2 research outputs found
Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium
Developments of high-performance cost-effective electrocatalyts that can replace Pt catalysts have been a central theme in polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). In this direction, nitrogen-doped carbon nanostructures free of metallic components have attracted particular attention. Here we show that directing graphitic carbon nitride frameworks into mesoporous architecture can generate a highly promising metal-free electrocatalyst for an oxygen reduction reaction (ORR) in an acidic medium. The ordered mesoporous carbon nitride (OMCN) was synthesized with a nanocasting strategy using ordered mesoporous silica as a template. A variety of characterizations revealed that the OMCN is constructed with graphitic carbon nitride frameworks and ordered arrays of uniform mesopores. The OMCN showed significantly enhanced electrocatalytic activity for ORR compared to bulk carbon nitride and ordered mesoporous carbon in terms of the current density and onset potential. A high surface area and an increased density of catalytically active nitrogen groups in the OMCN appear to contribute concomitantly to the enhanced performance of the OMCN. Furthermore, the OMCN exhibited superior durability and methanol tolerance to a Pt/C catalyst, suggesting its widespread utilization as an electrocatalyst for PEMFCs and DMFCs
Polyaniline/Polyoxometalate Hybrid Nanofibers as Cathode for Lithium Ion Batteries with Improved Lithium Storage Capacity
Hybrid nanofibers of polyaniline/polyoxometalate
are synthesized
via a facile interfacial polymerization method for the first time,
and evaluated as a cathode material for lithium ion batteries. The
hybrid nanofibers with 100 nm diameter consisted of phosphomolybdic
acid polyanion, [PMo<sub>12</sub>O<sub>40</sub>]<sup>3–</sup>, and polyaniline matrix. Their 1D geometry improves the utilization
of electrode materials and accommodates the volume change during cycling,
which enables the significant improvement in lithium storage capacity
and capacity retentions. The phosphomolybdic acid polyanions not only
exhibit a large theoretical capacity of about 270 mAh g<sup>–1</sup>, but also reduce the charge transfer resistance of electrode leading
to the enhanced reversible capacity and rate capability. The polyaniline/polyoxometalate
nanofibers delivered a remarkably improved electrochemical performance
in terms of lithium storage capacity (183.4 mAh g<sup>–1</sup> at 0.1C rate), cycling stability (80.7% capacity retention after
50 cycles), and rate capability (94.2 mAh g<sup>–1</sup> at
2C rate) compared to polyaniline nanofibers and bulk polyaniline/polyoxometalate
hybrid