Investigation of Nb2O5/Graphene Supported Platinum-Cobalt Nanocomposite as Electrocatalyst for the Alkaline Alcohols Fuel Cells

In the present work, niobium oxide/graphene supported PtCo catalyst with the Pt:Co molar ratio 1:7 (denoted as PtCo(1:7)Nb₂O₅/GR) was fabricated by means of the rapid microwave heating polyol method. The surface morphology, structure and composition of the synthesized catalyst were examined by transmission electron microscopy, X-ray diffraction and inductively coupled plasma optical emission spectroscopy. The electrocatalytic activity of the synthesized catalyst towards the oxidation of alcohols – ethanol, methanol and ethylene glycol in an alkaline medium was investigated by means of cyclic voltammetry and chronoamperometry.

It has been determined that the Pt loadings was 0.285 mg Pt cm^–2 in the synthesized PtCo(1:7)Nb₂O₅/GR catalyst. For comparison, the bare commercial Pt/C (Sigma-Aldrich) catalyst with 10% wt. Pt with the Pt loading of 0.385 mg Pt cm^–2 was used. The electroactive surface areas (ESAs) of the prepared and commercial catalysts were determined from the cyclic voltammograms of PtCo(1:7)Nb₂O₅/GR and Pt/C catalysts recorded in a deaerated 0.5 M H₂SO₄ solution at a sweep rate of 50 mV s^–1by calculating the charge associated with the hydrogen adsorption.

According to the data of TEM analysis, the Pt nanoparticles of ca. 1-2 nm in size were successively deposited onto the surface of graphene nanosheets.

It has been found that niobium oxide/graphene supported PtCo catalyst with the Pt:Co molar ratios 1:7 show an enhanced electrocatalytic activity towards the oxidation of alcohols in an alkaline medium as compared with that of 10% wt. Pt implicated commercial Pt/C catalyst. Alcohols oxidation current densities were found to be ca. 3 – 40 times higher at the PtCo(1:7)Nb₂O₅/GR catalyst in comparison with those at the commercial Pt/C catalyst. The prepared catalyst seem to be a promising anodic material for direct alcohols fuel cells.

Acknowledgement

Postdoctoral fellowship is being funded by European Union Structural Funds project ”Postdoctoral Fellowship Implementation in Lithuania”.