Tailoring Pt-Alloy Cluster Nanoparticles for Enhanced Electrocatalytic Activity

Polymer electrolyte membrane fuel cell, PEMFC is an electrochemical energy conversion device that has the potential to be an alternative to internal combustion engines. However, the complexity and slow oxygen reduction reaction (ORR) kinetics on the catalyst surface are among the most limiting factors in the energy conversion efficiency of the state-of-the-art PEMFCs. For large scale and wider application of fuel cells it is estimated that an approximately five-fold reduction in the amount of Pt-loading in membrane-electrode assembly (MEA) to << 0.15mgPt/cm(2) MEA is envisaged, while maintaining high power density at high cell voltage. In this work, we demonstrate a facile fabrication method using biomimetic protein directed self-organization followed by reducing of the corresponding precursor salt/s to prepare shape and size controlled Pt and Pt-alloy nanoparticles (<< 5nm) with precise control over size, shape, compositions and morphology. It is demonstrated that the Pt-heterostructures so produced are highly active towards ORR and methanol oxidation reaction; electrochemical stability is significantly better than commercially available catalytic systems (Pt supported on carbon black). The improvement in catalytic activity is attributed to the narrow size distribution, high surface area of Pt NP and porous nature of the catalyst system.