Direct splitting of H2S into H2 and S on CdS-based photocatalyst under visible light irradiation

The conversion of H2S into H-2 and S (H2S -> H-2 + S) is beneficial from both environmental and energy standpoints. Here we report that H2S can be splitted stoichiometrically into hydrogen and sulfur on CdS-based photocatalysts under visible light irradiation using ethanolamine as a H2S solvent and reaction media at room temperature. Raman spectra showed that the produced sulfur existed as S-4(2-) and S-6(2-) after photocatalytic reaction. The hydroxyls of the reaction media were found to be crucial for the hydrogen production, and the rate-determining step (RDS) of photocatalytic splitting H2S in diethanolamine is discussed. Electrochemical evaluation showed that the potential of H2S splitting in ethanolamine was greatly lowered and the photogenerated electrons could be fully used to reduce protons for hydrogen production. A free-radical-related one-electron electrochemical oxidation process on platinum electrode is suggested. This work demonstrates the possibility of the direct splitting H2S into S and H-2 via photocatalysis. (C) 2008 Elsevier Inc. All rights reserved.