Abstract:Rational
design of metal–organic frameworks (MOFs) into
ultrathin two-dimensional (2D) nanosheets with controllable thickness
is significantly attractive but is also a significant challenge. Herein,
the authors report, for the first time, the synthesis of ultrathin
2D nickel-based MOF nanosheets with a thickness of only about 2 nm
via a ligand-assisted controllable growth strategy, which cannot be
acquired from the exfoliation of their bulky counterparts or the conventional
hydrothermal method. The correlation… Show more
“…The Raman spectrum was deconvoluted into four subpeaks, and by calculating the intensity ratio ( I D / I G ) of the D to G peak area, a quantitative description of the crystallinity was given (Figure a and Table S1). , By comparing the degree of crystallization of different samples, it can be seen that the I D / I G ratios of C-NiFe (0.42), C-Ni (0.51), and C-Fe (0.48) are all lower than that of C (0.53), which indicates that the three samples of C-NiFe, C-Ni, and C-Fe all have more graphitic structure. This may be due to the role of Ni and Fe in catalyzing graphitization during carbonization.…”
Section: Resultsmentioning
confidence: 98%
“…The Raman spectrum was deconvoluted into four subpeaks, and by calculating the intensity ratio (I D /I G ) of the D to G peak area, a quantitative description of the crystallinity was given (Figure 2a and Table S1). 43,44 By comparing the degree of crystallization of different samples, it can be seen that the I D /I G ratios of C-NiFe (0. The electrocatalytic ORR and OER performance of the asprepared C, C-Fe, C-Ni, and C-NiFe samples was investigated in alkaline solutions (0.1M KOH aqueous solution) by using a standard three-electrode system, and Pt/C (20 wt %) was used as the benchmark reference.…”
There is an urgent demand for developing highly efficient
bifunctional
electrocatalysts with excellent stability toward the oxygen evolution
and reduction reactions (OER and ORR, respectively) for rechargeable
Zn–air batteries (ZABs). In this work, NiFe nanoparticles encapsulated
within ultrahigh-oxygen-doped carbon quantum dots (C-NiFe) as bifunctional
electrocatalysts are successfully obtained. The accumulation of carbon
layers formed by carbon quantum dots results in abundant pore structures
and a large specific surface area, which is favorable for improving
catalytic active site exposure, ensuring high electronic conductivity
and stability simultaneously. The synergistic effect of NiFe nanoparticles
enriched the number of active centers and naturally increased the
inherent electrocatalytic performance. Benefiting from the above optimization,
C-NiFe shows excellent electrochemical activity for both OER and ORR
processes (the OER overpotential is only 291 mV to achieve 10 mA cm–2). Furthermore, the C-FeNi catalyst as an air cathode
displays an impressive peak power density of 110 mW cm–2, an open-circuit voltage of 1.47 V, and long-term durability over
58 h. The preparation of this bifunctional electrocatalyst provides
a design idea for the construction of bimetallic NiFe composites for
high-performance Zn–air batteries.
“…The Raman spectrum was deconvoluted into four subpeaks, and by calculating the intensity ratio ( I D / I G ) of the D to G peak area, a quantitative description of the crystallinity was given (Figure a and Table S1). , By comparing the degree of crystallization of different samples, it can be seen that the I D / I G ratios of C-NiFe (0.42), C-Ni (0.51), and C-Fe (0.48) are all lower than that of C (0.53), which indicates that the three samples of C-NiFe, C-Ni, and C-Fe all have more graphitic structure. This may be due to the role of Ni and Fe in catalyzing graphitization during carbonization.…”
Section: Resultsmentioning
confidence: 98%
“…The Raman spectrum was deconvoluted into four subpeaks, and by calculating the intensity ratio (I D /I G ) of the D to G peak area, a quantitative description of the crystallinity was given (Figure 2a and Table S1). 43,44 By comparing the degree of crystallization of different samples, it can be seen that the I D /I G ratios of C-NiFe (0. The electrocatalytic ORR and OER performance of the asprepared C, C-Fe, C-Ni, and C-NiFe samples was investigated in alkaline solutions (0.1M KOH aqueous solution) by using a standard three-electrode system, and Pt/C (20 wt %) was used as the benchmark reference.…”
There is an urgent demand for developing highly efficient
bifunctional
electrocatalysts with excellent stability toward the oxygen evolution
and reduction reactions (OER and ORR, respectively) for rechargeable
Zn–air batteries (ZABs). In this work, NiFe nanoparticles encapsulated
within ultrahigh-oxygen-doped carbon quantum dots (C-NiFe) as bifunctional
electrocatalysts are successfully obtained. The accumulation of carbon
layers formed by carbon quantum dots results in abundant pore structures
and a large specific surface area, which is favorable for improving
catalytic active site exposure, ensuring high electronic conductivity
and stability simultaneously. The synergistic effect of NiFe nanoparticles
enriched the number of active centers and naturally increased the
inherent electrocatalytic performance. Benefiting from the above optimization,
C-NiFe shows excellent electrochemical activity for both OER and ORR
processes (the OER overpotential is only 291 mV to achieve 10 mA cm–2). Furthermore, the C-FeNi catalyst as an air cathode
displays an impressive peak power density of 110 mW cm–2, an open-circuit voltage of 1.47 V, and long-term durability over
58 h. The preparation of this bifunctional electrocatalyst provides
a design idea for the construction of bimetallic NiFe composites for
high-performance Zn–air batteries.
