Construction of Pt-free electrocatalysts based on hierarchical CoS2/N-doped C@Co-WS2 yolk-shell nano-polyhedrons for dye-sensitized solar cells

摘要： Nanomaterials with yolk-shell structures are identified as promising advanced catalysts in energy conversion devices due to their larger surface area, more efficient active sites, and shorter charge transfer paths. In this work, we developed a facile template method to synthesize yolk-shell structured CoS2/N-doped C@Co-WS2 (CoS2/NC@Co-WS2) as counter electrode material in dye-sensitized solar cells. In detail, zeolitic imidazolate framework-67 (ZIF-67) as a template reacted with (NH4)2WS4 through an anion conversion/exchange processes, which was followed by the subsequent sulfuration reaction. Additionally, the influence of mass ratio between reactions on the morphologies and electrochemical properties of catalysts were further explored. When the mass ratio of the ZIF-67 precursors and (NH4)2WS4 is 5/1, CoS2/NC@Co-WS2 delivered a superior power conversion efficiency of 9.21% for Pt-free dye-sensitized solar cells which was much higher than that of Pt (8.18%). This result could be attributed to the coordination of multiple elements, prominent yolk-shell structure, and the largest surface area (110 m2 g?1).