The electrochemical CO2 reduction reaction (CO2RR) catalyzed by metal nanoparticles (NPs) is a promising approach to carbon neutral and energy sustainability. Using monodisperse NPs of Au and nanowires of Cu as examples, we show that selective electrochemical reduction of CO2 can be achieved via Au-Cu catalysis synergy.  When Au NPs are anchored on Cu nanowires by bipyridine (bipy), the composite Au-bipy-Cu shows a much improved catalysis to convert CO2 to hydrocarbon products with the total Faradaic efficiency (FE) reaching 90.6% at -0.9 V. The reduction yields C2-products of ethylene, acetate and ethanal with a combined FE of 51.3%. We further extended our studies to ferromagnetic hexagonal-close-packed (hcp) Co nanosheets (NSs), and found that in the reduction potentials tested from −0.2 to −1.0 V (vs RHE) in 0.5 M KHCO3 solution, the reduction yields ethanal as a major product and ethanol/methanol as minor products. At −0.4 V, the FE for ethanal reaches 60% with current density of 5.1 mA/cm2 and mass activity of 3.4 A/g (total FE for ethanal/ethanol/methanol is 82%). Density functional theory (DFT) calculations suggest that this high CO2RR selectivity to ethanal on the hcp Co surface is attributed to the unique intralayer electron transfer, which not only promotes [OC−CO]* coupling but also suppresses the complete hydrogenation of the coupling intermediates, leading to highly selective formation of ethanal (CH3CHO).

New strategies to the design of nanocatalysts for selective CO2 reduction

ACS Spring 2022

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