Page 419 - Polymer-based Nanocomposites for Energy and Environmental Applications

376 Polymer-based Nanocomposites for Energy and Environmental Applications

Fig. 13.10 SEM images of the nine kinds of the carbon materials (mesoporous carbon (Com),
activated carbon (Ca), carbon black (Cb), conductive carbon (Cc), carbon dye (Cd), carbon fiber
(Cf ), carbon nanotube (Cn), discarded toner from a printer (Cp), and fullerene (C60)).
Reproduced with permission from Wu M, Lin X, Wang T, Qiu J, Ma T. Low-cost dye-sensitized
solar cell based on nine kinds of carbon counter electrodes. Energy Environ Sci
2011;4:2308–15.

structures, and TiO 2 in different amounts were coated onto FTO-glass using an air-
brush system. The thickness of the obtained layer was set by spraying time, and all
samples were sintered at 400°CinN 2 atmosphere. While all carbon structures show
catalytic activity, Com and Cd electrodes exhibited the most efficient activity in
reduction of triiodide. The highest PCE (7.5%) was obtained from the DSC containing
Com- and Pt-based CEs, while the lowest PCE (2.8%) was obtained from the DSC
containing C 60 -based CE. This was attributed to high series resistance and the low
electric conductivity of C 60 layer.
The main problem of carbon-based CE is that low R ct can be achieved only for thick
(10–20 μm) carbon layer that undergo heat treatments at temperatures higher than
400°C and contain conductive additives. Thicker film provides higher surface area
for catalytic reaction, while adding conductive additives and annealing at high tem-
perature allow higher conductivity and better bonding between the carbon particles.
However, the flaking effect after bending the thick carbon layer and the low-
temperature requirement due to flexible substrates appear as problems, and carbon
gel catalyst was one of the solutions proposed. Miettunen et al. [18] have reported