DEPECOR – Direct efficient photoelectrocatalytic CO₂ reduction

CO₂ reduction using an artificial leaf

The emission of greenhouse gases into the atmosphere urgently needs to be reduced, employing carbon-neutral, renewable technologies. The main focus is the concentration of carbon dioxide (CO₂), which accumulates in the atmosphere and needs to be reduced either by extraction from the environment (air, oceans) or directly from industrial processes. The current efforts can be divided according to their expected timeline: While the conversion of CO₂ utilizing new chemical methods could take place relatively quickly, the implementation of a technology based on renewable energy is more complex but has been recently shown to be very promising. The “DEPECOR” project aims to combine highly efficient multi-absorber structures in a systemic approach with structures that have already been established in photovoltaics. Critical interfaces and photovoltages will be adapted for CO₂ reduction, with specific corrosion protection layers and efficient catalysts specially selected according to their material and shape.

The next-generation, innovative device structure

For the non-assisted, direct, sunlight-induced CO₂ reduction, the photoelectrochemical (PEC) cells must generate a photovoltage of approximately 3 V. This is possible with multiple absorber structures based on III-V semiconductors. These PEC cells consist of several stacked semiconductor structures (sub-cells) that absorb the light in different spectral ranges. Thus, effective exploitation of the sunlight spectrum is achieved and the energy losses are significantly reduced compared to single absorber systems. The total voltage is composed of the sum of the voltages of each sub-cell and, therefore, sufficient to drive the chemical reactions directly. In order to achieve these goals, the “DEPECOR” project will be conducted in five parallel parts: The researchers will advance metallic catalysts, which are selective for the photoelectrocatalytic CO₂ reduction and the oxygen evolution reaction. The catalysts will be transferred to
III-V semiconductor test half-cells with thin metaloxide protective layers. The dynamics of the charge carrier transfer and the interfacial recombination processes will be investigated, and the III-V semiconductor half-cells, catalysts, and protective layers will be optimized. At the same time, the highly efficient multi-absorber cells for PEC will be developed. These will be tested and optimized for a non-assisted, efficient light-induced CO₂ reduction.

Strengthened national and international networking

TU Ilmenau (TU-IL) group will develop and test an integrated III-V semiconductor, photoelectrocatalytic
half-cells. To increase the stability of the cells and enhance the performance, metal oxide protective layers will be deposited by atomic layer deposition (ALD) at the TU Munich (TUM), and the heterointerfaces will be examined in cooperation with TU-IL. Highly active catalysts will be developed at the Helmholtz-Zentrum Berlin (HZB) and integrated into the cell structure. The interaction of the photocathode with the electrolyte and the quantitative development of the reaction products will be measured at the TUM, HZB, TU-IL, and the Joint Center of Artificial Photosynthesis (USA). The project partner AZUR SPACE Solar Power GmbH (AZUR) will deliver suitable industrially scalable multi-absorber structures on germanium and III-V substrates. At the same time, the Fraunhofer Institute for Solar Energy Systems (ISE) will develop the layer structures on silicon substrates. The associated partner École Polytechnique Fédérale de Lausanne (EPFL) will investigate the activity of specific Cu catalysts and will support the modeling of the prototype of CO₂ reduction systems for non-assisted fuel production. The project partner AZUR and the associated partners BASF and Evonik will advise the prototype development regarding the technology transfer to develop the planned commercial product.

Interview about DEPECOR

Depecor project sheet download