Synthesis and performance of La2O3@MWCNT composite materials as Pt-free counter electrodes for dye-sensitized solar cells

Pt-free composite counter electrode (CE) composed of La 2 O 3 was successfully synthesized by a simple pyrolysis of Lanthanum acetate hydrate (La(CH 3 COO) 3 ·xH 2 O) in a high-temperature solid phase. Furthermore, three proportion composite catalysts of La 2 O 3 @MWCNTs based on La 2 O 3 and multiwall carbon nanotubes (MWCNTs) were prepared and characterized as Pt-free catalysts for CE in dye-sensitized solar cells (DSSCs). The morphology and structure of La 2 O 3 @MWCNT composites were determined by scanning electron microscopy and X-ray diffraction. The electrochemical performance of La 2 O 3 @MWCNT composite catalysts for CEs was determined by photocurrent-voltage measurements, cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization. The experimental results showed that the power conversion efficiencies of 5.20, 5.12, and 4.70% were obtained for La 2 O 3 : MWCNTs with mass ratios of 5:1, 3:1, and 1:1 as counter electrode towards the reduction of I 3 − /I − ions respectively in the encapsulation of DSSC batteries, which were higher than that of MWCNTs (3.94%) and La 2 O 3 (0.77%) electrode under the similar conditions. The enhanced electrode performance was attributed to relatively larger surface area and higher conductivity of La 2 O 3 @MWCNT composite catalysts.