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[Display omitted] • Photocatalytic performance of plasma-treated Au catalyst depends on oxide supports. • Plasma-treatment leads to distinct interactions between oxide supports and Au. • Strong interaction between CeO 2 and Au enables high intrinsic activity of Au/CeO 2. • Moderate interaction between TiO 2 and Au favors forming Au-TiO 2 interfacial sites. • Au-TiO 2 interface exhibits low Schottky barrier height for hot-electron transfer. Supported Au nanocatalysts are highly attractive plasmonic nanostructures for visible light (VL) photocatalysis due to their significant promise in direct conversion of solar to chemical energy. A promising strategy to prepare high-performance supported plasmonic Au nanocatalysts is treating the catalysts with plasma, where the support holds the key to constructing active Au-support interfaces by interacting with Au nanoparticles. Herein the role of oxide supports in constructing plasma-treated plasmonic Au nanocatalysts for VL photocatalytic oxidation of CO is studied by comparing effect of plasma treatment on typical oxides of TiO 2 , CeO 2 and Al 2 O 3 supported Au nanocatalysts. After O 2 plasma treatment, CeO 2 supported Au nanocatalyst obtains the highest intrinsic catalytic activity due to its high dispersion of Au nanoparticles induced by strong interaction between CeO 2 and Au and strong oxygen activation ability. The O 2 plasma treatment enables TiO 2 supported Au nanocatalyst to exhibit the largest enhancement in catalytic activity under VL irradiation, which originates from the favorable hot-electron transfer process. This process is not only attributed to the strong surface plasmon resonance of Au nanoparticles and large numbers of Au-TiO 2 interfacial sites that result from moderate interaction between TiO 2 and Au, but also depends on the low Schottky barrier height at Au-TiO 2 interface due to the small work function difference between TiO 2 and metallic Au. This investigation deepens the understanding of the role of oxide supports in constructing plasma-treated supported Au nanocatalysts, and can be instructive for the design and optimization of plasmonic Au nanocatalysts for VL photocatalytic reactions. [ABSTRACT FROM AUTHOR]