Abstract
We shall show in this presentation that carbonates (CO3 2-), typically regarded as being electrochemically-inert, can be directly electroreduced to formate. Through a combination of in situ Raman spectroscopy, HPLC, NMR spectroscopy, 13C and deuterium isotope-labelling, and DFT simulations, our study reveals that carbonate intermediates are adsorbed onto a copper electrode during CO2RR in KHCO3 electrolyte across potentials ranging from 0.2 to –1.0 V vs. RHE. These intermediates exhibit the capability to be reduced to formate at –0.4 V vs. RHE and at more negative potentials. Our observation is corroborated by the detection of formate resulting from the direct reduction of Cu2(CO3)(OH)2. We further conducted pulse electrolysis on a copper electrode immersed in N2-purged K2CO3 electrolyte, and show that the carbonate anions can first adsorb at –0.05 V vs. RHE and then be directly reduced to formate at –0.5 V vs. RHE with a Faradaic efficiency of 0.61 %. We elucidate the catalytically-active sites and propose a mechanism for the pulse-enabled reduction of carbonate to formate. These findings shed light on a direct route for the reduction of carbonates to a valuable product like formate and offer a potential approach for mitigating carbonate formation during CO2RR.
Published Version
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