Pulse microwave synthesis of palladium catalysts on graphene electrodes for proton exchange membrane fuel cells

Nanostructured palladium (Pd) dispersed on graphene nanosheets (GNs) has been fabricated using a pulse microwave-assisted polyol (MP) synthesis approach at different pH values of 7, 9, and 11. The highly crystalline Pd can be obtained at a short time of 10 min under pulse microwave irradiation. The electrocatalytic activity and stability of Pd@GN catalyst electrodes at different pH values are well examined using cyclic voltammetry, electrochemical impedance spectroscopy, and single-cell test at 30–75 °C. The electrochemically active surface area and surface utilization of Pd@GN catalyst prepared at pH = 9 can be attained as high as 72.2 m2 g−1 and 94.7%, respectively. This improved catalytic activity is attributed to good dispersibility of the Pd nanocatalysts onto the surface of GNs, which render multiple roles for the dispersion of Pd clusters, ionic diffusion, and charge transfer. The single cell equipped with the Pd@GN catalysts exhibits a maximal power density of 1.75 kW g−1 at 75 °C. Accordingly, this MP approach offers a potential way to develop high-performance catalyst electrodes for fuel cell applications.