NiO nanoparticles deposited on graphene platelets as a cost-effective counter electrode in a dye sensitized solar cell

NiO nanoparticles were deposited homogeneously over few layered graphene platelets (GPs) by pulsed laser ablation. The material was used as an electrocatalyst for the counter electrode (CE) of a dye-sensitized solar cell. GPs were synthesized by oxidation of graphite powder followed by a thermal exfoliation and reduction process. The CE made from GPs with NiO nanoparticles attached (NiO-GP) yielded 3.06% power conversion efficiency which is comparable to a conventional platinum thin film based CE (3.57%). The fill factor and short circuit current density were 0.61 and 7.53 mA/cm2, respectively. The NiO-GP CE outperformed CEs produced using both unsupported NiO nanoparticles (2.03%) and pristine GPs (2.46%). Catalytic activities of the CEs were analyzed using electrochemical impedance spectroscopy. Charge transfer resistances for the two interfaces GP-electrolyte and NiO-electrolyte of the NiO-GP CE were 0.85 and 1.72 Ω cm2, respectively. These values were much smaller than that of the bare GP (3.96 Ω cm2) and NiO nanoparticle (20.85 Ω cm2) based CEs. Thus the catalytic ability of each component in the NiO-GP mixture is better than those of the individual components, indicating a synergistic effect. The resistance for the Pt-electrolyte interface (0.63 Ω cm2) was only slightly better than that for NiO-GP.