Interface engineering of supported palladium electrocatalyst with covalent organic polymer towards oxygen reduction reaction.

Interface engineering is an important strategy to improve the oxygen reduction reaction (ORR) performance of metal-based electrocatalysts. However, how to develop efficient and abundant interface is still a challenge. Herein, the three-dimensional mesoporous metal oxide-supported Pd-based catalyst was prepared and its ORR activity was further improved through the interfacial modification with microporous covalent organic polymer. Due to the meso/microporous structure and optimized organic-inorganic interface, the as-obtained catalyst could provide abundant active sites and suitable electronic structure, which makes it as a superior catalyst toward alkaline ORR. The surface modified Pd catalyst shows an improved half-wave potential (E1/2) from 0.84 V to 0.86 V and an improved limiting current density (JL) from 5.8 mA cm-2 to 6.0 mA cm-2. Moreover, the developed catalyst has excellent methanol tolerance and stability during the long-time cycling. When it was used as cathodic electrocatalyst in zinc-air battery, a peak power density of 106 mW cm-2 could be achieved and the battery maintains excellent stability during cycling tests over 45 h, which is better than the benchmarked commercial Pt/C catalyst. This study provides an efficient interface engineering strategy for constructing active and stable electrocatalysts, which may be useful in ORR and other energy-related conversions.