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Institute Solar Fuels

Our Projects

NETPEC

Negative emissons via photoelectrochemical methods

Joint project within the BMBF research program on land-based CO₂ removal methods (CDRterra)

BMBF - Funding code: 01LS21038
Durationt: 01.10.2021 bis 31.03.2025

Carbon formation on a liquid GaInSn drop

Electrochemical Studies on CO2 Reduction for the CDRterra approach

The electrochemical reduction of CO2 (CO2RR) offers a sustainable technology for converting CO2 into valuable products when using electricity generated from renewable sources. Application-oriented research is currently focused mainly on the electrolysis of CO2 to hydrogen-rich fuels or chemical feedstock materials. In contrast our project aims to form solid carbon or carbon rich products (e.g. oxalate), which can finally be disposed of in geological repositories (CDRterra). This negative emission technology is developed for a long-term and thereby sustainable CO2 removal from the global CO2 cycle 1. The continuous electrochemical formation of solid carbon from CO2 has so far only been reported on liquid GaInSn-M alloys (M: Ce, V) in water-containing DMF 2,3. Liquid electrodes have the advantage over solid electrodes that solid products do not adhere at the interface and therefore deactivate the catalytic properties of the electrode (coking effect).

At the HZB we first studied GaInSn without additional metal alloying in DMF/H2O/ TBAPF6 electrolyte and demonstrated CO2RR to carbon monoxide and formic acid accompanied by lower quantities of H2. The product distribution (faradaic efficiencies) depends strongly on the water content in the DMF electrolyte. The production rate of CO and HCOOH increases significantly even with small amounts of water. Initial DFT simulations of the CO2RR provide possible explanations of this effect. Furthermore, it was observed that, depending on the applied cathodic potential and water content, metallic Sn/Ga-nano particles are released from the GaInSn surface into the organic electrolyte (expulsion effect) which indicates a accumulation of Sn at the electrochemical interface during CO2 electrolysis 4. In accordance with the literature, our findings confirm the production of carbon flakes from CO2 on cerium modified GaInSn. DFT calculations enable us to conclude that the high affinity of cerium to oxygen is responsible for the change in product selectivity, as it can extract oxygen from CO2.

In addition, lead electrocatalysts are investigated and optimized for the formation of oxalates. By coupling the electrolysis cells with solar cells from the project partner, the solar-driven reduction of CO2 to the corresponding products is ultimately demonstrated and quantified at the HZB.

  1. May, M. M. and Rehfeld, Earth Syst. Dynam.: 2019; 10, 1–7
    doi.org/10.5194/esd-10-1-2019
  2. Dorna Esrafilzadeh, NATURE COMMUNICATIONS; 2019; 10:865 
    doi.org/10.1038/s41467-019-08824-8
  3. Mehmood Irfan, J. Mat. Chem. A, Issue 27; 2023
    doi.org/10.1039/D3TA01379K
  4. Mahroo Baharfar, Chemistry of Materials 2022 34 (23), 10761-10771
    doi.org/10.1038/s41467-019-08824-8