Examinando por Autor "Morales, M. V."

Mostrando 1 - 1 de 1
  • Miniatura
    Publicación
    Cu and Pd nanoparticles supported on a graphitic carbon material as bifunctional HER/ORR electrocatalysts
    (ELSEVIER, 2020-11-01) Nunes, Marta S.; Fernandes, Diana M.; Morales, M. V.; Rodríguez Ramos, Inmaculada; Freire, Cristina; Guerrero Ruiz, Antonio R; https://orcid.org/0000-0002-0460-451X; https://orcid.org/0000-0001-5263-2737; https://orcid.org/0000-0003-2834-0296; https://orcid.org/0000-0003-4622-6008; https://orcid.org/0000-0003-1848-5985
    The development of efficient, available and robust substitutes for the Pt-based electrocatalysts is very important for a sustainable energetic future. Herein, we report a series of composites based on Cu, Pd and Cu-Pd nanoparticles (NPs) supported on high surface area graphite (HSAG), as electrocatalysts for the energy-related reduction reactions – oxygen reduction (ORR) and hydrogen evolution (HER) reactions. All the composites showed interesting ORR electrocatalytic activities in alkaline medium. The Pd/HSAG and Cu-Pd/HSAG composites exhibited the most promising performances, with onset potentials of 0.84 and 0.91 V and current densities of jL, 0.3 V, 1600 rpm=−3.5 and −4.2 mA cm−2, respectively. All the composites showed selectivity for the 4-electron process and Tafel slopes in the range 48–77 mV dec−1. The metal/HSAG composites revealed a great tolerance to methanol and moderate electrochemical stability. In highly acidic medium (0.5 mol dm−3 H2SO4, pH=0.3) only the Cu-Pd/HSAG and Pd/HSAG electrocatalysts presented electrocatalytic activity toward HER, with relative low overpotentials (η10=0.145 and 0.063 V, respectively), small Tafel slopes (75 and 42 mV dec−1) and similar exchange current densities (0.43 and 0.57 mA cm−2). These electrocatalysts also showed moderate electrochemical stability, in particular Cu-Pd/ HSAG for which overpotential only changed between 0.033 and 0.038 V for j=40mAcm−2. The results showed that only small loading of Pd NPs (1 wt.% Pd) was able to improve significantly the ORR/ HER electrocatalytic activity, which is a very important outcome to rationalize the design of efficient and costeffective electrocatalysts in future.