The catalytic activity of single-wall carbon nanohorns (SWNH) as counter electrodes (CE) of dye-sensitized solar cells (DSC) was studied for the iodide/triiodide redox reaction. The catalytic activities of SWNH and high surface SWNH (HS-SWNH) obtained by partial oxidation of SWNH were assessed based on charge-transfer resistances (Rct) and current–voltage curves. A half-cell configuration was used, and CE performances were compared to CEs made of carbon black (CB) and Pt. A CE assembled with HS-SWNH and mixed with 10 wt.% of hydroxyethyl cellulose (HEC) - HS-SWNH/HEC was found to have the highest electrocatalytic activity (lowest Rct) among all the carbon-based CEs tested when annealed at 180 °C (Rct = 141 Ω cm2); however, a very thick film (several tens of µm) would be required in order to perform comparably to a Pt CE. The annealing of such CE at higher temperatures (above 400 °C) did not improve its catalytic activity, contrary to the other studied carbonaceous CEs.
The redox catalytic activity of SWNH and HS-SWNH decorated with Pt was also studied on a half-cell configuration and compared to that of Pt/CB and pristine Pt. The Pt/SWNH/HEC CE showed the highest electrocatalytic activity per mass of Pt, needing just 50% of Pt load to yield the same electrocatalytic activity of a DSC equipped with a Pt CE, but having half of its transparency. Additionally, applications in temperature-sensitive substrates are envisioned for the Pt/SWNH/HEC CE due to the use of lower annealing temperatures. Copyright © 2012 John Wiley & Sons, Ltd.