Towards a Solar Cell for the Production of Methanol

500.000 euro NWO 'Solar to Products' grant

solar cell
Image: HIMS

Researchers of the University of Amsterdam’s Van ‘t Hoff Institute for Molecular Sciences (HIMS) are working on a new type of ‘chemical’ solar cell that utilizes sunlight for the synthesis of methanol from carbon dioxide and water. The Netherlands Organisation for Scientific Research NWO has funded the research under supervision of prof. Joost Reek with a grant of half a million euros. The research is performed in cooperation with the German chemicals company Merck and the Dutch research institutes ECN and FOM-AMOLF.

Efficient harvesting of solar light can provide the world with enough energy to allow the complete phasing out of fossil fuels. For many applications, cost-effective storage of solar energy is crucial for the future energy infrastructure.

The direct conversion of solar energy into fuel (solar fuel) can provide for this need for storage and photoelectrochemical cells (PECs) are an appealing strategy to realise this. In these cells the formation of the chemicals occurs at the physically separated anode and cathode, simplifying the isolation of the products (oxygen and fuel).

Prevent charge recombination

The Amsterdam chemists are developing a so-called molecular dye-sensitized photoelectrochemical cell (DSPEC) capable of reducing CO2 to methanol (or formic acid or even alkanes). DSPECs have great potential to realize very high efficiencies at low costs because their properties can be tailored by synthetic modification. However, the efficiency for DSPECs for solar energy conversion is still very low (< 0.1%) since the recombination of photochemically generated charges competes with the catalytic reactions that leads to the products.

solar cell
Schematic representation of a Solar Fuel photoelectrochemical cell for methanol production. Image: HIMS.

In the current project funded by NWO the HIMS researchers investigate the use of so-called redox mediators to prevent charge recombination in DSPECs. By doing so they expect to realise at least an order of magnitude increase (from state-of-the-art <0.1% to 1-10%) in the energy conversion efficiency of DSPECs, making a huge step forward towards the deployment of large scale solar energy storage systems.

Consortium

The research project Redox Mediators in Dye-sensitized Photoelectrochemical Cells for CO2-reduction will last four years and will employ two PhD students. It will be performed in a consortium with UvA/HIMS (prof.dr. Joost Reek, dr. Remko Detz and prof.dr. Fred Brouwer), research institutes ECN (prof.dr. Wim Sinke) and FOM-AMOLF (dr. Erik Garnett), and the German chemicals company Merck (dr. Matthias Koch). Merck will also make a contribution to the project funding.

The new research project adds to the SOLARDAM research portfolio and builds on earlier PhD research by Hung-Cheng Chen, who graduated earlier this year on his thesis ‘Solar fuels via artificial photosynthesis‘ under the supervision of prof. Joost Reek (Homogeneous, Supramolecular and Bio-Inspired Catalysis) and prof. Fred Brouwer (Molecular Photonics). A patent has already been applied for. This led ir. Willem Fokkema and Jennifer Nyavor (student in Science, Business and Innovation) at the Innovation Exchange Amsterdam (IXA, the UvA’s technology transfer office) to scout for companies to participate in further development, leading to the cooperation with Merck.

solar cell
Sustainable Earth, image by Samc3352 – Dreamstime

Circular Economy

The focus of the NWO Solar-to-Products programme is on the direct or indirect storage of solar energy by converting carbon dioxide and water in chemical bonds. From the global perspective the ultimate target of this programme is a transformation from an economy based predominantly on energy and materials derived from fossil resources, to an economy driven by mainly solar energy in which material cycles are closed (a circular economy).