Four possible pathways of H2S decomposition into hydrogen and elemental sulfur are considered. In the thermal reversible process, H2S dissociation results in the formation of diatomic both hydrogen and sulfur in the singlet state according to the rule of spin conservation: (i) On the surface of sulfide catalysts, irreversible H2S splitting proceeds at low temperature through the stage of disulfane, H2S2 formation as a key surface intermediate, followed by its decomposition due to release of hydrogen into the gas phase and recombination of the adsorbed singlet sulfur into cyclooctasulfur: (ii) On metal catalysts, irreversible H2S decomposition occurs at low temperature through the stage of H2S dissociation into the adsorbed atomic surface species resulted in the formation of both diatomic reaction products in the ground electronic state -the singlet hydrogen and the triplet diatomic sulfur: (iii) The reactions (ii) and (iii) are considered to be realized under the principles of biological thermodynamics, in the absence of catalyst both reactions are thermodynamically prohibited in the gas phase. The mechanism of H2S assimilation by sulfur bacteria is suggested to occur in the processes of chemosynthesis resulted in the formation of colorless sulfur globules and activated hydrogen: (iv) Similar to the bacterial process, the hydrogen production from H2S is realized with the efficiency of 99.6% on metal catalysts immersed into the liquid which is capable well-dissolving H2S.
AN, S. (2017). The Reaction Mechanisms of H2S Decomposition into Hydrogen and Sulfur: Application of Classical and Biological Thermodynamics. Journal of Thermodynamics & Catalysis, 08(02). https://doi.org/10.4172/2157-7544.1000186