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

Abstract

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.