Cu and Pd nanoparticles supported on a graphitic carbon material as bifunctional HER/ORR electrocatalysts

• Published in: Catalysis today 2020-11, Vol.357, p.279-290
• Main Authors: Nunes, Marta, Fernandes, Diana M., Morales, M.V., Rodríguez-Ramos, I., Guerrero-Ruiz, A., Freire, Cristina
• Format: Article
• Language: English
• Subjects: Bifunctionality; Copper nanoparticles; Hydrogen evolution reaction; Oxygen reduction reaction; Palladium nanoparticles
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2019.04.043

[Display omitted] •Cu and Pd NPs supported on HSAG were tested as bifunctional ORR/HER electrocatalysts.•The composites showed good electrocatalytic performances and an moderate durability.•A small loading of Pd NPs was able to improve the ORR/HER electrocatalytic activity. 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 = 40 mA cm−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 cost-effective electrocatalysts in future.