ИСТИНА

To be economically profitable, the electrocatalytic carbon dioxide (CO2) conversion should meet various criteria such as (i) high CO2 conversion rates, (ii) a high product selectivity, (iii) a high energy efficiency, and (iv) a high catalyst stability.[1] The crucial step in the CO2 reduction reaction (CO2RR) involves the initial formation of CO2·− radical anions as key intermediates, which, however, occurs only at very high overpotentials [2] thus giving rise to a low energy efficiency of the overall process. Therefore, as a primary step, one needs to identify electrocatalytic systems with a minimal possible overpotential of CO2RR. Efforts have been devoted to the development of superior nanostructured electrocatalysts and to the tailored design of appropriate electrolyte systems. Nanostructured metal catalysts (such as Ag, Cu, Au, Pd, Zn) have been shown to decrease the CO2RR overpotential due to the presence of more active surface sites [3]. A particular attention was paid to nanostructured Ag catalysts, as Ag demonstrates high selectivity towards the formation of carbon monoxide (CO) in CO2RR. Furthermore, the use of room-temperature ionic liquids (ILs) can also decrease the CO2RR overpotential.[4] In this work, we employ a novel type of nanostructured Ag electrocatalyst for the CO2 electroreduction in 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]). The Ag catalyst is prepared by galvanostatic electrodeposition of Ag at high current density. It represents a Ag foam, consisting of nanorods with diameters in the range of 50 to 100 nm (Fig. 1, left). This electrocatalyst significantly decreases the CO2RR overpotential as compared to a Ag foil electrode (Fig. 1, right panel) and provides highly selective CO production in a rather broad potential window of 0.4 V in [Bmim][BF4]. The stability of the IL and the Ag catalyst during extended CO2 electrolysis was examined by NMR analysis and identical location scanning electron microscopy (IL-SEM), respectively.