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Alkaline fuel cells (AFC) and anion exchange membrane fuel cells (AEMFC) have exhibited attractive advantages versus their acid counterparts, including the strategical possibility of using PGM-free catalysts in the electrode composition.[1,2] PGM-free catalysts remain a challenge regarding the hydrogen oxidation reaction (HOR) catalysis, due to the reduced initial and long-term performance so far.[3,4] PGM-based materials have the highest HOR performances,[5] but Pt- and Pd-based catalysts undergo detrimental metallic nanoparticles detachment from the carbon support and agglomeration (in minor extent) upon extended potential cycling in the alkaline environments.[6,7] In this work, we explore the effect of long-term durability on the nanoparticles wrapped by a carbon layer, labeled here as capped catalysts; two different types of carbon-capped catalysts are evaluated, such as monometallic (PdG2/C) and bimetallic (PdNiG2/C) against their commercial ones (Pd/C and PdNi/C from Premetek). All the catalysts were evaluated in RDE set-up, in couple with IL-TEM, XPS and ICP-MS techniques for before and after accelerated stress test (0.1 – 1.23 V vs. RHE – 3s each potential), up to 6000 cycles. The durability enhancement is achieved when: i) there is a carbon-cap and ii) there is a second metal (i.e. Ni) on the surface of Pd. Thus, in the case of carbon-capped bimetallic (PdNiG2/C), there is a double protection of the Pd nanoparticles (from the carbon-cap and the presence of nickel). In the same time, the HOR activity is high. In the end, the best compromise of durability follows the trend: PdNiG2/C > PdNi/C > PdG2/C > Pd/C. These positive features of the carbon-capped bimetallic material open the way to the design of robust catalysts for highly-durable anodes for alkaline fuel cell systems. [1] D. R. Dekel, J. Power Sources 2018, 375, 158–169. [2] E. Wagner, H. ‐J. Kohnke, Fuel Cells 2020, 1–12. [3] A. G. Oshchepkov, G. Braesch, A. Bonnefont, E. R. Savinova, M. Chatenet, ACS Catal. 2020, 10, 7043–7068. [4] W. E. Mustain, M. Chatenet, M. Page, Y. S. Kim, Energy Environ. Sci. 2020, 13, 2805–2838. [5] W. Sheng, M. Myint, J. G. Chen, Y. Yan, Energy Environ. Sci. 2013, 6, 1509–1512. [6] C. Lafforgue, F. Maillard, V. Martin, L. Dubau, M. Chatenet, ACS Catal. 2019, 9, 5613–5622. [7] A. Zadick, L. Dubau, N. Sergent, G. Berthomé, M. Chatenet, ACS Catal. 2015, 5, 4819–4824. |
