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Carbon supported Pd-Cu nanoalloys: support and valence band structure influence on reduction and oxidation reactions.

ABSTRACT: The present study has tracked the changes in the electronic and structural properties of Pd-Cu nanoalloys that were influenced by the composition and chosen support. Carbon supported Pd-Cu nanoalloys (Pd _x Cu_1-x /C for x = 1, 0.7, 0.5, 0.3 and 0) were subjected to sequential thermal treatments (up to 450 °C) to induce reduction and oxidation reactions. Valence band photoemission data and in situ XAS results showed that stronger oxygen-metal bonds are formed in Cu-richer samples. A regeneration process assisted by the support was observed during the oxidation reaction, and its reduction efficiency was found to be dependent on the distribution of occupied electronic states near the Fermi level.

SUBMITTER: Castegnaro MV

PROVIDER: S-EPMC9417155 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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Carbon supported Pd-Cu nanoalloys: support and valence band structure influence on reduction and oxidation reactions.

Castegnaro Marcus V MV Gorgeski Andreia A Alves Maria C M MCM Morais Jonder J

Nanoscale advances 20210826 21

The present study has tracked the changes in the electronic and structural properties of Pd-Cu nanoalloys that were influenced by the composition and chosen support. Carbon supported Pd-Cu nanoalloys (Pd x Cu1-x /C for x = 1, 0.7, 0.5, 0.3 and 0) were subjected to sequential thermal treatments (up to 450 °C) to induce reduction and oxidation reactions. Valence band photoemission data and in situ XAS results showed that stronger oxygen-metal bonds ...[more]

PMID: 36133948

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Project description:Ag-based electrocatalysts are promising candidates to catalyze the sluggish oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFC) and oxygen evolution reaction (OER) in unitized regenerative fuel cells. However, to be competitive with existing technologies, the AEMFC with Ag electrocatalyst must demonstrate superior performance and long-term durability. The latter implies that the catalyst must be stable, withstanding harsh oxidizing conditions. Moreover, since Ag is typically supported by carbon, the strict stability requirements extend to the whole Ag/C catalyst. In this work, Ag supported on Vulcan carbon (Ag/VC) and mesoporous carbon (Ag/MC) materials is synthesized, and their electrochemical stability is studied using a family of complementary techniques. We first employ an online scanning flow cell combined with inductively coupled plasma mass spectrometry (SFC-ICP-MS) to estimate the kinetic dissolution stability window of Ag. Strong correlations between voltammetric features and the dissolution processes are discovered. Very high silver dissolution during the OER renders this material impractical for regenerative fuel cell applications. To address Ag stability during AEMFC load cycles, accelerated stress tests (ASTs) in O2-saturated solutions are carried out in rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) setups. Besides tracking the ORR performance evolution, an ex situ long-term Ag dissolution study is performed. Moreover, morphological changes in the catalyst/support are tracked by identical-location transmission electron microscopy (RDE-IL-TEM). Voltammetry analysis before and after AST reveals a smaller change in ORR activity for Ag/MC, confirming its higher stability. RRDE results reveal a higher increase in the H2O2 yield for Ag/VC after the ASTs. The RDE-IL-TEM measurements demonstrate different degradation processes that can explain the changes in the long term performance. The results in this work point out that the stability of carbon-supported Ag catalysts depends strongly on the morphology of the Ag nanoparticles, which, in turn, can be tuned depending on the chosen carbon support and synthesis method.

Dataset Information

Carbon supported Pd-Cu nanoalloys: support and valence band structure influence on reduction and oxidation reactions.

Publications

Carbon supported Pd-Cu nanoalloys: support and valence band structure influence on reduction and oxidation reactions.

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