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 I3– 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–/I3–) and inner active sites of CoSe2 (CoS2). Therefore, low-cost CoSe2/NC hybrid has great potential for replacing noble Pt for the reduction of I3– in DSSCs.