Electrocatalytic enhancement of platinum and palladium metal on polydopamine reduced graphene oxide support for alcohol oxidation

The objective of our work is to improve low-temperature fuel cell catalysts by increasing the surface area to augment the efficiency of catalytic reactions. Reduced graphene oxide (rGO) supports were prepared by adding N-containing derivatives of polydopamine (PDA) and loading of Pt and Pt-based metal alloy nanoparticles were accomplished for catalyst preparation. To study the effects of surface modification on catalyst activity, the GO surfaces modified by addition of PDA (PDA-rGO) were richer in oxygen and nitrogen-containing functional groups, which reduced the number of graphene defects. Reduction of metals (M = Pt, Pd, PtxPdy where x and y = 1-3) by NaBH4 produced M/GO (metal on GO) and M/PDA-rGO (metal on PDA-rGO) catalysts. Examination of morphology and chemical composition confirmed that the existence of particle size on M/PDA-rGO catalysts was smaller than that on M/GO catalysts in agreement with calculated electrochemically active surface areas (ECSA). Electrochemical analysis was conducted to evaluate the catalyst activity and stability. The prepared catalysts had significantly greater surface areas as a result of association between the metal nanoparticles and the oxygen and nitrogen functional groups on the rGO supports. The catalysts also exhibited lower onset potentials and greater current intensities, I-f/I-b values, and long-term stabilities for methanol and ethanol oxidation compared with those of commercial PtRu/C. Moreover, the diameter of the Nyquist plot of the catalysts on PDA-rGO were smaller than that of the catalysts M/GO. The results suggest that variation of the PtxPdy atomic ratio on carbon nanocomposites is an encouraging means of enhancing electrocatalytic performance in direct alcohol fuel cell applications. (C) 2018 Elsevier Inc. All rights reserved.