Dual templating preparation approach for hierarchical and highly ordered PEM fuel cell electrode Mengnan Wang 1,2 , Ifan.E.L. Stephens 2 , Maria Magdalena Titirici 1 * 1 Department of Chemical Engineering, Imperial College London, UK, 2 Department of Materials, Imperial College London, UK Carbon materials with defined nanostructures are of great interest for the electrode development of proton exchange membrane fuel cell (PEMFC), where the catalysts are currently dependent on Pt deposited on carbon due to its well acknowledged supreme activity and stability in acidic environment. To make PEMFC more widely available, the catalysts support with optimal porosity is believed to enhance the electrode performance by providing good accessibility of the active sites and efficient triple-phase interfaces. In a previous project, we have developed highly ordered mesoporous carbon from biomass and observed enhanced oxygen reduction reaction (ORR) activity. Comprehensive study with gas sorption analysis and X-ray absorption spectroscopy has demonstrate the ORR activity was governed by the optimal ionomer/catalysts interaction. Scaling up from the optimal mesopores, a hierarchical carbon structure is developed to facilitate the delivery of gas reactants to the active sites as well as the removal of produced water. Here we describe a general dual templating strategy for the synthesis of highly ordered hierarchical carbon having uniform but tuneable diameters (mesopores of 4-40 nm and macropores of 200-400 nm). Lignin, which is an abundant natural biopolymer making up to 25% of plant biomass, is chosen as the carbon precursor. The defined nanostructures are formed by using polystyrene as hard templates and amphiphilic block copolymers as soft templates. Both templates are easily removed during the carbonisation process leaving a freestanding carbon framework. The resulting material supports a high dispersion of platinum nanoparticles, demonstrating outstanding ORR performance under gas diffusion half-cell.
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