8 research outputs found
Pt-like Hydrogen Evolution Electrocatalysis on PANI/CoP Hybrid Nanowires by Weakening the Shackles of Hydrogen Ions on the Surfaces of Catalysts
The
search for high active, stable, and cost-efficient hydrogen
evolution reaction (HER) electrocatalysts for water electrolysis has
attracted great interest. The coordinated water molecules in the hydronium
ions will obviously reduce the positive charge density of H<sup>+</sup> and hamper the ability of H<sup>+</sup> to receive electrons from
the cathode, leading to large overpotential of HER on nonprecious
metal catalysts. Here we realize Pt-like hydrogen evolution electrocatalysis
on polyaniline (PANI) nanodots (NDs)-decorated CoP hybrid nanowires
(HNWs) supported on carbon fibers (CFs) (PANI/CoP HNWs-CFs) as PANI
can effectively capture H<sup>+</sup> from hydronium ions to form
protonated amine groups that have higher positive charge density than
those of hydronium ions and can be electro-reduced easily. The PANI/CoP
HNWs-CFs as low-cost electrocatalysts show excellent catalytic performance
toward HER in acidic solution, such as super high catalytic activity,
small Tafel slope, and superior stability
Enhanced Catalytic Activity and Stability of Pt/CeO<sub>2</sub>/PANI Hybrid Hollow Nanorod Arrays for Methanol Electro-oxidation
Here, we designed and fabricated
novel Pt/CeO<sub>2</sub>/PANI
three-layered hollow nanorod arrays (THNRAs) as advanced electrocatalysts
for methanol oxidation by combining the merits of CeO<sub>2</sub>,
PANI, multilayered structure, and hollow nanorod arrays. The synthesized
Pt/CeO<sub>2</sub>/PANI THNRAs exhibit higher electrocatalytic activity
and better stability toward the oxidation of methanol than Pt/PANI
HNRAs, Pt/CeO<sub>2</sub> HNRAs, and commercial Pt/C catalysts. The
enhanced electrocatalytic performance of the Pt/CeO<sub>2</sub>/PANI
THNRAs may be due to the synergistic effects among Pt, CeO<sub>2</sub>, and PANI and the special three-layered hollow nanorod arrays, which
can provide short diffusion paths for electroactive species and high-availability
of electrocatalysts. The facile synthesis method can be considered
as a promising strategy to design low-cost, high-performance electrocatalysts
for fuel cells
Cu<sub>2</sub>O–Cu Hybrid Foams as High-Performance Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media
Here 3D Cu<sub>2</sub>O–Cu hybrid foams are developed as
high-performance electrocatalysts for OER in alkaline solution. The
hybrid foams are composed of Cu<sub>2</sub>O–Cu dendrites with
high surface area and high-speed electronic transmission networks,
and they can provide fast transportation and short diffusion path
for electrolyte and evolved O<sub>2</sub> bubbles. As the special
surface and structure effects, the Cu<sub>2</sub>O–Cu hybrid
foams exhibit low onset overpotential of ∼250 mV, small Tafel
slope of 67.52 mV dec<sup>–1</sup>, and high durability over
50 h at a current density of 10 mA cm<sup>–2</sup> for OER
in alkaline solution. The results of this study may be particularly
beneficial for the development of a type of hybrid porous foam electrocatalysts
for the electrochemical process in which at least one gas-phase is
involved, such as H<sub>2</sub> or O<sub>2</sub> evolution reaction
and O<sub>2</sub> or CO<sub>2</sub> electroreduction reaction
Asymmetric Paper Supercapacitor Based on Amorphous Porous Mn<sub>3</sub>O<sub>4</sub> Negative Electrode and Ni(OH)<sub>2</sub> Positive Electrode: A Novel and High-Performance Flexible Electrochemical Energy Storage Device
Here we synthesize novel asymmetric
all-solid-state paper supercapacitors (APSCs) based on amorphous porous
Mn<sub>3</sub>O<sub>4</sub> grown on conducting paper (NGP) (Mn<sub>3</sub>O<sub>4</sub>/NGP) negative electrode and NiÂ(OH)<sub>2</sub> grown on NGP (NiÂ(OH)<sub>2</sub>/NGP) as positive electrode, and
they have attracted intensive research interest owing to their outstanding
properties such as being flexible, ultrathin, and lightweight. The
fabricated APSCs exhibit a high areal <i>C</i><sub>sp</sub> of 3.05 F/cm<sup>3</sup> and superior cycling stability. The novel
asymmetric APSCs also exhibit high energy density of 0.35 mW h/cm<sup>3</sup>, high power density of 32.5 mW/cm<sup>3</sup>, and superior
cycling performance (<17% capacitance loss after 12 000
cycles at a high scan rate of 100 mV/s). This work shows the first
example of amorphous porous metal oxide/NGP electrodes for the asymmetric
APSCs, and these systems hold great potential for future flexible
electronic devices
α‑Fe<sub>2</sub>O<sub>3</sub>@PANI Core–Shell Nanowire Arrays as Negative Electrodes for Asymmetric Supercapacitors
Highly ordered three-dimensional
α-Fe<sub>2</sub>O<sub>3</sub>@PANI core–shell nanowire
arrays with enhanced specific areal capacity and rate performance
are fabricated by a simple and cost-effective electrodeposition method.
