Size effect-tuned water gas shift reaction activity and pathway on ceria supported platinum catalysts

•The Pt/CeO2 catalysts for water-gas shift reaction have a prominent size effect.•The active sites of Pt/CeO2 were uncovered as Ptδ+-OV-Ce3+ species.•The carboxyl route was preferred rather than the formate one.•New insights on the interfacial electronic and geometric effects in Pt/CeO2 for WGSR.