Insights from Operando and Identical Location (IL) Techniques on the Activation of Electrocatalysts for the Conversion of CO2: A Mini-Review

In this mini-review we compare two prototypical metal foam electrocatalysts applied to the transformation of CO2 into value-added products (e.g. alcohols on Cu foams, formate Bi foams). A substantial improvement in catalyst performance is typically achieved through thermal annealing air as-deposited materials, followed by electro-reduction pre-formed oxidic precursors prior or during actual electrolysis. Utilizing highly insightful and sensitive complementary operando analytical techniques (XAS, XRD, Raman spectroscopy) demonstrate that pre-activation process entirely accomplished case oxidized foams formation hydrocarbons from CO2. The actually active therefore metallic derived precursor means its oxide electroreduction. Conversely, their form, Cu-based catalysts are completely inactive towards reduction reaction (denoted ec-CO2RR). Oxidized can be regarded as an excellent counter example above-mentioned both thermally ec-CO2RR (formate production). Indeed, spectroscopy reveals electrolysis occurs upon embedment Bi2O3 precursor, which itself undergoes partial sub-carbonate phase. potential-dependent transition sub-carbonate/oxides corresponding dictates characteristic changes pathway. Identical location (IL) microscopic inspection e.g. scanning electron microscopy, demonstrates morphological alterations nm length scale material surface consequence potential-driven foam. morphology a mesoscopic (macroporosity) remains, contrast, fully unaffected these phase transitions.