Enhanced performance of nano-electrocatalysts of Pd and PdCo in neutral and alkaline media

AGUIRRE MARIA DEL CARMEN,; URRETA SILVIA; RIVAS BERNABE; FABIETTI LUIS

JOURNAL OF APPLIED ELECTROCHEMISTRY

SPRINGER

Lugar: Berlin; Año: 2018 vol. 49 p. 1 - 15

0021-891X

Pd and PdCo nanostructures are synthesized by a soft-template route to be applied as electrocatalysts. Distinctive morphologiesare obtained: nanowire-like structures, with mean diameter d = 33 nm (PdNW), forming an entangled network; nanocubes(PdNC) 64 nm in side, and PdCo(NS) nanospheres 60 nm in diameter. Pd:Co feed mol ratios (2:1) and (5:1) are used. Pd andPd?Co nanostructures both crystallize in an fcc structure. A glassy carbon (GC) electrode is then modified with these colloidal dispersions, and further characterized by electrochemical methods. The modified PdNW/GC, PdNC/GC, and PdCoNS/GC electrodes are applied in the oxygen reduction (ORR) and oxygen evolution (OER) reactions, in a phosphate buffer pH 7 and 0.1 M NaOH solution. Voltammetric measurements are consistent with a diffusion controlled mechanism, with a four-electron reduction process in each Pd and PdCo nanoelectrode. Resulting values of kinetic parameters indicate that the relative effectiveness of these solutions in ORR may be ordered as PdCo (5:1)NS/GC ≥ PdCo (2:1)NS/GC > PdNC/GC ≥ PdNW/GC > GC. For the OER, Tafel slopes are measured for the nanosized electrodes in both types of supporting electrolytes.Turnover frequencies estimated in alkaline solution for the OER indicate that nanostructured bimetallic PdCoNS/GC electrodes exhibit better activity than Pd/GC ones.