Raman bands of intermediates were identified. The Raman spectra showed a fast production rate, with downstream intermediates forming early and upstream species accumulating later. The intermediates O*CCO and O*CCHO arose from distinct pathways, confirming multiple C2 processes. DFT results revealed two active sites, O–Cu and O–Bi, both promoting C–C coupling. Significant amounts of CO (11.4 μmol g −1 h −1 ), H 2 (2.36 μmol g −1 h −1 ), CH 4 (0.85 μmol g −1 h −1 ), and a large fraction of C2+ products (C 2 H 4 /CH 4 ∼42%) were produced; hydrocarbons were promptly produced, and CO and H 2 were gradually produced and reached maximal amounts at later stages. DFT calculations show that CO 2 was converted to *CO via O*COH, and *CO, with high free energy, can easily desorb to form gas‐phase CO. This explains the high yield of CO product.