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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.

CO2 reduction is of significant interest for the production of nonfossil fuels. The reactivity of eight Cu foams with substantially different morphologies was comprehensively investigated by analysis of the product spectrum and in situ electrochemical spectroscopies (X‐ray absorption near edge structure, extended X‐ray absorption fine structure, X‐ray photoelectron spectroscopy, and Raman spectroscopy). The approach provided new insight into the reactivity determinants: The morphology, stable Cu oxide phases, and *CO poisoning of the H2 formation reaction are not decisive; the electrochemically active surface area influences the reactivity trends; macroscopic diffusion limits the proton supply, resulting in pronounced alkalization at the CuCat surfaces (operando Raman spectroscopy). H2 and CH4 formation was suppressed by macroscopic buffer alkalization, whereas CO and C2H4 formation still proceeded through a largely pH‐independent mechanism. C2H4 was formed from two CO precursor species, namely adsorbed *CO and dissolved CO present in the foam cavities. Inner values matter! Eight Cu foams with substantially different morphologies were investigated by analyzing the product spectrum. Electrochemical in situ spectroscopies revealed that the reactivity was controlled by internal surface area. [ABSTRACT FROM AUTHOR]

Selective electrochemical reduction of CO 2 is an emerging field which needs more active and stable catalysts for its practicability. In this work, we have studied the influence of Ag metal incorporation into Cu dendritic structures on the product distribution and selectivity of CO 2 electroreduction. Bimetallic AgCu foams prepared by hydrogen bubble templated electrodeposition shift the potentials of CO production to more positive values compared to bulk silver. The presence of Ag during the electrodeposition significantly changed the size and the shape of the dendrites in the pore walls of AgCu foams compared to Cu foam. The CO adsorption characteristics are studied by operando Raman spectroscopy. In the presence of Ag, the maximum CO adsorption is observed at a more positive potential. As a result, an improved selectivity for CO is obtained for AgCu foam catalysts at lower overpotentials compared to Cu foam catalyst, evidencing a synergistic effect between the bimetallic components. We were successful in increasing the CO mass activity with respect to the total Ag amount. AgCu foams are found to retain the CO selectivity during long-term operation, and with their easily scalable electrodeposition synthesis they possess high potential for industrial application.

CO 2 reduction is of significant interest for the production of nonfossil fuels. The reactivity of eight Cu foams with substantially different morphologies was comprehensively investigated by analysis of the product spectrum and in situ electrochemical spectroscopies (X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray photoelectron spectroscopy, and Raman spectroscopy). The approach provided new insight into the reactivity determinants: The morphology, stable Cu oxide phases, and *CO poisoning of the H 2 formation reaction are not decisive; the electrochemically active surface area influences the reactivity trends; macroscopic diffusion limits the proton supply, resulting in pronounced alkalization at the CuCat surfaces (operando Raman spectroscopy). H 2 and CH 4 formation was suppressed by macroscopic buffer alkalization, whereas CO and C 2 H 4 formation still proceeded through a largely pH-independent mechanism. C 2 H 4 was formed from two CO precursor species, namely adsorbed *CO and dissolved CO present in the foam cavities., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)