Graphene-cobaltite-Pd hybrid materials for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cellsElectronic supplementary information (ESI) available: Results of deconvolution of the Co 2p X-ray photoelectron spectra, Table S1. See DOI: 10.1039/c3cp53880j

Hybrid materials comprising of Pd, MCo 2 O 4 (where M = Mn, Co or Ni) and graphene have been prepared for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells. Structural and electrochemical characterizations were carried out using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, chronoamperometry and cyclic, CO stripping, and linear sweep voltammetries. The study revealed that all the three hybrid materials are active for both methanol oxidation (MOR) and oxygen reduction (ORR) reactions in 1 M KOH. However, the Pd-MnCo 2 O 4 /GNS hybrid electrode exhibited the greatest MOR and ORR activities. This active hybrid electrode has also outstanding stability under both MOR and ORR conditions, while Pt- and other Pd-based catalysts undergo degradation under similar experimental conditions. The Pd-MnCo 2 O 4 /GNS hybrid catalyst exhibited superior ORR activity and stability compared to even Pt in alkaline solutions. Linear sweep voltammograms of Pd-5MnC/GNS, Pt/NC and Pt/GNS at a fixed catalyst loading (0.60 mg cm −2 ) in O 2 -saturated 1 M KOH; scan rate = 2 mV s −1 ; rotation = 1600 rpm and T = 25 °C.