Morphology Effect of NiSe Hierarchical Microspheres on the Performance of Dye-Sensitized Solar Cells

Three-dimensional (3D) hierarchical micro/nanostructures possess excellent catalytic properties for I-3(-) reduction because of the more catalytic active sites exposed at the surface of 3D microstructure and fast electron transfer along the ID nanostructure. Herein, 3D hierarchical NiSe microspheres assembled with nanorods (NiSe-3HM) have been controllable synthesized when R-1 (n(DETA) = 0.4 mol and n(N2H4 center dot H2O) = 0.5 mol). The 3D compact microspheres (NiSe-C) and 3D hollow microspheres (NiSe-H) assembled with nanoparticles are prepared when R-2 (n(DETA) = 0.1 mol and n(N2H4 center dot H2O) = 0.4 mol), and R-3 (n(DETA) = 0.2 mol, and n(N2H4 center dot H2O) = 0.2 mol), respectively. The possible formation mechanisms of 3D NiSe microspheres with different morphologies are proposed. The hydrolyzed Ni2+ will be coordinated with diethylenetriamine (DETA) to form chelate complex ([Ni(DETA)(2)](2+)). Meanwhile, SeO32- is reduced by N2H4 center dot H2O to produce highly reactive Se and then further converted to Se2- through a disproportionation process. Then newly formed ([Ni(DETA)(2)](2+)) will be reacted with Se2- to produce NiSe microspheres with different morphologies, which can be controllable prepared by tuning amount of substance of DETA and N2H4 center dot H2O. The obtained NiSe-3HM, NiSe-C, and NiSe-H are used as counter electrode (CE) materials in dye-sensitized solar cells (DSSCs) for testing the catalytic property. DSSCs based on the NiSe-3HM electrode achieve PCE of 7.76%, which is obviously higher than those of NiSe-H and NiSe-C and comparable to that of Pt (8.0%). The CV curves, EIS spectra, and Tafel plots indicate that NiSe-3HM possessed the superior catalytic activity and electrochemical stability for the reduction of I-3(-). It can be attributed to the unique 3D micro/nanostructures assembled with the nanorods, which provided fast electron transfer along the nanorods and more active sites exposed for the reduction of I-3(-).