Platinum 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.
The electrochemical detection of hydrogen peroxide (H2O2) has attracted much attention recently. Meanwhile, the size of nanoparticles which significantly influences electrocatalytic activity is crucial for electrocatalysts. Hence, we prepared five different size-selected Pt/graphene-modified glassy carbon (GC) electrodes to characterize H2O2level via electrochemical measurements. During the preparation of the nanocomposites, size-selected Pt nanoparticles (NPs) with the mean diameter of 1.3, 1.7, 2.9, and 4.3 nm were assembled onto the graphene surfaces. The electrochemical measurement results are size-dependent for Pt NPs when sensing H2O2. When all cyclic voltammogram results from various electrodes are compared, the Pt-1.7 nm/G-modified GC electrode has the highest reduction current, the best detection limit, and the best sensitivity.
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