Issue 19, 2019

Enhancing hydrogen evolution activity by doping and tuning the curvature of manganese-embedded carbon nanotubes

Abstract

Carbon nanotubes (CNTs) incorporated with transition metals have been experimentally found to have great potential in the electrocatalytic hydrogen evolution reaction (HER) in acidic electrolytes. Further elucidating the underlying mechanism determining the HER activity will be helpful to design more highly efficient CNT-based catalysts for the HER. In this work, first-principles density functional theory calculations were performed to investigate the HER on a series of CNTs, substitutionally embedded with atomic Mn (MnCNT(n,n)s, n = 3, 4, 5, 6, 7, and 9) and co-embedded with Mn and double N (MnN2CNT(5,5)). The theoretical calculations suggest that the principal HER active sites on all studied CNT catalysts are the C atoms adjacent to the metal center, and the HER is dominated by the Volmer–Heyrovsky mechanism with the Heyrovsky reaction as the rate-determining step. Tuning the CNT curvatures and embedding heteroatoms (Mn and N) could elevate the C p-band center (εp), weaken the absolute H adsorption free energy (|ΔGH*|), lower the absolute electrode potential (Uabs0), and thus enhance the HER performance. For MnCNT(n,n)s, the HER activity shows a volcano dependence on the surface curvature, peaking at n = 5. Substitutionally doping double N atoms into MnCNT(5,5) could further substantially enhance the HER activity, reflected by its thirtyfold current density relative to platinum. Furthermore, the Uabs0 descriptor, besides ΔGH* and the free energy barrier, could overcome the limitation of εp applied in the same metal-embedded CNTs, extending to describe the HER activity of the transition metal-incorporated CNT system.

Graphical abstract: Enhancing hydrogen evolution activity by doping and tuning the curvature of manganese-embedded carbon nanotubes

Supplementary files

Article information

Article type
Paper
Submitted
13 jun 2019
Accepted
26 avg 2019
First published
27 avg 2019

Catal. Sci. Technol., 2019,9, 5301-5314

Enhancing hydrogen evolution activity by doping and tuning the curvature of manganese-embedded carbon nanotubes

H. Liu, L. Zhao, Y. Liu, J. Xu, H. Zhu and W. Guo, Catal. Sci. Technol., 2019, 9, 5301 DOI: 10.1039/C9CY01174A

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