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 CoSe 2 /N-doped carbon (CoSe 2 /NC) and CoS 2 /N-doped carbon (CoS 2 /NC) hybrids with small-size pores were successfully prepared through direct selenization and sulfurization of ZIF-67, respectively. DSSCs fabricated with CoSe 2 /NC (CoS 2 /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 CoSe 2 (CoS 2 ) and N-doped carbon. As for this hybrid, CoSe 2 (CoS 2 ) 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 CoSe 2 (CoS 2 ). Therefore, low-cost CoSe 2 /NC hybrid has great potential for replacing noble Pt for the reduction of I 3 – in DSSCs.