Co–Cu–WSx ball-in-ball nanospheres as high-performance Pt-free bifunctional catalysts in efficient dye-sensitized solar cells and alkaline hydrogen evolution

Abstract

Ball-in-ball hollow nanostructures (BHSs) based on transition metal chalcogenides hold great promise as electrocatalytic materials for fundamental studies. In this work, we have developed a moderate method to realize the synthesis of transition metal sulfide ball-in-ball hollow nanospheres (Co–Cu–WS_x, Co–WS_x and Co–CuS_x BHSs). Importantly, it was found that these ball-in-ball hollow nanospheres exhibited superior electrocatalytic properties for dye-sensitized solar cells (DSSCs) and the hydrogen evolution reaction (HER) in alkaline medium. Compared with the ternary Co–WS_x and Co–CuS_x counterparts, the quaternary Co–Cu–WS_x nanospheres exhibited excellent behavior in accelerating the reduction of I₃⁻ in DSSCs and expediting the HER in water splitting. Specifically, DSSCs based on Co–Cu–WS_x BHSs achieved a splendid power conversion efficiency (PCE) of 9.61% which was higher than that of Pt (8.24%) under the same conditions. Also, a lower η₁₀ of 82.5 mV and a smaller Tafel slope of 53.8 mV per decade were obtained for a Co–Cu–WS_x electrocatalyst for the HER in 1.0 M KOH. The present approach is proposed as a new idea for the design of transition metal sulfide hollow nanospheres for different energy conversion applications.