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Study of new electrocatalysts based on efficient and stable nanoalloys by scanning electrochemical microscopy

Abstract

Proton-exchange membrane fuel cells (PEMFC) are a possible alternative to produce energy. However they cannot yet be used at large scale because of their low efficiency and durability. At present, their main limitation is the performance of oxygen reduction reaction (ORR) occurring at the cathode. This reaction still needs an overpotential of 300 to 600 mV (compared to 20 mV for the anode) and most of the electrocatalysts conventionally used undergo degradation and deactivation1. To reach both, good activity and stability towards ORR, various ideas are explored in the literature based on the modification of shape, size, porosity, chemical composition, etc2. The Palladium:Cobalt alloy (Pd:Co) has been reported in literature3 as an interesting alternative, since exhibits good activity towards ORR. However, Co gets mainly dissolved in acidic solution. The idea of our study to overcome this issue is to selectively oxidize the Co surface on the Pd:Co alloy to preserve its activity while increasing its stability. In the present communication, the Scanning ElectroChemical Microscope (SECM)4,5 is used in pumped-Micropipette Delivery/Substrate Collection (pumped-MD/SC) mode to compare the activity of different catalysts towards ORR. This approach gives as a result an intensity contrasted image (i.e. Figure 1), which allows a direct comparison of multiple catalysts under the same experimental conditions thanks to the microfabrication of the samples. Moreover, the catalysts have been characterized by other techniques such as Electrochemical Impedance Spectroscopy (EIS), which allows us to evaluate the thickness of the oxide layer formed and study its stability. (1) Ge, X. et al. ACS Catal. 2015, 5, 4643-4667 (2) Sánchez Sánchez, C. M. et al. JACS. 2010, 132, 5622-5624 (3) Fernandez, J. et al. JACS. 2005, 127, 357-365 (4) Cannan, S. et al. Phys. Chem. Chem. Phys., 2011, 13, 5403–5412 (5) Sánchez Sánchez, C. M. et al. Electrochem. Soc. Interface, 2014, 23, 43-45
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Dates and versions

hal-03966981 , version 1 (01-02-2023)

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  • HAL Id : hal-03966981 , version 1

Cite

Sophie Juillard, Vincent Vivier, Carlos M Sánchez-Sánchez. Study of new electrocatalysts based on efficient and stable nanoalloys by scanning electrochemical microscopy. 10th International Workshop on SECM and Related Techniques (SECM10), Sep 2019, Paris-Fontainebleau, France. ⟨hal-03966981⟩
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