Authors: Nunes, M; Fernandes, DM; Morales, MV; Rodriguez-Ramos, I; Guerrero-Ruiz, A; Freire, C

Article.
J. Appl. Electrochem.. vol: 49. page: 0021-891X.
Date: JUL. 2019.
Doi: 10.1007/s10800-019-01317-y.

Abstract:
The development of efficient electrocatalysts for the energy-related reactions, based on earth-abundant elements, is extremely important for a sustainable energetic future. Herein, we report the application of Cu nanoparticles supported on undoped and N-doped grapheneCu/GOE and Cu/GOE-u composites, respectivelyas electrocatalysts for the oxygen reduction reaction (ORR). All the materials showed ORR electrocatalytic activities in alkaline medium. The Cu/GOE-u composite exhibited the most promising performance, with an onset potential of 0.84V and a current density of j(L)=-4.4mAcm(-2) (vs. 0.84V and -2.8mA cm(-2) for Cu/GOE), which revealed the great influence of the created Cu-N-x/C active sites on the ORR electrocatalytic activity. The pure GOE-u support showed worse performance than the GOE, demonstrating that the N-doping advantage is not linear and also depends on the type and amount of accessible active sites created. The N-doping allowed an increase in the selectivity for the 4-electron process, resulting in a % of H2O2 produced <25% for Cu/GOE-u (vs. almost 75% for Cu/GOE). Both nanocomposites revealed good tolerance to methanol crossover, and the Cu/GOE-u displayed a moderate long-term electrochemical stability, with current retention of 84% after 20,000s. [GRAPHICS] ..