Thermodynamic analysis of solar-based photocatalytic hydrogen sulphide dissociation for hydrogen production

• Performance limits of photocatalytic hydrogen sulfide splitting.
• Consideration of solar spectrum as input.
• Effect of temperature and intensity on energy and exergy efficiencies.
• Effect of quantum efficiency on the exergy efficiency.
• Effect of catalyst band gap on the exergy efficiency.

The dissociation of gaseous hydrogen sulphide (H2S) into its components is an energy intensive process. The process is studied in this paper with respect to the thermodynamic limits. The band gap of the catalyst and the nature of the solar radiation limit the proportion of incoming radiation that may be used for the reaction. The intensity of the incoming radiation and the reactor temperature are varied and the performance is studied. The exergy efficiency is determined as a function of the quantum efficiency of the photochemical process, and the catalyst band gap. It is shown that an optimum case exergy efficiency of up to 28% can be achieved for the process. With the current status of technology, an exergy efficiency value in the region of 0.4–1% is calculated, with a short-term improvement potential of up to 10%. Hydrogen sulfide has high energy content, but is not widely used due to its impact on environmental pollution. The proposed process in this paper is attractive as it allows that energy to be utilized, while degrading the highly toxic gas into less harmful products.