- Researchers at Germanyโs Jรผlich Institute for Energy and Climate Research (IEK-5) have created a photovoltaicโelectrochemical (PV-EC) water-splitting device powered by solar energy.
The integrated PV-EC device with an active area of 0.5 cm2 was developed with solar panels based on tripleโjunction thinโfilm silicon solar cells with an efficiency rating of 10.8% and an electro-deposited bifunctional nickel iron molybdenum waterโsplitting catalyst.
โThe introduction of a tripleโjunction Si solar cell offers the possibility of manufacturing a selfโcontained base unit without the need for additional series interconnection, which is normally required when using singleโ or doubleโjunction solar cells,โ the research team said, adding that a similar approach may also result in more efficient and cheaper devices, as dead areas created by interconnections are avoided. Their efficiency increases by reducing the dead area and increasing their active area.
With an aperture area of 64 cm2 and an active area of 56 cm2, the wireless solar panel is able to provide an openโcircuit voltage of approximately 2.16 V and a voltage at the maximum power point of about 1.72 V, which the scientists claim is enough to enable biasโfree water splitting.
As for the water-splitting catalyst, the scientist developed a bifunctional NiFeMo device prepared by electrodeposition.
โThe bifunctional catalysts enable the PVโEC system to get rid of the need for two different catalyst materials for the anode and cathode side, which offers the potential for lower costs of catalyst production and system configuration,โ the academics explained. The gas separation membrane, the solar panels, and the catalysts were mounted in a 3D-printed frame.
Compared to conventional waterโsplitting systems, the new device is said to have a better light absorbing path, thanks to the superstrate configuration of the solar cells, without inevitable losses due to the interruption of catalysts and bubbles. The catalyst is not transparent and it can absorb some of the lightโs wavelengths
The PV-EC device had an initial solarโtoโhydrogen (STH) efficiency of approximately 7.7% and after 100 hours of operation this efficiency dropped by 17% to 6.40%. โThe upscaled prototype device with an aperture area of 64 cm2 was found to be stable for 30 minutes,โ researcher Minoh Lee told pv magazine. โAlthough our upscaled device has shown relatively rapid decrease of the STH efficiency, it is still worth noting that the gas separation is first demonstrated in such a bias-free and wireless device at large scale.โ
Lee said the main reason for the failure is the use of improper supporting components, such as unsuitable adhesives between the device body and back cover glass, as well as the unfavorable design of the gas separation, rather than the degradation of PV and the electrocatalyst.
โWe expect that the upscaling device can be more stable if suitable design of gas separation is applied and proper adhesive is used in the upscaling device,โ Lee added. โIf that were to happen, it would be possible to commercialize this technology soon.โ
The researchers discuss the device in A BiasโFree, StandโAlone, and Scalable PhotovoltaicโElectrochemical Device for Solar Hydrogen Production, recently published in Advanced Sustainable Systems
Author: Emiliano Bellini
This article was originally published in pv magazine and is republished with permission.