Dual Sites of CoO Nanoparticles and Co–Nx Embedded within Coal-Based Support toward Advanced Triiodide Reduction

摘要

Herein, coal-based composites embedded with CoO nanoparticles and Co–N_(x ) dual sites are constructed and used for triiodide reduction in a dye-sensitized solar cell. Concentrated hydrochloric acid is first provided to pretreat coal so as to eliminate interference from other metal impurities. The ash-rich coal with addition of cobalt phthalocyanine and pyrolyzed at 800 °C (denoted as Coal-10 wt % CoPc-800) as the counter electrode shows a much enhanced activity for triiodide reduction reaction with the power conversion efficiency of 8.32%, which is better than that of the Coal-800 counter electrode (7.83%), and also exceeds that of the Pt counterpart (8.02%), revealing the generated Co–N_(x ) and CoO nanoparticles sites derived from CoPc can synergistically boost the electrochemical activity. In particular, a significantly enhanced electrochemical performance is achieved after introducing an additional 33 wt % TiO_(2) binder into the above-mentioned Coal-10 wt % CoPc-800 (denoted as Coal-10 wt % CoPc-800-33 wt % TiO_(2)). The binding strength between the obtained counter electrode material and the fluorine doped tin oxide glass substrate is improved and shows the highest power conversion efficiency of 8.82%, the lowest E _(pp) (the energy of peak-to-peak separation) of 0.16 V, and the lowest R _(s) (serial resistance) of 6.3 Ω, which exceeded those of Pt and other coal-based counter electrodes. This work paves a promising facile and viable avenue for the tailoring of coal-derived high-efficient yet cost-effective catalysts for renewable energy conversion and storage technologies.