CoSe2/N-Doped Carbon Hybrid Derived from ZIF-67 as High-Efficiency Counter Electrode for Dye-Sensitized Solar Cells

To achieve a satisfactory photovoltaic performance in dye-sensitized solar cells (DSSCs), counter electrode (CE) catalysts with low cost, superior catalytic activity, and excellent conductivity should be developed. In this work, the unique rhombic dodecahedron morphology of CoSe2/N-doped carbon (CoSe2/NC) and CoS2/N-doped carbon (CoS2/NC) hybrids with small-size pores were successfully prepared through direct selenization and sulfurization of ZIF-67, respectively. DSSCs fabricated with CoSe2/NC (CoS2/NC) electrode achieved a photoelectric conversion efficiency of 9.06% (8.74%), superior to that of Pt-based DSSCs (8.03%). The satisfactory performance was mainly attributed to the synergic effect between CoSe2 (CoS2) and N-doped carbon. As for this hybrid, CoSe2 (CoS2) and the N-doped species (graphitic-N and pyridinic-N) of carbon framework as catalytic active centers supplied abundant active sites toward I-3(-) reduction, while NC as fast conductivity platforms facilitated the charge transfer. Meanwhile, the unique rhombic dodecahedron morphology with small-size pores of the hybrids could also accelerate the permeation of redox electrolyte, thus promoting the catalytic reaction between redox species (I-/I-3(-)) and inner active sites of CoSe2 (CoS2). Therefore, low-cost CoSe2/NC hybrid has great potential for replacing noble Pt for the reduction of I-3(-) in DSSCs.