Abstract
Non-precious transition metals encapsulated in nitrogen-doped carbon nanotubes or between graphene layers are promising electrocatalysts for the oxygen evolution reaction (OER), which is part of a green hydrogen production process. Recently, FeNi3 nanoparticles encapsulated by one layer of nitrogen-doped carbon (NC) denoted FeNi3@NC were experimentally reported to be highly active.
However, the electrocatalytic performance of such system has not been optimized and the influences of factors such as the thickness and defects of N-doped carbon layers on the catalytic activity remain unknown. In this work, we report that FeNi3@NC is more catalytically active than the same system covered by three N-doped carbon layers, and that the presence of defects in the N-doped layer only has a minor influence on the OER activity.
We used density functional theory (DFT) calculations with dispersion correction based on a slab model of thermodynamically stable fcc(111) surfaces of FeNi3. We found that the mechanism depends on the charge transfer from FeNi3 to NC layers, which can be tuned by adjusting the thickness of the carbon layers.
Our results agree well with the available experimental over-potentials reported in literature for NC as well as FeNi3@NC.