Influence of Sulfur Doping of Crystalline Carbon Nitride on Photocatalytic Hydrogen Evolution from Alcohol–Aqueous Solutions Under Visible Light

The influence of sulfur on the morphology, spectral, and photocatalytic properties of bulk (S-g-C₃N₄) and crystalline carbon nitride (S-CGCN), obtained by the pyrolysis of melamine–S₈ mixtures and additional thermal treatment of S-g-C₃N₄ in the eutectic melt of KCl and LiCl salts, has been investigated. It is shown that crystalline carbon nitride obtained in the presence of 5 wt.% of S₈ (5S-CGCN) demonstrate the highest photocatalytic activity in the hydrogen evolution process from water–ethanol solutions under the effect of visible light. The effective quantum yield of H₂ formation with the participation of 5S-CGCN and metal co-catalysts (palladium and gold) is Φ ≈ 100% at λ = 405 nm, which is almost twice as much as with the participation of unmodified CGCN. The high activity of 5S-CGCN can be associated with more intensive absorption of light, better separation of photogenerated charges, and suppression of their recombination.