Biomolecule-Incorporated CdS Nanocomposites as Highly Active Photocatalysts for Hydrogen Production from Water

Cadmium sulfide (CdS) is a promising material for photocatalytic water splitting to produce renewable solar hydrogen. However, its low activity and susceptibility to photocorrosion hinder its practical use. To address these issues, we introduce biomolecules like phenylalanine, histidine, tyrosine, tryptophan, and lysine to the CdS compound. Among these, CdS nanoparticles with phenylalanine exhibit the highest hydrogen gas production, generating 580 μmol h^–1of hydrogen under visible light exposure, which is 22 times higher than that of the CdS-only sample. Furthermore, we optimize the amount of phenylalanine incorporated into the CdS photocatalyst as well as the quantity of photocatalyst used in laboratory-scale experiments. Our findings indicate that using 20 mg of CdS material in 40 mL of reaction solution maximizes the hydrogen production rate, achieving an impressive 796 μmol h^–1. CdS modified with phenylalanine exhibits an excellent photon conversion efficiency, reaching a remarkable apparent quantum yield of 86%. Our observation reveals that the biomolecules (amino acids) are embedded within the CdS crystal structure, which may interact with the photogenerated holes, thus enhancing the photocatalytic efficiency.