Acquirement of the photocatalysts enabling stable and highly efficient water splitting hydrogen production remains an open challenge in the field of energy photocatalysis. Herein, Ni2P/γ-Ga2O3 nanosheets were reported as excellent...

Solar light-driven overall water splitting for hydrogen production is an ideal solution to climate warming and energy shortage issues. Obtaining a highly efficient and stable photocatalyst remains a major challenge at present. Herein, Ni x P/γ-Ga 2 O 3 nanosheets, which were synthesized from NiCl 2 , NaH 2 PO 2 , and home-made γ-Ga 2 O 3 nanosheets by the photodeposition method under 254 UV irradiation for 30 min, are found as a highly active and durable photocatalyst for pure water splitting into H 2 and O 2 without a sacrificial reagent. The H 2 production rate is as high as 5.5 mmol•g −1 •h −1 under 125 W high-pressure mercury lamp irradiation, which is 3.4 and 2.5 times higher than that on the pristine γ-Ga 2 O 3 nanosheets and Pt/γ-Ga 2 O 3 nanosheets, respectively, and is 2.0 times higher than that on the 0.5 wt % Ni 2 P/γ-Ga 2 O 3 reported previously. However, the O 2 evolution rate is much less than the H 2 evolution rate in the initial reaction stage. On prolonging the irradiation time, H 2 evolution declines, while O 2 evolution increases until it reaches its stoichiometric value corresponding to H 2 . The reason for the photocatalytic behavior of Ni x P/γ-Ga 2 O 3 is studied and the corresponding mechanism is suggested. The absent or low oxygen evolution in the initial reaction stage is because the dioxygen generated from water oxidation by the photogenerated holes is wholly or partially captured by the surface oxygen vacancies to form the surface peroxide bonds (−O−O−). Once the oxygen vacancies are eliminated by the photogenerated O 2 , the overall water splitting reaction would reach the steady state. Thereafter, H 2 production decreases from 5.5 to 2.0 mmol•g −1 •h −1 , but the O 2 evolution gradually approaches the corresponding stoichiometric value, especially for the photocatalyst treated with H 2 O 2 for 24 h.