Defects and morphology engineering
is a serviceable strategy to
boost the electrochemical energy conversion and storage performance
of carbon-based materials. In this study, nitrogen/sulfur codoped
carbon nanotubes (NS-CNTs) were first obtained via the pyrolysis of
presynthesized polyaniline nanotubes with micelles composed of methyl
orange and ferric chloride acting as the soft template. Furthermore,
intrinsic carbon defects and mesopores were introduced to obtain etched
NS-CNTs (ENS-CNTs) composites by ammonia etching. The rational combination
of intrinsic/extrinsic defects and porous nanotube morphology features
is beneficial to the oxygen reduction reaction (ORR) and sulfur reduction
reaction (SRR) performances of the ENS-CNTs electrode. The coexistence
of intrinsic carbon defects and extrinsic N/S dopants can create massive
catalytically active sites for electrochemical processes, while the
porous one-dimensional nanotube-like carbon framework is responsible
for accessibility of catalytic active sites, species hosting, electrical
conductivity, mass transport, and stability. Consequently, the ENS-CNTs-30
(where 30 represents the corresponding etching time in minutes) electrode
for ORR displayed a high half-wave potential of 859 mV vs RHE, a diffusion
limiting current density of 6.65 mA cm–2, admirable
stability, and methanol tolerance. The solid Zn–air battery
(ZAB) assembled with ENS-CNTs-30 as the active material for the air
cathode revealed remarkable power density (137 mW cm–2) and specific capacity (1467.4 mAh g–1
Zn). Meanwhile, the ENS-CNTs-30 electrode for SRR also demonstrated
ameliorative lithium–polysulfide (LiPS) trapping capability
and Li2S deposition kinetics. The lithium–sulfur
battery (LSB) with ENS-CNTs-30 as sulfur host material unfolded initial
capacities of 1100 and 883 mAh g–1 at 0.2 and 2
C, respectively, and a capacity retention ratio of 82.0% after 200
cycles at 0.2 C. This work provides a feasible strategy for defects
and morphology engineering of multifunctional carbon-based catalysts
in electrochemical energy conversion and storage fields.