Influence of Cocatalysts (Ni, Co, and Cu) and Synthesis Method on the Photocatalytic Activity of Exfoliated Graphitic Carbon Nitride for Hydrogen Production.

Exfoliated graphitic carbon nitride (ex-g-CN) was synthesized and loaded with non-noble metals (Ni, Cu, and Co). The synthesized catalysts were tested for hydrogen production using a 300-W Xe lamp equipped with a 395 nm cutoff filter. A noncommercial double-walled quartz-glass reactor irradiated from the side was used with a 1 g/L catalyst in 20 mL of a 10 vol% triethanolamine aqueous solution. For preliminary screening, the metal-loaded ex-g-CN was synthesized using the incipient wetness impregnation method. The highest hydrogen production was observed on the Ni-loaded ex-g-CN, which was selected to assess the impact of the synthesis method on hydrogen production. Ni-loaded ex-g-CN was synthesized using different synthesis methods: incipient wetness impregnation, colloidal deposition, and precipitation deposition. The catalysts were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption using the Brunauer-Emmett-Teller method, and transmission electron microscopy. The Ni-loaded ex-g-CN synthesized using the colloidal method performed best with a hydrogen production rate of 43.6 µmol h-1 g-1. By contrast, the catalysts synthesized using the impregnation and precipitation methods were less active, with 28.2 and 10.1 µmol h-1 g-1, respectively. The hydrogen production performance of the suspended catalyst (440 µmol m-2 g-1) showed to be superior to that of the corresponding immobilized catalyst (236 µmol m-2 g-1).

Selective Cocatalyst Deposition on ZnTiO3-x Ny Hollow Nanospheres with Efficient Charge Separation for Solar-Driven Overall Water Splitting.

Pt and RhOx cocatalysts are selectively deposited at inner and outer surface of ZnTiO3-x Ny hollow nanospheres, respectively. The resulting photocatalytic systems exhibit promising activity for photocatalytic overall water splitting with stoichiometric H2 /O2 ratio under simulated solar insolation. Selective deposition of Pt and RhOx cocatalysts at different surfaces not only mitigates back reactions of the products but also induces strong potential gradient within nanospheres that promotes efficient dissociation and fast migration of photocarriers to the surface.