Perovskite-Like Metal-Organic Framework of Cobalt Formate as High-Performance Electrocatalyst for Dye-Sensitized Solar Cells: From Microcube to Nanotube

Perovskite-like metal-organic framework of cobalt formate, that is, [(CH₃)₂NH₂][Co(HCOO)₃]_n (denoted as Co(HCOO)₃), has successfully grown on a conductive carbon cloth (CC) with or without surfactant. The insertion of various thiolate surfactants, for example, 2-mercaptobenzoxazole (MBO), 2-mercaptobenzimidazole (MBI), and 2-mercaptobenzothiazole (MBT), effectively confined the particle size to microcubes owing to the core@shell structure of H₂O@dimethylformamide (DMF) reverse micelles. The insertion of benzeneselenolate (PhSe⁻) caused the formation of both microcubes and nanotubes. When some H₂O@DMF reverse micelles were intensively surrounded by benzeneselenious anions (R-SeO₃⁻ or R-SeO₂⁻), the strong π–π stacking among benzenes would induce the crystal growth through 1D direction, leading to the formation of Co(HCOO)₃ nanotubes uniformly covered on CC. Among all the CC/Co(HCOO)₃ electrodes, the CC/PhSe-doped Co(HCOO)₃ electrodes reached the optimal electrocatalytic performance toward triiodide reduction, and thereby functioned as the outstanding counter electrode in dye-sensitized solar cell (DSSC). Good DSSCs’ efficiencies of 9.73% (1 sun) and 24% (at 6 klux) can be obtained by using CC/PhSe-doped Co(HCOO)₃, which surpassed the cells with CC/bare Co(HCOO)₃ (5.25% at 1 sun) and the benchmark CC/Pt (9.85% at 1 sun), owing to numerous electro-donating R-SeO₃⁻/R-SeO₂⁻ dopants as active sites and facile 1D charge-transfer pathways.