Analysis

Artificial photosynthesis could improve solar fuels

7th March 2017
Enaie Azambuja

EU-funded materials scientists, chemical engineers and chemists developed a prototype device that converts solar energy into hydrogen with close to 10% efficiency at room temperature. Solar energy is available everywhere and is often abundant, even in densely populated areas as well as Northern Europe. There is enough solar energy to allow a shift from fossil fuels despite the current modest conversion efficiencies of solar energy to electricity or solar fuels.

For the widespread adoption of solar energy, it is critical that efficient processes are developed. The project ARTIPHYCTION (Fully artificial photo-electrochemical device for low temperature hydrogen production) took inspiration from the natural photosynthesis process in plants to convert solar energy into hydrogen.

In photosynthesis, the Photosystem II (PSII) enzyme enables plant leaves and algae to split water into electrons, oxygen and hydrogen ions at room temperature. These can later be combined into non-negligible amounts of hydrogen with a specific enzyme called hydrogenase.

Harnessing the Sun's light in such a way is one of the most promising processes for converting its energy into hydrogen. ARTIPHYCTION partners built on the pioneering work performed in a previous EU-funded project, SOLHYDROMICS where a device was developed converting solar energy to hydrogen with an overall efficiency of 1%.

Project partners overcame SOLHYDROMICS device limitations and achieved an efficiency of over 10% for solar hydrogen generation in a new artificial photosynthesis device. This features specially designed electrochemically-tailored catalysts at the anode where water is split.

The generated electrons are conveyed through a porous electron-conducting glass layer to an external wire connection and the oxygen is removed via hydrophobic pores of the anode layers. Waves generated by pressure fluctuations applied on a water film separating the two electrodes facilitate oxygen removal.

The water sandwiched between the electrodes also serves as a pathway for the protons, which are transferred to the cathode electrode with minimum resistance. A synthetic hydrogenase-mimetic catalyst on the porous cathode ensures the final reduction of protons.

The ARTIPHYCTION device relies on efficient and stable electrocatalysts rather than the natural enzyme hydrogenase. To enhance photo-electrochemical water splitting, a tandem system of photosensitisers capturing certain light wavelengths was tethered at both electrodes.

By combining the scientific rigour of universities and research centres with the knowledge of the commercial marketplace of small and medium-sized enterprises and large companies, ARTIPHYCTION succeeded in solving several technical issues. The new synthetic photosynthesis device is expected to be commercialised in the next ten years.

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