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(1)zinc-iron-embedded 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.