Co–Fe-modified nitrogen-doped multi-walled carbon nanotubes for alkaline hydrogen evolution: performance and structure–performance correlations

Abstract

Developing earth-abundant hydrogen evolution reaction (HER) electrocatalysts that combine high activity with robust stability is critical for practical alkaline water electrolysis. Herein, nitrogen-doped multi-walled carbon nanotubes were employed as conductive tubular scaffolds to construct Fe-NCNT, Co-NCNT, as well as CoFe-NCNT through pyrolysis of metal–organic coordination precursors. Their morphology, crystalline structure, surface chemistry, defect features, and textural properties were systematically examined through SEM, TEM, XRD, XPS, Raman spectroscopy, alongside N 2 adsorption–desorption measurements. Meanwhile, 1 M KOH was used to evaluate their HER performance. CoFe-NCNT preserves a well-defined hollow nanotubular architecture while exhibiting a higher defect density and larger specific surface area, which favor the formation and exposure of Co–N x /Fe–N x dual active sites. As a result, for CoFe-NCNT, the overpotential needed to achieve 10 mA cm –2 is as low as 30.2 mV, and the Tafel slope is 68.4 mV dec −1 , outperforming Fe-NCNT, Co-NCNT, and commercial Pt/C, together with good catalytic stability. From the above findings, coupling Co and Fe sites into the N-doped carbon nanotube framework can effectively enhance alkaline HER catalysis.