Structuring High-Entropy Oxides at the Nanoscale: Ordered Mesoporous (CrMnFeCoNi)Ox Thin Films for High-Performance Oxygen Evolution Reaction Catalysis
4 affiliations
- 1Department of Materials- and Geosciences, Technical University of Darmstadt, Peter-Grünberg-Strasse 4, Darmstadt, Germany, 64287
- 2Institute for Applied Geosciences, Atmospheric Aerosol
- 3Technical University of Darmstadt Schnittspahnstrasse
- 4Department of Materials and Earth Sciences, Technical University of Darmstadt, Peter-Grünberg-Strasse 2, Darmstadt, Germany, 64287
Abstract
The synthesis of high-entropy oxides (HEOs) with nanoscale architectures is challenging, since both the peculiar crystalline structure with statistical element occupancy and the desired nanomorphology must be controlled. Here, ordered mesoporous (spinel) (CrMnFeCoNi)Ox HEO thin films were prepared via soft-templating and dip-coating under tailored synthesis conditions, and the influence of calcination temperature on their structural evolution and alkaline oxygen evolution reaction (OER) performance was investigated. Electron microscopy revealed a temperature-dependent development of an ordered mesoporous architecture with 15–20 nm pores using polyisobutylene-block-poly(ethylene oxide) (PIB-b-PEO) as structure-directing agent. Energy-dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy demonstrated a near-equiatomic, spatially homogeneous distribution of all transition metals at the surface and in the bulk. Transmission electron microscopy and X-ray diffraction revealed a temperature-induced transition from an amorphous to nanocrystalline cubic spinel structure at 600 °C. X-ray photoelectron spectroscopy indicated a transformation from a high-valence, defective/hydroxylated surface composition rich in Cr6+, Mn3+, Co2+, and Ni2+ species at 300–400 °C to more low-valence surface states with increased lattice-oxygen contribution at 500–600 °C. The mesoporous HEO thin film annealed at 400 °C for 5 min exhibited one of the best OER performances ever reported (η10 = 273 mV at 10 mA cm−2 and Rct = 3.9 Ω at 1.5 V vs. RHE) in alkaline electrolyte. Overall, the structural evolution and OER performance of HEO thin films follow a temperature-dependent activity trend based on the balance and interplay of surface area, crystallinity, oxygen defects, and catalytically active species at the surface, highlighting the necessity of precise control of the synthesis conditions and formulation of structure-property relationships for improving the OER performance of compositionally complex catalysts.
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BibTeX
@misc{wu2026structuring,
title = {{Structuring High-Entropy Oxides at the Nanoscale: Ordered Mesoporous (CrMnFeCoNi)Ox Thin Films for High-Performance Oxygen Evolution Reaction Catalysis}},
author = {Qingyang Wu and Ann-Kristin Stief and Hikmet Sezen and Stefan Lauterbach and Barbara Gonzalez-Navarrete and Marc Widenmeyer and Jan P. Hofmann and Marcus Einert},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010129/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010129/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Structuring High-Entropy Oxides at the Nanoscale: Ordered Mesoporous (CrMnFeCoNi)Ox Thin Films for High-Performance Oxygen Evolution Reaction Catalysis
AU - Qingyang Wu
AU - Ann-Kristin Stief
AU - Hikmet Sezen
AU - Stefan Lauterbach
AU - Barbara Gonzalez-Navarrete
AU - Marc Widenmeyer
AU - Jan P. Hofmann
AU - Marcus Einert
PY - 2026
DA - 2026/10/08
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010129/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010129/v1
AB - The synthesis of high-entropy oxides (HEOs) with nanoscale architectures is challenging, since both the peculiar crystalline structure with statistical element occupancy and the desired nanomorphology must be controlled. Here, ordered mesoporous (spinel) (CrMnFeCoNi)Ox HEO thin films were prepared via soft-templating and dip-coating under tailored synthesis conditions, and the influence of calcination temperature on their structural evolution and alkaline oxygen evolution reaction (OER) performance was investigated. Electron microscopy revealed a temperature-dependent development of an ordered mesoporous architecture with 15–20 nm pores using polyisobutylene-block-poly(ethylene oxide) (PIB-b-PEO) as structure-directing agent. Energy-dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy demonstrated a near-equiatomic, spatially homogeneous distribution of all transition metals at the surface and in the bulk. Transmission electron microscopy and X-ray diffraction revealed a temperature-induced transition from an amorphous to nanocrystalline cubic spinel structure at 600 °C. X-ray photoelectron spectroscopy indicated a transformation from a high-valence, defective/hydroxylated surface composition rich in Cr6+, Mn3+, Co2+, and Ni2+ species at 300–400 °C to more low-valence surface states with increased lattice-oxygen contribution at 500–600 °C. The mesoporous HEO thin film annealed at 400 °C for 5 min exhibited one of the best OER performances ever reported (η10 = 273 mV at 10 mA cm−2 and Rct = 3.9 Ω at 1.5 V vs. RHE) in alkaline electrolyte. Overall, the structural evolution and OER performance of HEO thin films follow a temperature-dependent activity trend based on the balance and interplay of surface area, crystallinity, oxygen defects, and catalytically active species at the surface, highlighting the necessity of precise control of the synthesis conditions and formulation of structure-property relationships for improving the OER performance of compositionally complex catalysts.
ER -