Abstract
NiCu bimetallic nanoparticle-decorated graphene was prepared by hydrothermal treatment to be utilized as an efficient and alternative Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). The results indicated that the performance of the introduced modified graphene as CE strongly depends on the composition of the metallic nanoparticles. Typically, Ni-, Ni0.25Cu0.75-, Ni0.6Cu0.4- and Ni0.75Cu0.25-decorated graphene were synthesized. Investigation of the electrochemical characteristics indicated that the graphene decorated by Ni0.75Cu0.25 nanoparticles shows the highest catalytic activity and conductivity compared to the other prepared formulations as well as pristine graphene. In DSSC, Ni0.75Cu0.25 nanoparticle-decorated graphene can remarkably improve the catalytic activity toward triiodide reduction and lower the resistance at the electrolyte CE interface. Accordingly, the obtained energy conversion efficiencies were 1.72%, 2.39%, 1.24%, 2.87% and 5.1% for pristine, Ni-, Ni0.25Cu0.75-, Ni0.6Cu0.4- and Ni0.75Cu0.25-decorated graphene, respectively. The obtained efficiency for Ni0.75Cu0.25-decorated graphene is comparable with Pt-based DSSC fabricated by the same procedure (5.9%) which recommends exploiting the introduced modified graphene as efficient and cost-effective CE for the large-scale fabrication of photovoltaic devices. The catalytic performance of the best formulation was examined toward methanol electrooxidation; the results indicated effective and stable electrocatalytic activity. (C) 2015 Elsevier B.V. All rights reserved.