A CNT/TiO_2-x N_x composite as a high electrocatalytic active counter electrode for a dye-sensitized solar cell

A CNT/TiO_2-x N_x composite was synthesized by an integrated hydrothermal and NH₃ annealing method. The as-synthesized composite was characterized by XRD, SEM, TEM and XPS, and its catalytic activity as a counter electrode for a dye-sensitized solar cell (DSSC) was investigated by cyclic voltammetry, Tafel-polarization, electrochemical impedance spectroscopy and I-V techniques. Results show that nitrogen was successfully doped into the TiO₂ crystal lattice. CNTs with a diameter of 30-50 nm interconnect with the TiO_2-x N_x nanowires with a diameter of 3-8 nm, leading to a network structure. Benefiting from the high electrocatalytic activity of TiO_2-x N_x and the high conductivity of CNTs, the composite demonstrates a higher power conversion efficiency (7.16%) than pure CNTs (4.67%) as the counter electrode of the DSSC, and this value is comparable to that of a noble Pt electrode.