CO
2 electroreduction offers a route to net-zero-emission production of C
2H
4—the most-produced organic compound. However, the formation of carbonate in this process causes loss of CO
CO
2 electroreduction offers a route to net-zero-emission production of C
2H
4—the most-produced organic compound. However, the formation of carbonate in this process causes loss of CO
2 and a severe energy consumption/production penalty. Dividing the CO
2-to-C
2H
4 process into two cascading steps—CO
2 reduction to CO in a solid-oxide electrolysis cell (SOEC) and CO reduction to C
2H
4 in a membrane electrode assembly (MEA) electrolyser—would enable carbonate-free C
2H
4 electroproduction. However, this cascade approach requires CO-to-C
2H
4 with energy efficiency well beyond demonstrations to date. Here, we present a layered catalyst structure composed of a metallic Cu, N-tolyl-tetrahydro-bipyridine, and SSC ionomer that enables efficient CO-to-C
2H
4 in a MEA electrolyser. In the full SOEC-MEA cascade approach, we achieve CO
2-to-C
2H
4 with no loss of CO
2 to carbonate and a total energy requirement of ~138 GJ (ton C
2H
4)
−1, representing a ~48% reduction in energy intensity compared with the direct route.
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