Fraunhofer team creates small ‘green’ hydrogen cell

Technology News | July 9, 2024

By Peter Clarke

Three Fraunhofer institutes have teamed up to develop a modular, solar-powered photoelectrochemical cell (PEC) that produces hydrogen.

In the Neo-PEC joint research project, Fraunhofer specialists have developed a tandem module that is self-sufficient in producing solar-generated green hydrogen.

Electrolysis is the breaking down of water down into hydrogen and oxygen and if the electricity needed for electrolysis comes from renewable sources such as solar panels, the result is termed “green” hydrogen. However, conventional electrolysis equipment is big and high-maintenance.

Direct use of solar energy to split water using what is called a photoelectrochemical cell (PEC) provides an alternative. In the Neo-PEC joint research project, researchers from three Fraunhofer institutes have developed a modular solution that enables hydrogen generation and supply with solar energy in a scalable fashion.

Flat glass

Inside the tandem cell float or plate glass is coated with semiconducting materials on both sides. When the sunlight hits the glass, one side of the module absorbs the short-wavelength light. At the same time, the long-wavelength light passes through the upper layer of glass and is absorbed on the reverse side. The module releases hydrogen on the reverse or cathode side and oxygen on the upper side, which is the anode side.

“We use the vapor phase to form layers just a few nanometers thick on the glass. The structures created in the process have a huge impact on reactor activity, in addition to the actual material properties, which we have also optimized,” said Arno Görne, a manager at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS. The photovoltaic elements linked in the module supply the system with additional voltage – a turbo that accelerates activity while additionally boosting efficiency.

The reactor has an active surface area of half a square meter. The oxygen and hydrogen generated are kept separate. A single module exposed to sunlight under European conditions can generate over 30 kilograms of hydrogen per year over 100 square meters. With this yield, a hydrogen car could travel 15,000 to 20,000 kilometer.

Fraunhofer IKTS researched materials and processing for the photoactive layer. Colleagues at the Fraunhofer Institute for Surface Engineering and Thin Films IST contributed their experience in using physical vapor deposition to coat large areas. The reactor design, low-cost and reliable production, and subsequent evaluation of the modules was in the hands of researchers at the Fraunhofer Center for Silicon Photovoltaics CSP.

A follow up project is planned between the three institutes as well as collaborations with commercial companies for the efficient decentralized generation and supply of hydrogen.