First solar-based process revealed to safely, efficiently split water

January 8, 2020 |

From Israel, word comes from researchers at the Technion – Israel Institute of Technology and the University of Porto in Portugal who have developed a prototype system for efficient and safe production of hydrogen using only solar energy. 

The details are here in Joule.

The technology breakthrough

The system contains a tandem cell solar device, which enables more efficient utilization of the light spectrum. Some of the sun’s radiation is absorbed in the upper layer, which is made of semi-transparent iron oxide. The radiation that is not absorbed in this layer passes through it and is subsequently absorbed by a photovoltaic cell. Together, the two layers of the system provide the energy needed to decompose the water.

The innovative system is a continuation of the theoretical breakthrough by the Technion research team, presented in a June 2017 article in Nature Materials. In that article, the researchers introduced a paradigmatic shift in hydrogen production: Instead of one production cell where the water is broken down into hydrogen and oxygen, the researchers developed a system where hydrogen and oxygen are formed in two completely different cells. This development is important in part because mixing oxygen and hydrogen creates an explosive and dangerous interaction. The researchers presented the proof of feasibility in a laboratory system operated with a conventional power source.

Now, in the current study in Joule, the researchers present the realization of the theory in applied development – a photoelectrochemical prototype system that produces hydrogen and oxygen in two separate cells using only sunlight. As part of the experiment approximately 80 working hours (10 days of about 8 hours) were conducted, demonstrating the efficiency of the system in natural sunlight. The experiment was conducted in the Faculty of Chemical Engineering at the Technion.

The Technology Backstory

The most in-vogue alternative to producing hydrogen from fossil natural gas is electrolysis – decomposition of water for hydrogen and oxygen. 

Against this backdrop, the photoelectrochemical process developed, which breaks down the water directly using the sun’s radiation. 

Although here too, there are various technological challenges. For example, the production of hydrogen using the conventional method of electrolysis – the decomposition of water into hydrogen and oxygen in the same production cell – involves risk because the encounter between hydrogen and oxygen leads to an explosion. Moreover, in large-scale solar fields, it is very difficult to produce hydrogen in this configuration. Hence the importance of the current breakthrough presented in Joule.

The researchers hope that academics and industry will continue and advance the system into a commercial product.

The research was supported by the Nancy and Stephen Grand Technion Energy Program (GTEP), funding from U.S. donor Ed Satell, the Adelis Foundation, Ministry of Energy and the European Commission (two ERC grants), and the National Science Foundation PAT Excellence Center.

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