The increasing need
for clean and sustainable energy inspires researchers
to explore low-cost nonprecious metal electrocatalysts for advanced
energy storage and conversion. Herein, we develop a reactive template
route to fabricate a high-efficiency oxygen reduction reaction (ORR)/oxygen
evolution reaction (OER)/hydrogen evolution reaction (HER) trifunctional
electrocatalyst (CoFe/NH-C NS) via pyrolyzing the mixture
containing CoFe-layered double hydroxide@glucosaminoglycan (CoFe-LDH@p-Glu)
and urea/dicyandiamide. In this strategy, the CoFe-LDH not only provides
a well-defined two-dimensional template to form carbon NSs but also
employs a well-distributed CoFe precursor to form uniform CoFe nanoparticles
(NPs). Such a synthetic strategy has been demonstrated effective to
controllably fabricate the special nanostructure with metal NPs embedded
in N-doped carbon NSs and favorable exposure of active sites, leading
to a strong synergistic effect between CoFe and N-doped carbon NSs
and abundant electrocatalytic active sites for energy electrocatalysis.
CoFe/NH-C NS exhibits superior ORR performances to Pt/C
with more positive half-wave potential (844 mV for CoFe/NH-C NS vs 832 mV for Pt/C), longer stability, and better methanol
tolerance in alkaline conditions. Furthermore, CoFe/NH-C
NS displays an identical current density to commercial RuO2 at 1.8 V (vs RHE) toward OER and a remarkable electrocatalytic property
toward HER in alkaline conditions. This work presents fresh strategies
for the design and fabrication of high-performance carbon-based energy
materials.
An oxide catalyst plays an important role in environmental
catalysis.
Metal chlorides are widely used as precursors in the preparation of
oxide catalysts. However, residual chlorine usually influences the
performance of catalysts. In this work, we systematically investigate
the influence and efficient removal of chlorine residue on the Co3O4 catalyst in CO oxidation by control experiments
and related characterizations. Compared to the cobalt nitrate-derived
catalyst, the cobalt chloride-derived Co3O4 catalyst
shows a significant improvement in catalytic activity after being
washed with water, suggesting that residual chlorine exerts a detrimental
effect on the Co3O4 catalyst in CO oxidation.
Further investigations show that residual chlorine inhibits the activity
of surface oxygen species as well as blocks the active sites. It is
noteworthy that residual chlorine cannot be efficiently removed before
the calcination because of the strong interactions between the chloride
anions and cobalt precursor. In addition, the washed chloride-derived
catalyst even shows a better catalytic performance than the nitrate-derived
one because of more active sites that are exposed on the surface with
the removal of residual chlorine. More importantly, most of the commercial
Co3O4 samples are found to be seriously poisoned
by chlorine. Hence, efficient elimination of residual chlorine is
very important and should be undertaken before the use of catalysts
in the case of using chlorides as precursors.
The construction
of earth-abundant and non-noble-metal-based oxygen
evolution reaction (OER) electrocatalysts that could work effectively
with long-term stability in alkaline electrolyte is of primary significance,
but still challenging. Herein, we propose a novel OER electrocatalyst
based on trimetallic (Co/Ni/Cu) hydroxyphosphate with unique nanosheet
array architecture grown on nickel foam, aiming at designing the non-noble-metal-based
OER electrocatalyst with both excellent durability and catalytic activity.
The copper hydroxyphosphate was employed with a two-step hydrothermal/ion-exchange
strategy for the fabrication of the target material. Serving as an
OER electrocatalyst, the obtained trimetallic (Co/Ni/Cu) hydroxyphosphate/Ni
foam composite demonstrates excellent electrocatalytic activity with
an low overpotential of 370 mV at 50 mA/cm2 (vs 523 mV
of RuO2) and outstanding stability of 45 h (vs 8.5 h of
RuO2) in 0.1 M KOH.
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