A difunctional photocatalytic H2 evolution composite co-catalyst tailored by integration with earth-abundant material and ultralow amount of noble metal

[Display omitted] •An efficient composite co-catalyst (Pt / Mo2N) with ultralow amount of Pt is reported.•The composite co-catalyst (Pt / Mo2N) both considers the cost and efficiency.•Mo2N shows the large specific capacitance and stores electrons in photocatalysis.•The Pt mainly acts as the catalytic active center for proton reduction. Noble metals and earth-abundant materials are two kinds of co-catalysts in photocatalytic hydrogen production. However, the profound roles and catalytic mechanisms between them need to be clarified. Here, we report a composite co-catalyst by integration with Mo2N and Pt for efficient photocatalytic hydrogen production on CdS. Amazingly, the (Pt/Mo2N) composite with ultralow amount of Pt (0.006%) shows most efficient. The activity of optimum (Pt / Mo2N)/CdS reaches 1730 μmol/h/g, which are 6.2 times of Pt/CdS, 1.6 times of Mo2N/CdS and 7.2 times sole CdS, respectively. Electrochemical tests demonstrate Mo2N has large specific capacitance and mainly storing electrons, while Pt mainly acts as the catalytic active center. The different functions of Pt and Mo2N account for the superiority of (Pt/Mo2N). The fabrication strategy benefits the co-catalyst industrialization as both considerations to cost and efficiency.