2062
(Invited) Correlation between the Porosimetric Features, Morphology, “Ex-Situ” and “in-Situ” electrochemical Performance of Hierarchical “Core-Shell” Carbon Nitride Pt-Alloy ORR Electrocatalysts

Tuesday, 31 May 2022: 09:10
West Meeting Room 122 (Vancouver Convention Center)
E. Negro (Centro Studi “Giorgio Levi Cases”, University of Padova, Dept. of Industrial Engineering, University of Padova), K. Vezzu (INSTM, Dept. of Industrial Engineering, University of Padova), F. Lorandi, G. Pagot (Dept. of Industrial Engineering, University of Padova, Centro Studi “Giorgio Levi Cases”, University of Padova), G. Zuliani, Y. Bang (Dept. of Industrial Engineering, University of Padova), P. J. Kulesza, I. A. Rutkowska (University of Warsaw, Department of Chemistry), and V. Di Noto (Dept. of Industrial Engineering, University of Padova, INSTM)
The widespread commercialization of proton-exchange membrane fuel cells (PEMFCs) is still bottlenecked by the high loading of platinum-group elements (PGMs), typically platinum, in the cathodic electrocatalytic layer. One strategy to overcome the sluggish kinetics of the oxygen reduction reaction (ORR) taking place at the PEMFC cathode is to increase the mass activity of Pt by implementing Pt-alloy electrocatalysts (ECs) [1]. This strategy allows to decrease the overall Pt loading in the membrane electrode assembly (MEA), the crucial functional component at the heart of the PEMFC.

This contribution discusses “core-shell” hierarchical ECs (H-ECs) consisting of: (i) a hierarchical “core” comprising a blend of nanostructured carbons, that are covered by (ii) a carbon nitride (CN) “shell” wherein Pt-alloy active sites are stabilized by C- and N- ligands in “coordination nests” [2]. The active sites are based on Pt together with Ni and Cu as “co-catalysts” to enhance the ORR kinetics [3]. The bulk of the support of the H-ECs is minimized to promote mass transport phenomena.

The morphology of the H-ECs is probed by ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM), and is discussed in relation to the synthetic parameters and chemical composition. In a second step, nitrogen physisorption techniques are used to evaluate the porosimetric features of the H-ECs, including the specific surface area and the size distribution of the pores. The porosimetric and morphological features are correlated with the electrochemical performance of the H-ECs as measured: (i) “ex-situ”, via cyclic voltammetry with the thin-film rotating ring-disk electrode method (CV-TF-RRDE); and (ii) in single PEMFC under operating conditions as a function of the partial pressure of oxygen in the cathodic feed. A new framework is finally proposed to rationalize and quantify the porosity-morphology-performance correlation for the H-ECs.

References

[1] Y. Sun, S. Polani, F. Luo, S. Ott, P. Strasser, F. Dionigi. Nature Commun. 12, 5984 (2021).

[2] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn. Electrochem. Soc. Interface, 24, Summer 2015, 59-64 (2015).

[3] V. Di Noto, E. Negro, A. Bach Delpeuch, F. Bertasi, G. Pagot, K. Vezzù, Patent application PCT/EP2017/084801 (2017).

Acknowledgements

The described research has received funding from: (a) the European Union's Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project "Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells" funded by EIT Raw Materials; and (c) the project "Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells e HELPER" funded by the University of Padova.

See more of: L05 - Mechanistic Aspects of Oxygen Reduction
See more of: L05: Mechanistic Understanding of Electrocatalytic Electrodics of Oxygen, Hydrogen, and Carbon Dioxide Electrochemistry
See more of: Physical and Analytical Electrochemistry, Electrocatalysis, and Photoelectrochemistry
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