Anisotropic Cathodic Corrosion of Gold Electrodes in the Absence and Presence of Carbon Monoxide

Abstract

In this work, we investigate gold surface dissolution under cathodic potentials as a function of crystal orientation using cyclic voltammetry, scanning electron microscopy, and atomic force microscopy to determine to what extent cathodic corrosion is anisotropic in nature. Additional experiments were performed to gain insights into the effect of the presence of CO on cathodic corrosion. Carbon monoxide experiments were conducted to investigate the effect of more realistic reaction conditions on cathodic corrosion as they might be found in gold-driven CO2 electrolyzers, although the effects of the presence of CO2 (reactant) and carbonate salts (typically present in the reaction medium) were excluded from this study. It was found that cathodic corrosion of gold is strongly anisotropic, with stepped surfaces and the {110} plane being most susceptible to dissolution, whereas the {111} and {100} planes were much more resilient to dissolution. On these more stable surfaces, nanocrystallite growth was observed instead, which we hypothesize originates from redeposition of the gold that dissolves from the more corrosive, more open, and/or defective facets. Finally, the presence of carbon monoxide was found to slightly enhance the rate of surface change, as evidenced by increases in charge in cyclic voltammograms after corrosion and an earlier onset of crystallite growth on the {111} and {100} planes, which we ascribe to enhanced gold mobility due to the strong bond formed between CO and gold in alkaline media.