Chemical Solution Synthesis of Copper-Iron Delafossite Photocathode Materials for Photoelectrochemical CO2 Conversion
Nele Debusschere a c, Bjorn Joos a b c, Ken Elen a b c, Pegie Cool d, Marlies Van Bael a b c, An Hardy a b c
a UHasselt, Institute for Materials Research (IMO-IMOMEC), DESINe, Agoralaan, building D, 3590 Diepenbeek, Belgium.
b IMEC vzw, IMOMEC Associated Laboratory, Wetenschapspark 1, B-3590 Diepenbeek, Belgium.
c Energyville, Thor Park, 8320 Genk, Belgium.
d University of Antwerp, Laboratory of Adsorption and Catalysis (LADCA), Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk, Belgium.
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#ChemNano23 - Chemistry of Nanomaterials
València, Spain, 2023 March 6th - 10th
Organizers: Loredana Protesescu and Maksym Yarema
Poster, Nele Debusschere, 352
Publication date: 22nd December 2022

While continuously alarming reports regarding climate disasters appear in the media, the need for reduction of CO2 emissions becomes more urgent. An interesting solution is converting the harmful CO2 into a value-added chemical, such as methanol. The CO2 reduction can be realized in a photoelectrochemical cell, using a combination of solar energy and renewable electricity to provide the necessary energy. To design this system, efficient and selective semiconducting photoelectrodes which are also stable, low cost and non-toxic are needed.1,2 To achieve this, key characteristics of the photoelectrodes include for example their conduction band edge and bandgap. The aim in this project is to fabricate the CuFeO2 delafossite as a photocathode material. The delafossite is attractive as a natural p-type semiconductor that, compared to cuprous oxide, has shown a higher electrochemical stability, improved hole mobility and less susceptibility to photodegradation. However, it is challenging to synthesize this material, as it is a metastable, high temperature phase, existing only between 1015°C and 1090°C according to the thermodynamic copper-iron oxide phase diagram.3 Therefore, in the research at hand, a hydrothermal synthesis route for the delafossite CuFeO2 was studied. In general, hydrothermal methods are good candidates for the synthesis of metastable phases at low temperature. However, in literature, the hydrothermal synthesis for CuFeO2 is often reported without much attention to the detailed effects of the many different synthesis parameters nor to controlling reproducibility, which is known to require great care. Therefore, a systematic investigation of the synthesis process was conducted by a variation of important synthesis parameters such as the Cu/Fe ratio, reaction time and temperature. It was concluded that the formation of the delafossite CuFeO2 was obtained via a solution-based hydrothermal process after 12 hours at 120°C at various Fe/Cu ratios except for the Fe/Cu 1/1 ratio. The phase formation was verified by x-ray diffraction and Raman spectroscopy. Furthermore, the bandgap was studied with UV-vis spectroscopy and the sample surface and morphology were studied with TEM and Raman mapping. In conclusion, the CuFeO2 delafossite appears to have the potential to be a promising photocathode material for CO2 reduction.

First, I would like to thank my promotor An Hardy for always giving the necessary input in my research and for giving me the ability to attend this conference. Then I would like to thank my co-promotor Marlies Van Bael and my promotor from the University of Antwerp Pegie Cool for the feedback on my work. Then I would also like to thank Bjorn Joos and Ken Elen for the more hands-on advice and suggestions for my experiments and research output. Finally, I would like to thank Vlaio-Catalysti for funding the SYN-CAT project that I am currently working on. I would also like to thank my partners of the SYN-CAT project for giving valuable feedback during our project meetings. Furthermore, I want to thank Gianfabio Mangione for measuring the Raman spectra of my samples and Naomi Billiet for XRD measurements. Finally, I would like to thank my colleagues in the DESINe group for giving many useful ideas and feedback.

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