Effects of supports (Co3O4, CeO2, NiO) in the gold-catalyzed aqueous phase oxidation of ethanol (EtOH) to acetic acid (AcOH) were examined. ATR-IR spectroscopy under working conditions of the catalysts uncovered on gold particles bidentate ethoxy, and on supports monodentate ethoxy species, multi-layered ethanol, and acetate. Preferential formation of bidentate ethoxy species and adsorbed EtOH were identified as key factors for high activity and selectivity to AcOH. These requirements were best matched with Au/Co3O4. On NiO, monodentate ethoxy species on the support deteriorated the catalytic performance due to consecutive esterification of AcOH and/or acetate species with EtOH producing undesirable ethyl acetate.