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

Abstract

Pt-free counter electrode (CE) composed of La2MoO6 (La2O3-MoO3) was successfully synthesized by simple pyrolysis of lanthanum acetate (C6H9O6La·xH2O) and hexaammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24·4H2O). Furthermore, three proportions composites catalysts of La2MoO6@MWCNTs based on La2MoO6 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 La2MoO6@MWCNTs composites were determined by scanning electron microscopy, transmission electron microscope and X-ray diffraction. The electrochemical performance of La2MoO6@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 La2MoO6:MWCNTs with the mass ratios of 5:1, 3:1 and 1:1 towards the reduction of I3– to I– under the same conditions, respectively, which are superior to those of MWCNTs (3.94%) and La2MoO6 (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.