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

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 up-scalable top-down approach to produce 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 commercial Pt/C catalyst, at least 2.7-times in terms of specific (~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. Besides, the technique used here red...