A Reusable N-Doped-Carbon-Coated Mo₂ C Composite Counter Electrode for High-Efficiency Dye-Sensitized Solar Cells

The design and development of efficient and stable nonprecious-metal-based catalysts for counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) has received a great deal of attention. In this work, molybdenum carbide nanoparticles homogeneously distributed in a nitrogen-rich carbon matrix (Mo₂ C@NC) have been synthesized from inexpensive raw materials (polyoxometalate and dicyandiamide) by a facile one-step solid-phase synthesis method. The novel Mo₂ C@NC hybrid was not only used as a CE in a DSSC, but also showed superior catalytic activity towards I₃^- /I^- as a redox electrolyte. The power conversion efficiency of a DSSC with Mo₂ C@NC as the CE was as high as 6.49 %, comparable to that with Pt (6.38 %). The CE was prepared by a drop-coating method, without the addition of another conductive polymer. Most importantly, the method circumvents the problem of the sample falling off from the fluorine-doped tin oxide (FTO), and the CE could be repeatedly reused with unchanged efficiency. Therefore, it opens the way for the development of platinum-free catalysts with low cost, simple processing, good stability, and high efficiency.