Quantcast


CURATOR
A pinboard by
Zhengping Zhou

Postdoctoral Associate, Virginia Tech/Chemistry

PINBOARD SUMMARY

Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing

Mesoporous carbon thin films have broad applications in filters, catalyst supports, electronics, gas separators and adsorbents, and energy conversion and storage devices. One of the most important features is the tunable pore size that determine the performance of mesoporous carbon. As a result, a technique that enables precise control of the pore size of mesoporous carbon thin films is highly desirable.

Towards this goal, Dr. Zhengping Zhou and Prof. Guoliang Liu have used thermal and solvent annealing to control the pore size of mesoporous carbon thin films from poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA) block copolymers. They have synthesized PAN-b-PMMA using a metal-free polymerization method and spin-coated the block copolymer into thin films. The block copolymer thin films can self-assemble into various morphologies via thermal or solvent annealing. After pyrolysis, the block copolymer thin films form mesoporous carbon thin films with tunable pore sizes depending on the thermal and solvent annealing conditions. In this rationally designed block copolymer, PAN serves as a carbon precursor and can be directly carbonized into mesoporous carbon, PMMA behaves as a sacrificial phase and can be removed easily to create pores. This work demonstrates that through thermal annealing the temperature can easily tune the pore size and center-to-center spacing of mesoporous carbon thin films. In addition, the choice of solvent in solvent annealing strongly influenced PAN-b-PMMA nanostructures and the pore size of mesoporous carbon thin films. The work provides two simple strategies to control the pore size of mesoporous carbon thin films instead of synthesizing a series of block copolymers of various molecular weights and compositions.

8 ITEMS PINNED

Nickel incorporated carbon nanotube/nanofiber composites as counter electrodes for dye-sensitized solar cells.

Abstract: A nickel incorporated carbon nanotube/nanofiber composite (Ni-CNT-CNF) was used as a low cost alternative to Pt as counter electrode (CE) for dye-sensitized solar cells (DSCs). Measurements based on energy dispersive X-rays spectroscopy (EDX) showed that the majority of the composite CE was carbon at 88.49 wt%, while the amount of Ni nanoparticles was about 11.51 wt%. Measurements based on electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance (R(ct)) of the Ni-CNT-CNF composite electrode was 0.71 Ω cm(2), much lower than that of the Pt electrode (1.81 Ω cm(2)). Such a low value of R(ct) indicated that the Ni-CNT-CNF composite carried a higher catalytic activity than the traditional Pt CE. By mixing with CNTs and Ni nanoparticles, series resistance (R(s)) of the Ni-CNT-CNF electrode was measured as 5.96 Ω cm(2), which was close to the R(s) of 5.77 Ω cm(2) of the Pt electrode, despite the significant difference in their thicknesses: ∼22 μm for Ni-CNT-CNF composite, while ∼40 nm for Pt film. This indicated that use of a thick layer (tens of microns) of Ni-CNT-CNF counter electrode does not add a significant amount of resistance to the total series resistance (R(s-tot)) in DSCs. The DSCs based on the Ni-CNT-CNF composite CEs yielded an efficiency of 7.96% with a short circuit current density (J(sc)) of 15.83 mA cm(-2), open circuit voltage (V(oc)) of 0.80 V, and fill factor (FF) of 0.63, which was comparable to the device based on Pt, that exhibited an efficiency of 8.32% with J(sc) of 15.01 mA cm(-2), V(oc) of 0.83, and FF of 0.67.

Pub.: 08 Aug '12, Pinned: 30 Jun '17

Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing

Abstract: Herein an approach to controlling the pore size of mesoporous carbon thin films from metal-free polyacrylonitrile-containing block copolymers is described. A high-molecular-weight poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA) is synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The authors systematically investigate the self-assembly behavior of PAN-b-PMMA thin films during thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as-spin-coated PAN-b-PMMA is microphase-separated into uniformly spaced globular nanostructures, and these globular nanostructures evolve into various morphologies after thermal or solvent annealing. Surprisingly, through thermal annealing and subsequent pyrolysis of PAN-b-PMMA into mesoporous carbon thin films, the pore size and center-to-center spacing increase significantly with thermal annealing temperature, different from most block copolymers. In addition, the choice of solvent in solvent annealing strongly influences the block copolymer nanostructure and the pore size of mesoporous carbon thin films. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon thin films by tuning thermal or solvent annealing conditions, instead of synthesizing a series of block copolymers of various molecular weights and compositions.

Pub.: 02 Feb '17, Pinned: 29 Jun '17