Z-scheme CdSe/ZnSe heterojunction for efficient photocatalytic hydrogen evolution

Construction heterojunction has been accepted as one of the most promising approaches to avoid charge recombination and extend light response range of a single photocatalyst, and achieve effective photocatalytic processes. Herein, a Z-scheme CdSe/ZnSe heterojunction was successfully synthesized via a simple mechanical mixing strategy. The results show that 3 wt% CdSe/ZnSe composite exhibits superior H2 evolution activity of 15.3 mmol·h−1·g−1 without cocatalyst in Na2S/Na2SO3 solution, which is 4.2 and 34.1 times higher than those of ZnSe and CdSe respectively under the same conditions. The apparent quantum efficiency (AQE) is 4.0% under 400 (±5) nm light irradiation. A Z-scheme charge transfer mechanism is established based on a series of trapping experiments and photochemical analyses, which is more beneficial for the charge separation as well as maintaining their relatively higher redox ability, leading to an excellent H2 evolution activity.