Hydrogen production from iron sulphate photolysis using mark-5 cycle

ABSTRACT

Hydrogen production was carried out in a photochemical device in a Mark-5 cycle. The photolysis of iron sulphate solution was carried out in a close periodic system. The reaction mixture was 8.5 g iron sulphate compound (FeSO₄•7 H₂O), 2.5 g I₂ and 1.0 g HI in 100 mL water. Fifty millilitres of this solution was filled into a quartz reactor and connected to cycle system. The optimisation of hydrogen production was achieved by temperature, flow rate and radiation irradiation. The maximum hydrogen generated was 50.0 × 10¹⁶ molecules per minute at 120 °C temperature, 0.08 mL/sec. Pump speed, pressure 0.30 MPas, and Hg-vapour λmax = 365 nm. Eact. = 14.92 kC/mol caused bimolecular reactions to occur at low temperatures by photochemical action. Quantum yield of hydrogen depended on the absorbed of 0.5 × 10¹⁵ kvant/s. The energy of the quantum above T ≥ 100°C temperatures was φ ≥ 1. The dependence of the hydrogen generation rate (W) increased from 0.001 to 0.0038 × 10¹⁶ molecules/sec at 10-90 minutes, respectively.

KEYWORDS:

• Hydrogen production
• iron sulphate photolysis
• mark-5 cycle
• quantum yields
• mechanism of hydrogen production

Novelty

The demand for green energy, especially hydrogen, is growing continuously. Among many methods, water splitting under the influence of radiation is considered good, but it has several limitations such as being energy-intensive, costly, needing high infrastructure, moderate efficiency, and scale-up challenges. Therefore, efforts are made to produce hydrogen from ferrous sulphate solution in a home-made device by using a mark-5 combined cycle. The hydrogen was optimised by temperature, pump speed, radiation duration, and radiation wavelength. The reported method has high efficiency, integration with heat sources, scalability, flexibility to work, hydrogen purity, and need for low energy. Finally, 6.6 × 10¹¹ molecules of hydrogen are produced per minute. This is a very good amount and the method is inexpensive. The results are very important for producing green hydrogen at a large scale.

Acknowledgments

One of the authors (MAH) is thankful for funding from the Researchers Supporting Project Number (RSP2024R441), King Saud University, Riyadh, Saudi Arabia.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All the data are given in the manuscript.