Gold has long been one of the preferred electrode materials because of its chemical inertness. Yet gold at the nanoscale has been found to bind hydrogen and have much more catalytic activity. Two aspects of hydrogen on gold will be discussed. First, the product isotope effect for hydrogen evolution on polycrystalline gold — H2 vs. HD vs. D2 from mixed H2O/D2O solutions — has been examined using differential electrochemical mass spectrometry (DEMS) with ultrapure D2O. A substantial and potential-independent H/D isotope effect was observed, which has some mechanistic implications. In parallel, we are examining the chemical oxidation and reduction of aqueous colloidal gold nanocrystals, as monitored principally by the gold surface plasmon resonance (SPR). For example, the Au nanocrystals are reduced with borohydrides and then re-oxidized by the nitroxyl radical TEMPO. The gold colloids change color when exposed to H2 gas, a process that is reversible in a number of ways. The chemical nature of these reactions, all of which likely fall under the umbrella of proton coupled electron transfer (PCET), will be discussed.

Adventures in proton-coupled electron transfer at gold-solution interfaces

ACS Spring 2022

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