The α-Fe<sub>2</sub>O<sub>3</sub>@PANI core–shell nanowire
arrays provide a large reaction surface area, fast ion and electron
transfer, and good structure stability, which all are beneficial for
improving the electrochemical performance. Here, high-performance
asymmetric supercapacitors (ASCs) are designed using α-Fe<sub>2</sub>O<sub>3</sub>@PANI core–shell nanowire arrays as anode
and PANI nanorods grown on carbon cloth as cathode, and they display
a high volumetric capacitance of 2.02 mF/cm<sup>3</sup> based on the
volume of device, a high energy density of 0.35 mWh/cm<sup>3</sup> at a power density of 120.51 mW/cm<sup>3</sup>, and very good cycling
stability with capacitance retention of 95.77% after 10 000
cycles. These findings will promote the application of α-Fe<sub>2</sub>O<sub>3</sub>@PANI core–shell nanowire arrays as advanced
negative electrodes for ASCs
Design and Synthesis of MnO<sub>2</sub>/Mn/MnO<sub>2</sub> Sandwich-Structured Nanotube Arrays with High Supercapacitive Performance for Electrochemical Energy Storage
We demonstrate the design and fabrication of novel nanoarchitectures
of MnO<sub>2</sub>/Mn/MnO<sub>2</sub> sandwich-like nanotube arrays
for supercapacitors. The crystalline metal Mn layers in the MnO<sub>2</sub>/Mn/MnO<sub>2</sub> sandwich-like nanotubes uniquely serve
as highly conductive cores to support the redox active two-double
MnO<sub>2</sub> shells with a highly electrolytic accessible surface
area and provide reliable electrical connections to MnO<sub>2</sub> shells. The maximum specific capacitances of 937 F/g at a scan rate
of 5 mV/s by cyclic voltammetry (CV) and 955 F/g at a current density
of 1.5 A/g by chronopotentiometry were achieved for the MnO<sub>2</sub>/Mn/MnO<sub>2</sub> sandwich-like nanotube arrays in solution of
1.0 M Na<sub>2</sub>SO<sub>4</sub>. The hybrid MnO<sub>2</sub>/Mn/MnO<sub>2</sub> sandwich-like nanotube arrays exhibited an excellent rate
capability with a high specific energy of 45 Wh/kg and specific power
of 23 kW/kg and excellent long-term cycling stability (less 5% loss
of the maximum specific capacitance after 3000 cycles). The high specific
capacitance and charge–discharge rates offered by such MnO<sub>2</sub>/Mn/MnO<sub>2</sub> sandwich-like nanotube arrays make them
promising candidates for supercapacitor electrodes, combining high-energy
densities with high levels of power delivery
Design of Pd/PANI/Pd Sandwich-Structured Nanotube Array Catalysts with Special Shape Effects and Synergistic Effects for Ethanol Electrooxidation
Low cost, high activity, and long-term
durability are the main
requirements for commercializing fuel cell electrocatalysts. Despite
tremendous efforts, developing non-Pt anode electrocatalysts with
high activity and long-term durability at low cost remains a significant
technical challenge. Here we report a new type of hybrid Pd/PANI/Pd
sandwich-structured nanotube array (SNTA) to exploit shape effects
and synergistic effects of Pd-PANI composites for the oxidation of
small organic molecules for direct alcohol fuel cells. These synthesized
Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity
and durability compared with Pd NTAs and commercial Pd/C catalysts.
The unique SNTAs provide fast transport and short diffusion paths
for electroactive species and high utilization rate of catalysts.
Besides the merits of nanotube arrays, the improved electrocatalytic
activity and durability are especially attributed to the special Pd/PANI/Pd
sandwich-like nanostructures, which results in electron delocalization
between Pd d orbitals and PANI π-conjugated ligands and in electron
transfer from Pd to PANI
Porous Pt-Ni-P Composite Nanotube Arrays: Highly Electroactive and Durable Catalysts for Methanol Electrooxidation
Porous Pt-Ni-P composite nanotube arrays (NTAs) on a
conductive
substrate in good solid contact are successfully synthesized via template-assisted
electrodeposition and show high electrochemical activity and long-term
stability for methanol electrooxidation. Hollow nanotubular structures,
porous nanostructures, and synergistic electronic effects of various
elements contribute to the high electrocatalytic performance of porous
Pt-Ni-P composite NTA electrocatalysts