After carbonization of bamboo nanocellulose aerogels in ammonia gas, the obtained nitrogen-doped carbon nanofiber (N-ACNF) aerogels with a tunable nanostructure were found to be ideal candidates for high-performance anodes in LIBs.
Ultrathin
cellulose nanoribbons were extracted from earth-abundant
biomass using 2,2,6,6-tetramethylpiperidine-1-oxyl-catalyzed (TEMPO-catalyzed)
oxidation and sonication processes. By two TEMPO-oxide systems with
different processing times, TEM and AFM observations indicate the
obtained cellulose nanoribbons (Cel-NRs) with dimensions of 400–800
nm in length, 1.72–2.54 nm in width, and 0.78–2.67 nm
in thickness. The dimension data indicate that the Cel-NRs from the
TEMPO/NaBr/NaClO system are much shorter but contain more cellulose
chains than those from the TEMPO/NaClO/NaClO2 system. Moreover,
these abundant biomass nanoribbons were fabricated from direct pyrolysis
with NH3 activation. The obtained highly active nitrogen-doped
carbon nanoribbons (N-CNRs) and metal-free oxygen reduction reaction
(ORR) electrocatalysts show superb ORR activity (half-wave potential
of 0.71 and 0.73 V versus reversible hydrogen electrode) and high
selectivity (electron-transfer number of 3.26 and 3.74 at 0.8 V),
comparable current density and onset potential (0.906 and 0.926 V),
excellent electrochemical stability (higher than 89.5% and 91.6% after
20 000 potential cycles) in alkaline media, and better resistance
to crossover effects in the ORR. More importantly, when used as a
cathode catalyst for constructing the air electrode of the Zn–air
battery, the N-CNRs exhibit super long-term stability and a capacity
of 587 and 583 mAh g–1 at the discharge current
densities of 5 and 20 mA cm–2, respectively, which
are highly comparable with those of the state-of-the-art Pt/C catalyst
(20 wt % Pt, Hispec 3000). This indicates that our present work is
the first example of using atomically thin carbon nanoribbons as the
metal-free electrocatalyst substitution to Pt for developing high-performance
metal–air batteries from earth-abundant terrestrial plants.
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