P-075

Biswaranjan D. Mohapatra

Biswaranjan.mohapatra@ftmc.lt

Joanna Czopor, Izabela Darowska, Mateusz Szczerba, and Grzegorz D. Sulka

Department of Physical Chemistry & Electrochemistry, Faculty of Chemistry, Jagiellonian University, Krakow, Poland.

Evaluation of Oxygen Electrocatalytic properties of Fe doped/modified Ta2O5 and HfO2 Nanostructures

Developing low-cost, earth-abundant oxygen electrocatalysts remains a key challenge for next-generation fuel cells and water splitting devices. While Mn, Fe, and Co-based transition metal oxide/hydroxide nanostructures have been extensively studied, their degradation under operating conditions limits their practical application, motivating further electrode and cell structure engineering and development [1]. Recently, some group 4 or 5 based transition metal oxides; e.g. Ta2O5 doped with Fe/Co have been emerged as promising, cost-effective and stable alternatives [1,2]. The theoretical studies on modified Ta2O5 suggests change in electronic structure, shifting of d-band center of surface Ta atoms and a favorable interaction of the catalyst structures with the reaction intermediates, and thereby by decrement of overpotential (0.30 V) for catalysis compared to pristine Ta2O5 [1,2]. In this context, we synthesized Fe doped/modified Ta2O5 and HfO2 (Fe-Ta2O5 and Fe-HfO2) with varying Fe contents through electrochemical methods (i.e., by anodic oxidation and pulsed potential deposition) [3]. Through controlling the electrochemical parameters (electrolytes composition, applied potential, time, pulse frequency, etc.) we achieved variation in Fe contents in the materials. We demonstrated formation of nanotubes (~30 nm: diameter) and agglomerated nanoparticles sized 50 – 150 nm for Fe-Ta2O5 and of Fe-HfO2 respectively. The morphology, elemental composition, chemical structures, and oxidation states of metals in the materials were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). On the path of optimization of Fe contents in the materials and understanding the electronic interactions between Fe and Ta/Hf on the O2 electrocatalysis, we showed the role of materials crystallinity and loading content (on conductive carbon support) on the O2 catalysis. The electrochemical strategies for designing  Fe-Ta2O5 or Fe-HfO2 nanostructured materials with controlled Fe and impurities contents and understanding the catalytic descriptors (i.e., crystallinity, crystalline phases and loading content) collectively as well as individually may open a new avenue of designing more active oxide based catalysts.

Acknowledgments:

This research is supported by National Science Centre, Poland (project No. 2021/43/P/ST5/02281). 

References:

1. A. Liu et al.,  MRS Commun. 2017, 7, 563.

2. S. Back et al., ChemCatChem 2022, 14, e202101763.

3. B. D. Mohapatra et al., ACS Appl. Nano Mater. 2025, 8, 8865.