Hierarchical Ni-MoSe_x@CoSe₂ core-shell nanosphere as highly active bifunctional catalyst for efficient dye-sensitized solar cell and alkaline hydrogen evolution

Core-shell structured nanocomposites based on transition metal selenides have a broad development prospect as Pt-free electrocatalyst in energy conversion due to large surface area, rich edge sites, as well as synergistic interactions between the core and shell. Herein, the preparation of core-shell structured transition metal selenides nanospheres was achieved through a facile wrapping process using zeolitic imidazolate framework (ZIF-67) as the cobalt source, which assembled on glycerol precursor nanospheres. After a selenization treatment, this formed core-shell structure had a Ni-MoSe_x inner core, supporting the CoSe₂ outer shell (denoted as Ni-MoSe_x@CoSe₂ CSNs). And the resultant Ni-MoSe_x@CoSe₂ CSNs not only had a large number of active sites, but also was good for adsorbing/transferring iodine and hydrogen ions. Therefore, Ni-MoSe_x@CoSe₂ delivered superior performance in dye-sensitized solar cells (DSSCs) and alkaline hydrogen evolution reactions (HERs). DSSCs based on Ni-MoSe_x@CoSe₂ CSNs performed an outstanding power conversion efficiency (PCE) of 9.58% which was much higher than that of Pt (8.32%). A lower onset potential of 37.5 mV and a smaller Tafel slope of 68.9 mV dec⁻¹ were achieved by Ni-MoSe_x@CoSe₂ as electrocatalysts for HER in 1.0 M KOH. This work affords a new idea for the design of cut-price core-shell nanomaterials with high efficiency and can be extended to the synthesis of other electrocatalysts substituting Pt-based catalysts.