The electrocatalytic CO2 recycling into high added-value products has been attracting wide attention for years. Co-feeding CO2/CO and using tandem catalysts now are well-recognized strategies to facilitate C–C coupling and the production of C2+ products. In a pioneering paper published in 2019 in Nature Nanotechnology, Wang et al. presented initial evidences about the dominant contribution of the *CO (from CO)–*CO (from CO2) cross-coupling pathway over a wide electrode potential range and designed tandem catalysts that realized enhanced ethylene production rate (Nat. Nanotechnol. 14, 1063–1070; 2019).
The mechanistic understanding of the catalytic systems nowadays greatly relies on in situ and operando characterizations. However, designing an in situ and operando experimental setup that recreates realistic reaction conditions is sometime a challenge in itself. “It took a lot of time building up the in situ and operando set-ups and optimizing the experiments. We spent great efforts on the kinetic isotope-labelling experiments — performed an operando differential electrochemical mass spectrometry capillary flow cell with millisecond time resolution, but in the end the hard work paid off,” says Xingli Wang from the Technical University Berlin, and first author of the paper. In CO2/CO co-feed conditions they found cross-coupled C2H4 from 13CO and 12CO2 sources (pictured). This mechanistic understanding of the catalytic process guides the design of the tandem catalysts using a non-metallic component to reduce CO2 to CO, creating a co-feed condition for downstream copper oxide nanoparticles to form C2H4 with much more enhanced rate.
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