Collaborative Anchoring of Pt Nanoparticles and Metal Oxide Nanoparticles on N-Doped Carbon as Catalysts for Oxygen Reduction

Platinum (Pt)-based catalysts are the most widely used catalysts for the oxygen reduction reaction (ORR). However, there are still great challenges to overcome in improving catalyst activity and reducing the use of Pt. Herein, catalysts with Pt nanoparticles and metal oxide nanoparticles on N-doped carbon with ultralow Pt loading (<2 wt % Pt), namely, Pt&Fe 2 O 3 /NC and Pt&CoO/NC, are synthesized by a two-step pyrolysis method, in which N-doped carbon is first prepared by pyrolyzing carbon and melamine at 900 °C and Pt nanoparticles and metal oxide nanoparticles are then prepared by pyrolyzing a Pt salt and M(OH) x (M = Fe, Co) at 700 °C. The Pt and metal oxide are uniformly dispersed on the NC, resulting in ultrafine Pt nanoparticles (∼2 nm). Metal oxides regulate the electronic structure of Pt to weaken the binding energy of oxygen. Both Pt&Fe 2 O 3 /NC and Pt&CoO/NC show good ORR catalytic activities in alkaline solution. Pt&Fe 2 O 3 /NC shows the ORR catalytic performance, with the peak potential and half-wave potential at 0.883 and 0.862 V, better than those of Pt&CoO/NC (0.861 and 0.842 V) and Pt/NC (0.856 and 0.838 V) and comparable to that of commercial 20 wt % Pt/C. The ORR mechanism on these two catalysts involves a direct four-electron path. This provides a method for improving the ORR catalytic performance of catalysts with ultralow Pt loading via the joint anchoring of ultrafine Pt by metal oxides and NC, resulting in synergistic interactions.