Issue 30, 2020

Single-atom-sized Ni–N4 sites anchored in three-dimensional hierarchical carbon nanostructures for the oxygen reduction reaction

Abstract

The four-electron (4e) oxygen reduction reaction (ORR) is a basic reaction in fuel cells and metal–air batteries, but its wide use requires the development of efficient and inexpensive catalysts. This work demonstrates that single-atom-sized Ni–N4 sites embedded in three-dimensional and hierarchically structured carbon (NiN4–C) exhibit a high catalytic activity for the ORR under alkaline conditions, in which their activity is better than, or at least as high as, that of commercial Pt/C catalysts. The catalyst is synthesized by simply pyrolyzing a mixture of nickel salt and EMIM-dca (1-ethyl-3-methylimidazolium dicyanamide). The product comprises many single Ni atom active sites (the content of Ni atoms in the catalyst is ∼4.2 ± 0.4 wt% as estimated by ICP-OES), in which each Ni atom is coordinated with four N atoms through the formation of a Ni–N4 planar configuration. Both theoretical simulations and electrochemical measurements demonstrate that the catalyst has a high 4e selectivity, i.e., it facilitates an effective 4e ORR with a limiting 2e reaction. Moreover, when it is integrated into a Zn–air battery, the catalyst shows a maximum power density of ∼95 mW cm−2, similar to the power density of Pt/C catalysts. The results are helpful for understanding and analyzing the catalytically active sites of carbon-supported single metal atom catalysts.

Graphical abstract: Single-atom-sized Ni–N4 sites anchored in three-dimensional hierarchical carbon nanostructures for the oxygen reduction reaction

Supplementary files

Article information

Article type
Paper
Submitted
26 May 2020
Accepted
06 Jul 2020
First published
07 Jul 2020

J. Mater. Chem. A, 2020,8, 15012-15022

Single-atom-sized Ni–N4 sites anchored in three-dimensional hierarchical carbon nanostructures for the oxygen reduction reaction

Z. Cai, P. Du, W. Liang, H. Zhang, P. Wu, C. Cai and Z. Yan, J. Mater. Chem. A, 2020, 8, 15012 DOI: 10.1039/D0TA05326K

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