Tailoring high entropy perovskites for green hydrogen production via solid oxide electrolysis

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Introduction and Motivation

Solid oxide electrolysis cells (SOECs) represent a tremendous opportunity for green hydrogen production, as it utilizes high-temperature electrolysis to efficiently split water molecules into hydrogen and oxygen, with the added benefit of utilizing renewable energy sources. This technology holds immense promise for a sustainable future, enabling the large-scale production of clean hydrogen as a versatile and environmentally friendly energy carrier. The present work deals with a promising novel material class for the air electrode of solid oxide cells, which is high entropy perovskites (HEPs). The results show that HEP could be a promising choice for air electrodes for SOEC as well as fuel cell (SOFC) applications.

Theory

  • At least 5 different cations at A or B site increase configurational entropy
  • The high dispersity of several different cations in A-site may cause lattice distortion which might suppress strontium diffusion [1]
  • Cocktail effect may be induced: properties can differ significantly from related elemental compositions

Synthesis

  • La0.2Pr0.2Nd0.2Sm0.2Sr0.2CoO3-  (LPNSSC) was investigated
  • LPNSSC powder was synthesized by the citric acid– ethylenediaminetetraacetate (CA-EDTA) sol-gel method
  • The powder was homogenized and calcined for 4h at 1,000°C

Cell Microstructure and Microstructural Tailoring

Simulating SOEC with different kinds of microstructure attributes, indicate a favorable porosity of more than 30% with grain size down to 0.1µm of most efficient hydrogen production. The images below show a way how to influence microstructural parameters [2].

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Electrochemical Characterization

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  • Left image: Superior cell performance in SOFC mode for LPNSSC and different pore formers compared to state of the art air electrodes (KS = ~30µm potatoes starch, NC = ~0.1 µm nano carbon, AK ~1.5 µm active carbon)
  • Right image: Better long term stability of LPNSSC in SOEC mode compared with La0.6Sr0.4CoO3- . Constant voltage over a wide range means hardly any degradation

Publications / Poster

References

[1] Yang, Y., et al., A novel facile strategy to suppress Sr segregation for high-entropy stabilized La0.8Sr0.2MnO3-δ cathode. Journal of Power Sources, 2021. 482: p. 228959

[2] Wenying, Li, et al., Theoretical modeling of air electrode operating in SOFC mode and SOEC mode: The effects of microstructure and thickness. International Journal of Hydrogen Energy, 2014. 39: p. 13738-1375