Electrochemical Reduction of CO2 to Formate on Glacial Acetic Acid-Refluxed Pd Nanoclusters

The electrochemical reduction of CO2(CO2ER) to formate on Pd has attracted the broad interest in the chemical energy storage/conversion systems. However, this reaction is commonly constrained to a narrow potential range (positive to -0.25 V (vs RHE)) and low reactivity due to CO poisoning on the Pd surface. Here, the Pd/carbon catalyst was refluxed in glacial acid (A-Pd/XC72) to enhance the CO tolerance and the formate forming activity of Pd. The results demonstrate that the faradaic efficiency (F.E.) and charges for formate formation are over 95% and 60 coulombs over 1 h of electrolysis at -0.3 V (vs RHE) in the CO2-saturated 0.5 M KHCO(3)solution, which are 4 times as high as original Pd/XC72. The F.E. of formate formation remains around 80% when the applied potential is shifted to -0.5 V (vs RHE). Bothi-tand cyclic voltammetric (CV) analyses indicate the low rate of CO self-poisoning on A-Pd/XC72. The UV-vis spectra recording the surface change of Pd NPs in the glacial acetic acid suggest the adsorption of acetate species onto the surface of Pd, which are decomposed into carbonaceous species after heating, enhancing the CO2ER selectivity toward the formate formation.