Pyrolysis synthesis of CuWO4@C composite catalysts as Pt-free counter electrode for dye-sensitized solar cells

Transition metal compound catalysts have potential applications in Pt-free counter electrode (CE), which are one of the important strategies for reducing costs and improving power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, CuWO4@C composite catalysts were synthesized by pyrolyzing Cu-based polyoxotungstate (H3PW12O40) precursor in presence of polyaniline. The effect of pyrolysis temperature (600, 700, 800, 900, 1000 and 1100 ℃) on the compositions, morphologies and structures of CuWO4@C composite was investigated by Thermogravimetry-Derivative thermogravimetry-Differential scanning calorimetry (TG-DTG-DSC) simultaneous, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and N2 adsorption-desorption analysis. The photovoltaic properties of different CuWO4@C composites CEs were determined by photocurrent-photovoltage (J-V) measurement. The results reveal that the pyrolysis at 800 ℃ was optimum to get the best CuWO4@C composite CE, which yielded the highest PCE of 7.11% for the regeneration of I3−/I− couple in the DSSCs. The structure-activity relationship of the CuWO4@C composite catalysts was discussed.