Au and Pt co-loaded g-C3N4 nanosheets for enhanced photocatalytic hydrogen production under visible light irradiation

•The effect of loading order on the chemical state of Au and Pt was investigated.•The effect of Au and Pt co-loading on photocatalytic activity of g-C3N4 was study.•The photoluminescence properties of the as-prepared samples were investigated.•The photoelectronic response of the products was characterized.•The role of SPR effect of Au on water splitting into hydrogen was discussed. Au and Pt have been considered as the active co-catalysts for the enhanced photocatalytic activity of carbon nitride. However, the effects of Au and Pt co-loading on the surface chemical states and activity of carbon nitride were rarely discussed. In this work, a series of carbon nitride samples with Au and Pt loading have been successfully prepared by a traditional photodeposition method. The as-prepared samples have been characterized in detail. The activities of the samples were evaluated by water splitting into hydrogen under visible light irradiation. Results show that the integrity of characteristic structure of carbon nitride is retained before and after deposited Au and Pt. Interestingly, when Pt is firstly loaded on the surface of carbon nitride, Pt species are in the form of PtO with small particle size. While if Pt is loaded on the surface of Au/carbon nitride, the Pt nanoparticles (NPs) are metallic Pt NPs with relatively large particle size. For Au, it is insensitive to the loading order. Among all Au deposited samples, Au species are in the form of metallic Au. Furthermore, the activities of the Au and Pt co-loaded samples exhibited much higher than those of single co-catalyst deposited samples and pure carbon nitride. The dual co-catalysts in the form of metallic state are more active to increase the performance of water splitting over carbon nitride. The enhanced activity of carbon nitride by co-deposited Au and Pt could be well explained by the photoabsorption performance and the separation of photogenerated electron and holes.