Nanocomposite Graphene/Pt Electrocatalyst as Economical Counter Electrode for Dye‐Sensitized Solar Cells

Abstract

AbstractPlatinum is the most common electrocatalyst used as a counter electrode (CE) in dye‐sensitized solar cells (DSSCs). However, due to its high cost, Pt presents an obstacle to popularizing DSSCs in energy‐harvesting applications. Therefore, effective utilization of Pt and good understanding of the role of its composites are critical issues for developing low‐cost DSSCs with high efficiency. In this study, a graphene/Pt nanoparticles (GN/PtNPs) nanocomposite is synthesized as the catalyst for the CE of a DSSC. GN/PtNPs catalysts with various of PtNP loadings (10–60 wt %) are obtained by using a polyol reduction method, and are subsequently characterized by using X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. A solar‐to‐electricity conversion efficiency (η) of 8.79 % is achieved for a DSSC with a GN/PtNPs CE containing 20 wt% PtNPs (GN/PtNPs‐20 %); this η value is higher than those of the cells with CEs consisting of pristine GN (7.65 %) or sputtered Pt (s‐Pt, 8.58 %). Electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization plots reveal that the higher η value of the cell with GN/PtNPs‐20 % is due to the higher electrocatalytic ability of the CE for the reduction of triiodide ions (I3−) and the reduced charge‐transfer resistance at the CE/electrolyte interface. The excellent electrocatalytic performance of GN/PtNPs‐20 % is attributed essentially to its high intrinsic heterogeneous rate constant for the I3− reduction reaction and partly to its high electrochemical surface area, which are quantitatively calculated by means of a rotating disk electrode system and the Koutecký–Levich equation.