Mesoporous Ni0.85Se Nanospheres Grown in Situ on Graphene with High Performance in Dye-Sensitized Solar Cells.

Mesoporous Ni0.85Se nanospheres grown on graphene were synthesized via the hydrothermal approach. Because of the exceptional electron-transfer pathway of graphene and the excellent catalytic ability of the mesoporous Ni0.85Se nanospheres, the nanocomposites exhibited excellent electrocatalytic property as the counter electrode (CE) of dye-sensitized solar cells. More catalytic active sites, better charge-transfer ability and faster reaction velocity of Ni0.85Se@RGO (RGO = reduced graphene oxide) CE led to faster and more complete I3(-) reduction than Pt, Ni0.85Se, and RGO CEs. Furthermore, the power conversion efficiency of Ni0.85Se@RGO CE reached 7.82%, which is higher than that of Pt CE (7.54%). Electrochemical impedance spectra, cyclic voltammetry, and Tafel polarization were obtained to demonstrate positive synergetic effect between Ni0.85Se and RGO, as well as the higher catalytic activity and the better charge-transfer ability of Ni0.85Se@RGO compared with Pt CE.