Tailoring the Oxygen Reduction Activity of Pt Nanoparticles through Surface Defects: A Simple Top-Down Approach

Abstract

Results from Pt model catalyst surfaces have demonstrated that surface defects, in particular surface concavities, can improve the oxygen reduction reaction (ORR) kinetics. It is, however, a challenging task to synthesize nanostructured catalysts with such defective surfaces. Hence, we present a one-step and upscalable top-down approach to produce a Pt/C catalyst (with ∼3 nm Pt nanoparticle diameter). Using high-resolution transmission electron microscopy and tomography, electrochemical techniques, high-energy X-ray measurements, and positron annihilation spectroscopy, we provide evidence of a high density of surface defects (including surface concavities). The ORR activity of the developed catalyst exceeds that of a commercial Pt/C catalyst, at least 2.7 times in terms of specific activity (∼1.62 mA/cm2Pt at 0.9 V vs the reversible hydrogen electrode) and at least 1.7 times in terms of mass activity (∼712 mA/mgPt), which can be correlated to the enhanced amount of surface defects. In addition, the technique used here reduces the complexity of the synthesis (and therefore production costs) in comparison to state of the art bottom-up techniques.