Controllable Construction Of Highly Catalytic Activity Nickel(Cobalt) Chalcogenide And Its Performance As A Counter Electrode

Dye-sensitized solar cells(DSSCs)received much attention owing to their low cost and high photoelectric conversion efficiency.As an important component of DSSCs,the counter electrode plays an role in collecting electrons from the external circuit and catalyzing triiodide(I3-)reduce to iodide(I-).The conventional counter electrode catalyst is noble metal Pt,but the cost of the Pt-based DSSCs was expensive,so it is necessary to develop the Pt-free counter electrode catalysts with low-cost and better electrochemical properties(electrocatalytic activity,conductivity,and electrochemical stability),which is important for the future development and application of the DSSCs.In this paper,controllable construction of highly catalytic activity nickel(cobalt)chalcogenide and their electrochemical properties of them as DSSCs counter electorde materials were investigated.The main research contents are as follows:The 3D hierarchical structure of NiSe microspheres assembled with one-dimensional nanorods(NiSe-3HM),3D compact NiSe microspheres assembled with nanoparticles(NiSe-C),and 3D hollow NiSe microspheres assembled with particles(NiSe-H)were controllable prepared by tailoring the amount of substance of diethyltriamine and hydrazine hydrate in the reaction system.A photoelectric conversion efficiency comparable to that of the Pt-based DSSCs was achieved when DSSCs fabricated with these NiSe microspheres with three-dimensional micro-nanostructure.A controllable-synthesis strategy for preparing monodisperse NiSe2 nanorods(NiSe2-R)and small-sized NiSe2 nanoparticles(NiSe2-P)was developed.The small sized NiSe2 nanocrystals can expose a high proportion of surface atoms,which facilitates the catalytic reduction of I3-.A series of electrochemical results indicated that the elaborated NiSe2-R and NiSe2-P possessed excellent electrocatalytic activity and photoelectric conversion performance.The active-site-enriched CoSe2/nitrogen-doped carbon(CoSe2/NC)composite exhibited better electrocatalytic activity and photoelectric conversion properties than that of the Pt.The newly introduced nitrogen-doped species(graphite-N and pyridinium-N)and CoSe2 acted as the active sites for catalyzing I3-to I-,while the charge-transfer capability was further enhanced by nitrogen doping,then the activity of the CoSe2/NC composite was synergistically improved.The small-sized NiS nanoparticles partially embedded in the surface of CNTs by the the hot-injection method,which endows NiS/CNTs composites possessed abundant distributed NiS/CNTs interfaces.The NiS/CNTs composite with unique interface structure exhibited superior electrocatalytic activity and fast electron transport capability.DSSCs fabricated with NiS/CNTs composite reached a photoelectric conversion efficiency of up to 10.82%,superior to that of the Pt reference device(8.02%).The theoretical calculation and work function results revealed that the NiS/CNTs interface was not only the electron fast conduction center,but also the catalytic active center of I3-to I-.