Synthesis of Rhodium Electrocatalyst Nanoparticles for Photoelectrochemical Water-Splitting in Microgravity

Camilla Tossi^a^,^b, Sousan Salehi^c, Katharina Brinkert^a^,^d

^aCenter of Applied Space Technology and Microgravity (ZARM), University of Bremen, 28359 Bremen, Germany

^bCenter for Nanotechnology Innovation, Istituto Italiano di Tecnologia, Pisa, Italy

^cUniversity of Bremen, Germany

^dDepartment of Chemistry, University of Warwick, CV47AL, Coventry, United Kingdom

Proceedings of MATSUS Fall 2026 Conference (MATSUSFall26)

E2 Solar fuels and chemicals: from devices to discoveries in unconventional environments

Palma, Spain, 2026 October 26th - 30th

Organizers: Franky Esteban Bedoya Lora, Katharina Brinkert and Anna Hankin

Invited Speaker, Camilla Tossi, presentation 031
Publication date: 22nd July 2026

Long-term missions to Moon and Mars will require in-situ resource utilization (ISRU) technologies to synthesise materials in harsh environments and reduced gravitation. This opens a path for research on the sustainable fabrication and synthesis of materials potentially utilised in energy conversion technologies in these environments[1,2].

Photoelectrochemical (PEC) energy conversion is currently investigated for space applications, due to its potential in converting water and carbon dioxide using sunlight into oxygen, hydrogen, and useful carbon compounds[1,2]. Further, the monolithic design of PEC devices, which includes integrated semiconductor-electrocatalyst systems, offers significant advantages for long-term space missions, such as a compact and lightweight payload[3]. Particularly important is hereby the choice of electrocatalyst material (metal(s) or metal alloys) for the respective anticipated redox reaction to minimize activation polarization overpotentials of the device[4].

Since microgravity is known to affect the synthesis of nanomaterials by inducing increased crystallinity and increased porosity - which are attractive qualities in a catalyst material - the present study investigates the effect of this environment on the synthesis of Rhodium nanoelectrocatalysts via photoelectrodeposition, conducted in the Bremen Drop Tower (Germany)[5,6].

We present the different morphologies obtained in gravity- versus microgravity-bound synthesis processes, and compare their performance as catalysts for the hydrogen evolution reaction in both environments.

References:

[1] Hoffman, J. A. et al. Mars Oxygen ISRU Experiment (MOXIE) - Preparing for human Mars exploration. Sci. Adv. 8, eabp8636 (2022)

[2] Starr, S. O. and Muscatello, A. C. Mars in situ resource utilization: a review. Planet. Space Sci. 182, 104824 (2020)

[3] Ross, B., Haussener, S. Brinkert, K. Assessment of the technological viability of photoelectrochemical devices for oxygen and fuel production on Moon and Mars. Nat. Commun. 14, 3141 (2023)

[4] Cheng, W.-H. et al. Monolithic Photoelectrochemical Device for Direct Water Splitting with 19% Efficiency. ACS Energy Lett. 3, 1795–1800 (2018)

[5] Fukunaka, Y., Okano, K., Tomii, Y., Asaki, Z. Kuribayashi, K. Electrodeposition of Copper under Microgravity Conditions. J. Electrochem. Soc. 145, 1876 (1998)

[6] Akay, Ö., Poon, J., Robertson, C., Firdaus Abdi, F., Roldan Cuenya, B., Giersig, M., and Brinkert, K., Releasing the Bubbles: Nanotopographical Electrocatalyst Design for Efficient Photoelectrochemical Hydrogen Production in Microgravity Environment. Adv. Sci. 9, 2105380 (2022)

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