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

Abstract

Core–shell nanocomposites based on Au nanoparticle@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.

Design Strategies toward Advanced MOF‐Derived Electrocatalysts for Energy‐Conversion Reactions

“…In this regard, Lu et al studied Au NPs@zinc-iron-embedded porous carbons (Au@Zn-Fe-C) derived from MOFs. [83] As shown in Figure 3b, the preparation process involves three steps: i) monodisperse Au NPs with diameter of 50-100 nm were initially synthesized by chemical reduction of HAuCl 4 ; ii) the obtained Au NPs were utilized as heterogeneous nuclei for the epitaxial growth of Zn-Fe-MOF; iii) the Zn-Fe-MOF shell was then pyrolyzed into porous carbons embedded with zinc-iron compounds (ZnFeC) via facile calcination at controlled temperatures. Likewise, the Au core had intimate electronic interactions with the carbon shell, which facilitated electron transfer from the core to the shell, thereby tuning the electron density of the carbon shell and reducing the local work function.…”

“…Adapted with permission. [83] Copyright 2016, American Chemcial Society. c) Schematic illustration of the synthesis process for the ZIF-67-T catalysts.…”

“…[10] For this purpose, rational catalyst design lies in constructing novel electrocatalysts with favourable structures. [33,35,41,64,83,101] Structure engineering is a promising and indispensable strategy to develop improved catalysts in this respect, [102] and plays www.advancedsciencenews.com a critical role in integrating all components to make full use of their functionalities. Until now, a variety of nanostructures or architectures based on MOF-derived materials, such as edge-rich strucutures, [48] core-shell structures, [64,83] sandwich structures, [33] porous nanowire array structures, [35] and threedimensional hierarchical structures, [101] have been synthesized and widely investigated.…”

“…Unsurprisingly, the effect has also been demonstrated by the study reported by Lu et al regarding ORR and HER, in which different metal (Au and Pt) NPs were implanted into MOF-derived shells (Figure 3b). [83] Due to the electron-donor effect, the electrocatalytic activity appears insensitive to different core metals.…”

“…As an important alternative to Pt catalysts, MOF-derived materials exhibit remarkable ORR performance in terms of activity, durability, and tolerance to methanol. [24,[32][33][34][38][39][40][41][42][43][44]47,53,[58][59][60][61][62][63][65][66][67][68][69][70][71][72][73][75][76][77]81,83,97,99,[107][108][109] In particular, some newly developed MOF derivatives achieved highly improved activity that is comparable and even superior to Pt catalysts under identical experimental conditions. Table 1 summarizes the catalytic performances of representative MOF-derived electrocatalysts for the ORR.…”