Membrane electrode assembly (MEA) cells incorporating Cu catalysts are effective for generating C2+ chemicals via the CO2 reduction reaction (CO2RR). However, the impact of MEA configuration on the inevitable reconstruction of Cu catalysts during CO2RR remains underexplored, despite its considerable potential to affect CO2RR efficacy. Herein, we demonstrate that MEA cells prompt a unique reconstruction of Cu, in contrast to H-type cells, which subsequently influences CO2RR outcomes. Utilizing three Cu-based catalysts, specifically engineered with different nanostructures, we identify contrasting selectivity trends in the production of C2+ chemicals between H-type and MEA cells. Operando X-ray absorption spectroscopy, alongside ex-situ analyses in both cell types, indicates that MEA cells facilitate the reduction of Cu2O, resulting in altered Cu surfaces compared to those in H-type cells. Time-resolved CO2RR studies, supported by Operando analysis, further highlight that significant Cu reconstruction within MEA cells is a primary factor leading to the deactivation of CO2RR into C2+ chemicals.

Electrochemical CO2 reduction (CO2R) is an attractive option for storing renewable electricity and for the sustainable production of valuable chemicals and fuels. In this roadmap, we review recent progress in fundamental understanding, catalyst development, and in engineering and scale-up. We discuss the outstanding challenges towards commercialization of electrochemical CO2R technology: energy efficiencies, selectivities, low current densities, and stability. We highlight the opportunities in establishing rigorous standards for benchmarking performance, advances in in operando characterization, the discovery of new materials towards high value products, the investigation of phenomena across multiple-length scales and the application of data science towards doing so. We hope that this collective perspective sparks new research activities that ultimately bring us a step closer towards establishing a low- or zero-emission carbon cycle.