Nanostructured Sustainable Materials for Solar Energy Conversion: Fe-Based Absorbers and Catalysts

Efficient conversion and storage of solar energy are crucial steps in the establishment of a renewable and carbon neutral energy supply. Photocatalysis and photoelectrochemistry are considered promising to make use of the large amounts of sunlight that reach the surface of earth. They render the direct conversion of light into chemical energy possible, e.g. solar fuels like hydrogen or ammonia. In recent years, earth-abundant Fe-based materials like spinel ferrites have emerged as auspicious materials for these applications. They have the inherent ability to absorb a large part of the visible light spectrum with band gaps around 2 eV, while some of them being also very good electrocatalysts. My group utilizes modern synthesis techniques to prepare nanostructured Fe-based materials for the generation of solar fuels.<br/>In recent years, we have developed fast microwave-assisted sol-gel syntheses yielding phase-pure spinel ferrite nanoparticles of e.g. MgFe₂O₄, CuFe₂O₄, NiFe₂O_4,MnFe₂O₄ and ZnFe₂O₄ at temperatures as low as 170-200 °C.[1,2] The crystallite size can be tailored in-situ or by post-synthetic heat treatment, however the materials are already (partly) crystalline as-prepared, with specific surface areas of around 200 m²/g and good colloidal stability. Some syntheses even take only several minutes. Photocatalytic and electrocatalytic experiments will be presented, as well as the conversion of some spinel oxides into (oxy)sulfides and pendlandites for electrocatalytic water splitting.[3,4] Moreover, a direct microwave-assisted synthesis for nickel-iron sulphide nanosheets for electrocatalytic CO₂ reduction and photocatalytic HER will also be presented.[5,6]<br/>Finally, the potential of using a heterojunction of iron sulphide and carbon nitride for light-induced reduction of N₂ to ammonia will be introduced.[7]<br/><br/><br/>Literature:<br/>[1] A. Bloesser et al., ACS Appl. Nano Mater. 2020, 3, 11587. [2] C. Simon et al., Chem. Eur. J. 2021, 27, 16990. [3] D. Tetzlaff et al., Faraday Discussions 2019, 215, 216. [4] D. Tetzlaff et al., Energies 2022, 15, 543. [5] C. Simon et al, ACS Appl. Energy Mater. 2021, 4, 8702. [6] J. Zander et al., J. Mater Chem. A 2023, 11, 17066 [7] J. Zander et al., Adv. Energy Mater. 2022, 12, 2202403.