Morphology-dependent catalysis on nanostructures Fe2O3@MWCNT as Pt-free counter electrode for dye-sensitized solar cells

Abstract

The doped transition metal oxides (TMOs) substitute for the traditional Pt as the counter electrode (CE) catalyst is a unique way to reduce the cost and improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, four different morphologies and size of Fe2O3 (nanodiscus (ND), nanocubes (NC), nanorings (NR), nanoball (NB)) assisted by multi-walled carbon nanotube (MWCNT) to prepare Fe2O3@MWCNT composites, and then were further utilized in the encapsulated DSSCs. The obtained different morphologies Fe2O3@MWCNT composites had been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption-desorption. The significant effects of different morphologies of Fe2O3 on the electrochemical activity of Fe2O3@MWCNT composites as CEs were confirmed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization experiments. The DSSCs using Fe2O3@MWCNT composites CEs achieved high PCEs of 6.34 (ND), 6.53(NC), 6.65(NR), and 7.09% (NB) to regenerate traditional I3−/I− shuttles by the photocurrent-photovoltage (J-V) test, respectively, which is due to the synergistic effect between Fe2O3 and MWCNT to improve electrical conductivity and promote a high number of active catalytic sites, implying a remarkable alternative of Pt-free catalyst that can be applied to the encapsulated DSSCs as CEs.