Efficient catalytic hydrogenation of nitroarenes to anilines with molecular hydrogen at room temperature is still a challenge. In this study, this transformation was achieved by using a photocatalyst of SiC-supported segregated Pd and Au nanoparticles. Under visible-light irradiation, the nitrobenzene hydrogenation reached a turnover frequency as high as 1715 h at 25 °C and 0.1 MPa of H pressure. This exceptional catalytic activity is attributed to a synergistic effect of Pd and Au nanoparticles on the semiconducting SiC, which is different from the known electronic or ensemble effects in Pd-Au catalysts. This kind of synergism originates from the plasmonic electron injection of Au and the Mott-Schottky contact at the interface between Pd and SiC. This three-component system changes the electronic structures of the SiC surface and produces more active sites to accommodate the active hydrogen that spills over from the surface of Pd. These active hydrogen species have weaker interactions with the SiC surface and thus are more mobile than on an inert support, resulting in an ease in reacting with the N═O bonds in nitrobenzene absorbed on SiC to produce aniline.