Controllable photochemical synthesis of amorphous Ni(OH)2 as hydrogen production cocatalyst using inorganic phosphorous acid as sacrificial agent

Abstract Loading of cocatalysts can effectively inhibit the recombination of photogenerated carriers in photocatalysts and greatly improve the photocatalytic hydrogen production rate. Cocatalysts can be deposited at the outlet points of electrons using a photochemical method, which is beneficial for the following photocatalytic hydrogen production reaction. H2PO2– has been used in the photochemical reduction of transition metals because of its special properties. However, the particles formed in the presence of H2PO2–are very large and highly crystalline, which may inhibit the activity of photocatalysts. In this study, we designed a new method for synthesizing photocatalysts by photodeposition using some other phosphates, aiming to prepare controllable weakly crystalline and small-size cocatalysts to improve the hydrogen production activity. The cocatalyst prepared using H2PO3– as an inorganic sacrificial agent has an amorphous structure and an average size of about 10 nm. The optimal photocatalytic hydrogen production rate of the obtained Ni(OH)2/g-C3N4 (4.36 wt%) is 13707.86 μmol·g−1·h−1, which is even higher than the activity of Pt-4.36 wt%/g-C3N4 (11210.93 μmol·g−1·h−1). Mechanistic studies show that loading of Ni(OH)2 can efficiently accelerate the separation and transfer efficiency of photogenerated charge carriers.