Low-cost electrospun WC/C composite nanofiber as a powerful platinum-free counter electrode for dye sensitized solar cell

Tungsten carbide/carbon (WC/C) composite nanofibers were successfully prepared through electro-spinning followed by a one-step heat treatment using in-situ carburization. The WC/C nanofibers were applied to low-cost and platinum-free counter electrodes for dye sensitized solar cells (DSSCs), and their catalytic activities were investigated and compared to platinum (Pt) CEs for triiodide/iodide (I-3(-)/I-) as well as organic disulfide/thiolate (T-2/T-) electrolytes. When WC/C nanofibers are used as the CE catalyst in iodine electrolytes, the DSSCs exhibited a power conversion efficiency (PCE) of 7.77%, corresponding to 96% of that of Pt CEs. In the case of T-2/T- redox couples, the DSSCs based on WC/C nanofibers achieved PCE of 5.85%, which is almost twice that of Pt (3.07%). The high catalytic activities of WC/C nanofibers are attributed to synergetic effects from the combination of catalytically active WC and one-dimensional (1D) conductive carbon acting as an efficient charge transport pathway. In addition, spray-coated WC/C nanofiber CE films have a three-dimensional porous network, enhancing the permeation of the electrolyte into the CE film and the diffusion of redox couples. The electrospinning process used for the synthesis of the WC/C nanofibers is facile and scalable and is therefore promising for the commercialization of DSSCs. (C) 2014 Elsevier Ltd. All rights reserved.