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The electroreduction of carbon monoxide (COER) to multi-carbon (C2+) products has been emerging as a promising strategy for generating value-added fuels and chemicals, yet the development of efficient catalysts for this process still remains a huge challenge. Herein, by means of density functional theory (DFT) computations, we explored the catalytic performance of several sub-nano Cu clusters (Cun, n = 1–6) supported by graphitic carbon nitride (Cun@g-C3N4) for the COER. Our results revealed that the COER catalytic activities of these candidates are greatly dependent on the sizes of the anchored Cu clusters, among which Cu3 clusters were predicted to be the best COER catalyst with a rather low limiting potential of −0.45 V for CH4 production due to their optimal binding strength with reaction intermediates. More interestingly, at high coverage, the adsorbed CO* species can couple with each other to form a key CO–CO–CO* species via a one-step concerted trimerization mechanism with a small activation barrier of 0.43 eV, which can be further hydrogenated to propene products with a small limiting potential of −0.40 V. Thus, the anchored Cu3 cluster on g-C3N4 is a quite promising catalyst for the COER with high efficiency to multi-carbon products, which offers useful guidance to further design sub-nano cluster-based catalysts for other electrochemical reactions. [ABSTRACT FROM AUTHOR]

The electrochemical carbon dioxide reduction reaction (CO2RR) holds great promise for mitigating CO2 emission and simultaneously generating high energy fuel. However, it remains a great challenge to reduce CO2 to C2 products due to the lack of highly efficient catalysts. Herein, by means of a particle swarm optimization search and comprehensive density functional theory (DFT) computations, we predicted a hitherto unknown Cu2N monolayer with planar hexacoordinate Cu and tetracoordinate N atoms as a CO2RR catalyst. Our results revealed that the Cu2N monolayer shows outstanding stability and intrinsic metallicity. Interestingly, the as-designed Cu2N monolayer exhibits superior CO2RR catalytic performance with a rather low limiting potential (−0.33 V), resulting in the formation of a C2H4 product with a small kinetic barrier (0.55 eV) for the coupling between *CH2 and a CO molecule. Strikingly, the N atoms within the Cu2N monolayer were revealed to be the CO2RR active sites due to their significant binding strength with the CO2RR species and their significant spin moments. Our findings not only propose a useful roadmap for the discovery of 2D hypercoordinate materials, but also provide cost-effective opportunities for advancing sustainable CO2 conversion. [ABSTRACT FROM AUTHOR]

Sustainable production of high-value carbon-based fuels and chemicals through electrochemical CO reduction (COR) under mild conditions is a promising alternative to the traditional Fischer–Tropsch process that requires high energy input and large-scale reactors. However, the COR process suffers from the low activity and poor selectivity of the currently employed electrocatalysts, greatly hampering its large-scale application. Herein, by means of comprehensive swarm-intelligence structure search and first-principles computations, we identify an ideal electrocatalyst for COR, i.e., a metallic Cu2B2 monolayer with planar heptacoordinate copper and planar pentacoordinate boron. Our results reveal that the predicted Cu2B2 monolayer exhibits superior thermal and dynamic stability and holds promise for experimental realization. More importantly, this catalyst could effectively reduce CO to ethanol through the "carbene" mechanism with a low limiting potential (−0.59 V) and a small barrier for C–C coupling (0.41 eV). Our work is the first report on the as-designed electrocatalyst with planar hypercoordinate motifs for CO reduction to C2 products, which not only widens the potential application of hypercoordinate 2D materials, but also opens up a new and promising avenue for converting abundant industrial CO to value-added ethanol. [ABSTRACT FROM AUTHOR]