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  • Title: Regulating Hollow Carbon Cage Supported NiCo Alloy Nanoparticles for Efficient Electrocatalytic Hydrogen Evolution Reaction.
    Author: Qi B, Chang W, Xu Q, Jiang L, An S, Chu JF, Song YF.
    Journal: ACS Appl Mater Interfaces; 2023 Mar 08; 15(9):12078-12087. PubMed ID: 36843294.
    Abstract:
    The NiCo alloy is one of the most promising alternatives to the noble-metal electrocatalysts for the hydrogen evolution reaction (HER); however, its performance is largely restricted by insufficient active sites and low surface area. Here, we fabricated a hierarchical hollow carbon cage supported NiCo alloy (denoted as HC NiCo/C) and a bulk NiCo alloy (denoted as NiCo) by reduction of a partially ZIF-67 etched ZIF-67@NiCo-LDH (LDH = layered double hydroxide) precursor and a fully ZIF-67 etched NiCo-LDH precursor, respectively. The as-prepared HC NiCo/C, in which the Ni29Co71 alloy nanocrystals with an average 6 nm size were encapsulated in graphitic carbon layers, provided a vastly increased electrochemically active surface area (ca. 13 times than the NiCo) and abundant catalytic active sites, which resulted in a higher HER performance with an overpotential of 99 mV than the 198 mV for NiCo at 10 mA cm-2. Detailed experimental results suggested that only the HC NiCo/C possessed the active alloy surface composed of unsaturated Ni0 and Co0 atoms, and both the metal-support interaction and alloying effect influenced the electronic structure of Co and Ni in HC NiCo/C, whereas the NiCo exhibited pure Ni surface. Theoretical calculations further revealed the Ni29Co71 alloy surface in HC NiCo/C possessed the appropriate adsorption energy of the intermediate state (adsorbed H*). This work provided new insight into the construction of the stable small-sized bimetallic alloy nanocatalysts by regulating the reduction precursors.
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