Photochemical construction of the ZnCdS/PO/FeCoNiPi-MnO composite for efficient tandem application of photocatalytic partial water splitting and overall water splitting

Developing a sacrificial agent-free Zn1-xCdxS-based photocatalyst for efficient photocatalytic overall water splitting (POWS) is economical and eco-friendly but a challenging task. Herein, we synthesize a phosphorus (PO) protection layer and non-precious FexCoyNizP and MnOa cocatalysts on Zn0.4Cd0.6S by a safe and energy-saving two-step photochemical strategy. The prepared Zn0.4Cd0.6S/PO/Fe(x)Co(y)Ni(z)Pi-MnOa photocatalyst displays average hydrogen and oxygen evolution rates of similar to 1.14 mmol h(-1) g(-1) and similar to 0.54 mmol h(-1) g(-1) in POWS, respectively, where FexCoyNizP and MnOa act as the photogenerated electron and hole acceptors and provide the active sites for the two reactions. The superior POWS performance was maintained for 12 hours without any obvious attenuation. Moreover, photocatalytic partial water splitting (PPWS) is induced by the oxidation of NaH2PO2 during the photochemical synthesis process, yielding hydrogen evolution rates of 7.22 mmol h(-1) g(-1) and 5.90 mmol h(-1) g(-1), respectively. By integrating the two-step photochemical synthesis and POWS process (PPWS -> PPWS -> POWS), we obtain a total H-2 yield of about 4.85 mmol under 17 h visible light irradiation, which corresponds to an average H-2 evolution rate of 0.29 mmol h(-1). This work develops a safe and energy-saving photochemical synthesis strategy for Zn1-xCdxS-based photocatalysts, which not only exhibits excellent POWS performance but opens an avenue for the tandem application of PPWS and POWS to achieve a high H-2 total yield for solar-energy conversion.