Synthesis of La2MoO6@MWCNTs composite catalysts as Pt-free counter electrodes for dye-sensitized solar cell

Pt-free counter electrode (CE) composed of La 2 MoO 6 (La 2 O 3 -MoO 3 ) was successfully synthesized by simple pyrolysis of lanthanum acetate (C 6 H 9 O 6 La· x H 2 O) and hexaammonium heptamolybdate tetrahydrate ((NH 4 ) 6 Mo 7 O 24 ·4H 2 O). Furthermore, three proportions composites catalysts of La 2 MoO 6 @MWCNTs based on La 2 MoO 6 and multiwall carbon nanotubes (MWCNTs) were prepared and characterized as Pt-free catalyst for CE in dye-sensitized solar cells (DSSCs). The morphology and structure of La 2 MoO 6 @MWCNTs composites were determined by scanning electron microscopy, transmission electron microscope and X-ray diffraction. The electrochemical performance of La 2 MoO 6 @MWCNTs composite catalysts for CEs was determined by photocurrent-voltage measurements, cyclic voltammetry , electrochemical impedance spectroscopy , and Tafel polarization. The power conversion efficiencies of 4.68%, 4.87% and 5.06% are obtained for La 2 MoO 6 :MWCNTs with the mass ratios of 5:1, 3:1 and 1:1 towards the reduction of I 3 – to I – under the same conditions, respectively, which are superior to those of MWCNTs (3.94%) and La 2 MoO 6 (1.71%) electrodes. The experimental results reveal that the presence of MWCNTs results in an augmented active catalytic surface area and enhanced charge transfer from CE to the electrolyte.