Bridging the Understanding between Oxygen Electrocatalysis Activity and Electrode Stability in Acidic Medium: An Approach Towards Designing Low-cost PEM Fuel cells and Water Electrolyzers (BOEESA_PEM-2021)

Korelacja między aktywnością katalizatora tlenowego a stabilizacją elektrod w środowisku kwasowym: Podejście do projektowania niskokosztowych ogniw paliwowych PEM i elektrolizerów wodnych

This project is focused to design Iron (Fe) or Nickel (Ni) containing Tantalum oxide (TaOx) and Hafnium oxide (HfOx) nanomaterials for efficient and stable oxygen electrocatalysis application. The desired nanostructured materials will be synthesized by electrochemical methods (i.e., by electrochemical anodization and electrodeposition). The morphology and elemental composition of the materials will be investigated by various sophisticated analytical and spectroscopic techniques; X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The oxygen electrocatalysis properties of the materials will be investigated in acidic electrolytes by employing a computer controlled potentiostat/galvanostat. The relationship between the catalytic activity and electrode stability will be established. We hope such a detailed study of designing highly active Fe/Ni-TaO_x and Fe/Ni-HfO_x materials and understanding their activity-stability issues will enrich our knowledge of acidic oxygen electrocatalysis. 

This research is part of the project No. 2021/43/P/ST5/02281 co-funded by the National Science Centre and the European Union Framework Programme for Research and Innovation Horizon 2020 under the Marie Skłodowska-Curie grant agreement no. 945339.

Principal Investigator: Biswaranjan Das Mohapatra

Project location

Faculty of Chemistry, Department of Physical Chemistry and Electrochemistry, Jagiellonian University
Gronostajowa 2, Krakow 30-387, Poland
www.chemia.uj.edu.pl (faculty website)
www.elektro.chemia.uj.edu.pl (group website)

The scholarship holders working in the project will be students:

1. Izabela Darowska
2. Mateusz Szczerba

Project news

The nanoporous/nanotube structures of anodic TaO_x, Fe-TaO_x and HfO_x has been optimized in fluoride ion containing H₂SO₄ /ethylene glycol electrolytes. The pore diameter and thickness of the doped and undoped oxide (TaO_x and HfO_x) layers was varied by controlling the anodization parameters (e.g., applied potential, anodization time, composition of electrolyte and temperature of electrolyte). The effect of annealing conditions (400-600 °C, air atmosphere) of the anodic oxide materials on their crystallinity and O₂ electrocatalysis (O₂ reduction and evolution reaction) activity was evaluated. The percentage of H₂O₂ production and electron transfer number (n) during O₂ reduction (ORR) were calculated for all the catalysts.

Apart from the anodic structures, TaO_x and HfO_x electrodeposited (potentiostatically) on graphite foil were investigated for oxygen electrocatalysis application. The depositions were carried out at -1.5 and -1.7 V vs. SCE for 120 seconds in 50 mM TaCl₅ or HfCl₄ + 1 M KCl + 0.5 M KNO₃ bath. All TaO_x and HfO_x deposited samples were annealed in air atmosphere for 5 h in 300 °C to investigate the effect of annealing conditions on the oxide phases of the materials. The materials demonstrated cathodic current for O₂ reduction at about 0.1 V vs. SCE. The cyclic voltammetry (CV) graph for TaO_x/graphite showed O₂ reduction current density of -1.1 mA cm^-2 at -0.3 V and this value for HfO_x/graphite catalyst was -1.35 mA cm^-2. These results qualitatively demonstrate the electrocatalytic ORR activity of TaO_x and HfO_x deposited graphite materials in acidic electrolyte. Rotating ring disk electrode (RRDE) studies are under progress to quantitatively investigate the ORR activities of these materials.

Publications from the Project and Some Highlights for The Project Work

1. B.D. Mohapatra , K. Pawlik, I. Darowska, Ł. Gondek, M. Pisarek, G.D. Sulka,  Understanding the morphological evolution of anodic tantalum oxide nanostructures in acidic medium, Mater. Adv. 5 (2024) 6560-6571. https://doi.org/10.1039/D4MA00458B

• The electrochemical anodization parameters influencing formation of nanoporous, nanotube and nanorod layers of anodic Ta₂O₅ were highlighted.
• Conditions for transition of nanoporous anodic Ta₂O₅ layers to nanotube layers were analysed in this study.
• The electrochemical anodization parameters controlling the pore diameter and thickness of anodic Ta₂O₅ layers were analysed thoroughly in this study.
• The rate limiting steps of Ta₂O₅ growth under different potentiostatic conditions were elucidated in this work.

2. B.D. Mohapatra , G.D. Sulka,  Review of anodic tantalum oxide nanostructures: From morphological design to emerging applications, ACS Appl. Nano Mater. 7 (2024) 13821-14843. https://doi.org/10.1021/acsanm.4c02000

• The latest progress in understanding the growth mechanism of nanoporous/nanotubular anodic tantalum oxide (ATO) structures is outlined in this work. 
• The impact of annealing temperature (ranging from 400−1000 °C) and atmosphere on the crystalline structure, morphology, impurity content, and physical properties of the ATOs is briefly covered and described. 
• The common modification methods, such as decorating with other transition metal/metal oxide, heteroatom doping, or generating defects in the ATO structures, are discussed. 
• This review also covers the most promising applications of these materials in the fields of capacitors, supercapacitors, memristive devices, corrosion protection, photocatalysis, photoelectrochemical (PEC) water splitting, and biomaterials.

3. M. Szczerba, B.D. Mohapatra, M. Pisarek, G.D. Sulka, Growth characteristics and physicochemical properties of nanoporous hafnium oxide layers prepared by anodic oxidation of Hf, J. Mater. Res. Technol. 33 (2024) 4137-4148.

• The feasibility of tuning unordered nanopores to ordered nanopores of anodic HfO₂ (AHO) layers is explored by varying the electrochemical anodization conditions in acidic electrolytes.
• The exclusive effects of anodizing time and NH₄F concentration on the mean pore diameter, porosity, and the thickness of AHO layer were evaluated in this study.
• The maximum mean porosity of 24.5 %, pore diameter of 39.8 nm, and the layer thickness of 24.6 µm were observed for AHO layers produced for 60 min at 60 V.
• The rate limiting steps of AHO growth under different potentiostatic conditions were elucidated in this work.

Contact details

Principal Investigator’s contact details:
Biswaranjan Das Mohapatra, PhD
Assistant professor
Jagiellonian University, 
Department of Physical Chemistry and Electrochemistry
Gronostajowa 2, Krakow 30–387, Poland
E-mail: biswaranjan.mohapatra@uj.edu.pl 
Phone: +48 12 686 25 73 

Project Supervisor/mentor’s contact details

Prof. dr. hab. Grzegorz Sulka
Jagiellonian University
Department of Physical Chemistry and Electrochemistry
Gronostajowa 2, 30–387 Krakow, Poland
E-mail: sulka@chemia.uj.edu.pl
Phone: +48 12 686 25 18