Roles of cocatalysts in Pt-PdS/CdS with exceptionally high quantum efficiency for photocatalytic hydrogen production

► The essentials of the exceptionally high quantum efficiency (93%) were investigated. ► The mechanism of photocatalytic course was studied by in situ measurement. ► PdS and Pt act as the oxidation and reduction co-catalysts, respectively. ► The recombination of photo-generated charges is suppressed by co-catalysts. ► Atomic junctions between the co-catalysts and CdS are formed.