“…37,38 Furthermore, regarding the hydrogen bonding interaction and HMTA as the linker, and the center metal in Cu-BDC-HMTA as 6-connected node, the supramolecular constructure can be simplified to a pcu topology with the point symbol of {4 12 •6 3 } (Figure 1e). 39,40 Detailed crystallographic data of Cu-BDC-HMTA are listed in Tables S1 and S2.…”
Section: ■ Results and Discussionmentioning
confidence: 99%
“…While Cu (2) is six-coordinated with an octahedral geometry structure and connected with one N atom and five O atoms, two O atoms are from two BDC ligands, the other two O atoms are provided by the same nitrate group, and the last one O is from the coordinate water molecule as well as one N atom provided by the N-donor ligand. As shown in Figure d, adjacent layers can be stacked into a supramolecular architecture through hydrogen-bond interactions. , Furthermore, regarding the hydrogen bonding interaction and HMTA as the linker, and the center metal in Cu-BDC-HMTA as 6-connected node, the supramolecular constructure can be simplified to a pcu topology with the point symbol of {4 12 ·6 3 } (Figure e). , Detailed crystallographic data of Cu-BDC-HMTA are listed in Tables S1 and S2.…”
Section: Resultsmentioning
confidence: 99%
“…The peaks located at 530.3, 531.2, and 532.4 eV are assigned to the Cu–O, oxygen vacancy regions, and adsorbed water of the as-prepared samples, , respectively. Moreover, in the deconvoluted spectrum of C 1s, the four peaks located at about 288.1, 286.3, 285.0, and 284.0 eV correspond to carboxyl, carbonyl, and C–N bonds and graphitic carbon, , respectively (Figure i).…”
Delicate design and bottom-up synthesis of hollow nanostructures
for oxygen evolution electrocatalysts is a promising way to accelerate
the reaction kinetics of overall water splitting. Herein, an efficient
and versatile strategy for the controllable preparation of Pd–Cu
alloy nanoparticles encapsulated in carbon nanopillar arrays (PD–Cu@HPCN)
is developed. Core–shell structured MOF@imidazolium-based ionic
polymers (ImIPs) have been prepared and adopted as a template, along
with the decomposition of the inner Cu–MOFs when an anion exchange
occurs between sodium tetrachloropalladate in solution and bromides
in the external ImIP shell. Pd nanoparticles will be highly dispersed
in the resulting Pd–Cu@HO-ImIP array, and subsequent topotactic
transformation generates Pd–Cu@HNPC. No hazardous reagents
or tedious steps are used to remove the inner Cu–MOF templates
in contrast to the traditional top-down methods. Remarkably, the Pd–Cu@HPCN
catalyst possesses outstanding oxygen evolution reaction (OER) activity,
including small overpotential with 10 mA cm–2 at
an overpotential of 188 mV, a large double layer capacitance (73.8
mF cm–2), and high stability (20 h). This simple,
green, and efficient synthesis methodology represents a new way to
design metal alloys for OER electrocatalysts or other electrocatalytic
devices.
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