AuNP/graphene nanohybrid prepared by dry plasma reduction as a low-cost counter electrode material for dye-sensitized solar cells

Au nanoparticles (NPs) with a radius ranging from 4 ∼ 18 nm (mostly 11 nm) were stably and uniformly hybridized on the surface of reduced graphene oxide (RGO) after co-reduction of Au precursor ions and graphene oxide (GO), to Au atoms and RGO, respectively. The hybridization was provided by dry plasma reduction (DPR) operated under atmospheric pressure and at a low temperature without any toxic chemicals. The structure of the AuNP/RGO nanohybrid was characterized by SEM, TEM, XPS, XRD and Raman spectroscopy. Raman spectra indicated that DPR induced an increase in the degree of clustering of the sp2 phase in addition to sp2 bond restoration. Increasing the number of AuNP/RGO layers yielded a decrease in the transmittance and sheet resistance of the AuNP/RGO nanohybrid. A developed electrode based on the AuNP/RGO nanohybrid showed high electrochemical catalytic activity and high conductivity in comparison with the AuNP and GO electrodes. Thus, the AuNP/RGO nanohybrid fabricated by DPR could be an excellent material for a low-cost counter electrode for dye-sensitized solar cells using Co2+/Co3+ redox electrolyte.