Core−Shell Nanocomposites Based on Gold Nanoparticle@Zinc− Iron-Embedded Porous Carbons Derived from Metal−Organic Frameworks as Efficient Dual Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions

Core−shell nanocomposites based on Au nanoparticle@zinc−ironembedded porous carbons (Au@Zn−Fe−C) derived from metal−organic frameworks were prepared as bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). A single Au nanoparticle of 50−100 nm in diameter was encapsulated within a porous carbon shell embedded with Zn−Fe compounds. The resulting Au@Zn−Fe−C hybrids exhibited apparent catalytic activity for ORR in 0.1 M KOH (with an onset potential of +0.94 V vs RHE, excellent stability and methanol tolerance) and for HER as well, which was evidenced by a low onset potential of −0.08 V vs RHE and a stable current density of 10 mA cm−2 at only −0.123 V vs RHE in 0.5 M H2SO4. The encapsulated Au nanoparticles played an important role in determining the electrocatalytic activity for ORR and HER by promoting electron transfer to the zinc−iron-embedded porous carbon layer, and the electrocatalytic activity was found to vary with both the loading of the gold nanoparticle cores and the thickness of the metal−carbon shells. The experimental results suggested that metal-embedded porous carbons derived from metal−organic frameworks might be viable alternative catalysts for both ORR and HER.