Fig. 2

¹³CO₂ isotopolog confirmation of CO₂RR. a Total ion chromatogram (TIC) of the gaseous products from a 240 h long Au NP-photocatalyzed ¹³CO₂RR in 5 mol% EMIM-BF₄ solution under CW irradiation of 532 nm light (1 W cm^–2). Peaks in the TIC appearing at retention times of 4.6 min and 8.2 min correspond to ¹³CH₄ and ¹³C₂H₂. The basis for this assignment is provided in Supplementary Fig. 22. b Mass fragmentation pattern (red bars) acquired at a retention time of 4.6 min of the TIC shown in a. For comparison, a reference fragmentation pattern (gray bars) of ¹²CH₄ from the National Institute of Standards and Technology (NIST) Chemistry WebBook is shown. Fragments at m/z = 14 and 18 in the experimental pattern were suppressed to remove the mass peaks contributed by N₂ and moisture, respectively. c Mass fragmentation pattern (blue bars) acquired at a retention time of 8.2 min of the TIC shown in a. For comparison, a reference fragmentation pattern (gray bars) of ¹²C₂H₂ from the NIST Chemistry WebBook is shown. The fragment at m/z = 28 in the experimental pattern has relatively high abundance as compared with that of the reference fragmentation pattern due to the contribution of N₂ from the atmosphere. Relative abundances in b and c were obtained from the measured abundances shown in Supplementary Fig. 21a, b, respectively. It is noteworthy that ¹³C₂H₄ was not resolved by GC-MS due to the likely overlap of the ¹³C₂H₄ peak with the broad, intense ¹³CO₂ peak in the TIC (Supplementary Fig. 22b)