VC@C composites derived from polyoxovanadate assisted by dicyandiamide as low-cost platinum-free counter electrode electrocatalyst for dye-sensitized solar cells

Vanadium-based carbides have been applied as Pt-free counter electrodes (CEs) electro-catalysts for dye-sensitized solar cells (DSSCs) due to the advantages of earth-abundant reserves, diverse composition , ease modification, and low cost. Herein, the polyoxovanadate (NH 4 ) 2 V 6 O 16 as V source assisted by dicyandiamide (C 2 H 4 N 4 ) as C source via simply physical mixing by ball-milling to assemble VC@C precursors. And then, five different VC@C composites derived from precursors with mass ratios of dicyandiamide to polyoxovanadate of 5:1, 10:1, 15:1, 20:1 and 25:1 at 900 °C, and further achieved power conversion efficiencies (PCEs) of 5.4%, 5.6%, 6.6%, 6.2% and 5.1% as CEs for regenerate traditional I 3 − /I − couple in the encapsulated DSSCs, respectively. The effects of different mass ratio of dicyandiamide on the catalytic performances of VC@C composite CEs were also assessed using cyclic voltammetry , electrochemical impedance spectroscopy and Tafel polarization experiments. The photocurrent-photovoltage ( J - V ) results indicated that VC@C composites CEs had high conductivity and rich number of active sites, which indicated that VC@C composites could be a cost-effective and high-performance alternative Pt-based CEs catalyst for DSSCs.