Synthesis Of Lanthanum Molybdate As A Counter Electrode Catalyst For Triiodide/Iodide Redox Couple In Dye-sensitized Solar Cell

Dye-sensitized solar cells（DSCs） are photovoltaic device which transfers the sun-light to electrical energy. The counter electrode（CE） loads catalyst which is an important material, providing one of vital roles for the iodide redox couple regeneration. Up to now, noble platinum has been widely used as CE materials. However, Pt is the noble metal and limited storage. Moreover, Pt can be corroded in I3-/I- electrolyte, influencing the stability of the DSCs. These shortcomings limit Pt of large-scale application in DSCs, so it is essential to develop Pt-free catalytic materials. Inorganic nonmetallic materials are developing a new type of catalytic materials, and prepared Lanthanum Molybdates were used as a counter electrode catalyst. The prepared Lanthanum Molybdates also were modified in two different methods by multi-walled carbon nanotube（MWCNTs）. The prepared Lanthanum molybdates are explored its crystalline form, its morphology and its application in DSCs. The main contents are as follows:Part 1: La₂Mo₂O₉ was synthesized by a series of different chemical methods. X-ray diffraction（XRD）, Cyclic Voltammetry（CV）, electrochemical impedance spectroscopy（EIS） and Tafel-polarization（Tafel） experiments were characterized with an electrochemical workstation system.Part 2, Lanthanum molybdates with different mole ratio were prepared by conventional solid state reaction method. X-ray diffraction（XRD） and Scanning electron microscopy（SEM） were used to characterize them. Cyclic Voltammetry（CV）, electrochemical impedance spectroscopy（EIS）, Tafel-polarization（Tafel） and J-V curve of a dye-sensitized solar cell（J-V） experiments were characterized with an electrochemical workstation system. 6.5La₂O₃·7MoO₃ is the most advantageous in the 25 prepared Lanthanum molybdates. The DSCs using 6.5La₂O₃·7MoO₃ CE produced power conversion efficiency of 1.71%. Two elements of Lanthanum and molybdenum with different molar fraction play an important role on the catalytic properties.Part 3, to improve the electrical conductivity and the catalytic activity, the prepared Lanthanum Molybdates were physically mixed with multi-walled carbon nanotube, and the prepared Lanthanum Molybdates were sprayed onto the FTO glass which was pre-coated with MWCNTs. MWCNTs-supported La₂O₃·0MoO₃（1 : 5） showed a high power conversion efficiency of 5.20%, and there are 6.75 times as much as La₂O₃·0MoO₃. The ΔEp（peak-peak separation） for La₂O₃·0MoO₃ /MWCNTs was only 146 mV, and its reversibility is the best. And it gave an impressive catalytic activity and the device yielded a high power conversion effciency of 6.34%. After optimization, it has shown that the catalytic activity and power conversion efficiency of three kinds of different Lanthanum Molybdates had a certain degree increase. It can be attributed to the combination of the high catalytic activity and the high electrical conductivity into one composite.