NiCu bimetallic nanoparticle-decorated graphene as novel and cost-effective counter electrode for dye-sensitized solar cells and electrocatalyst for methanol oxidation

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-, Ni_0.25Cu_0.75-, Ni_0.6Cu_0.4- and Ni_0.75Cu_0.25-decorated graphene were synthesized. Investigation of the electrochemical characteristics indicated that the graphene decorated by Ni_0.75Cu_0.25 nanoparticles shows the highest catalytic activity and conductivity compared to the other prepared formulations as well as pristine graphene. In DSSC, Ni_0.75Cu_0.25 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-, Ni_0.25Cu_0.75-, Ni_0.6Cu_0.4- and Ni_0.75Cu_0.25-decorated graphene, respectively. The obtained efficiency for Ni_0.75Cu_0.25-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.