Clustered tubular S-scheme ZnO/CdS heterojunctions for enhanced photocatalytic hydrogen production

Herein, a cluster-like ZnO/CdS nanotube heterojunction photocatalyst was prepared on an FTO conductive glass substrate by a two-step hydrothermal method. The photocatalytic performance and electron transfer mechanism of ZnO and ZnO/CdS composite structures were analyzed through comparing the hydrogen production efficiency of ZnO and ZnO/CdS. The photocatalytic hydrogen production activity of ZnO/CdS (molar ratio 1:1) achieved 7669 μmol/g/h with the AQE of 55.25 %. Unique clustered tubular structure, wider light absorption range and higher carrier transfer rate endowed the composite with marvellous photocatalytic hydrogen production activity. In addition, the measurement of hydroxyl radicals and ESR verified that the electron transfer mechanism followed the S-scheme, which improved the separation efficiency of electron-hole pairs. The residual ratio of catalysts on the FTO substrate remained above 99 % after two cycles, which was remarkably higher than that of the powder catalyst (63 %). This work provides terrific potential for high-efficient, low-cost and recyclable photocatalysts of hydrogen production in the future.