Structure and magnetic properties of an amine-templated one-dimensional cobalt-fluoro-sulfate containing Co 4 F 4 cubane and hydrogen evolution reaction (HER) performance of its derived carbon-wrapped CoSe 2 nanorods.

Amine-templated 1D cobalt fluoro sulfate of the composition [(CH 3 ) 2 NH 2 ] 2 [Co 4 F 4 (SO 4 ) 3 (C 3 N 2 H 4 ) 4 ], consisting of Co 4 F 4 cubane-type secondary building unit, has been synthesized under solvothermal condition. The magnetic properties of the Co 4 F 4 cubane chain exhibited a low-temperature magnetic ordering below 17 K ( T c ) attributed to intra-cluster ferromagnetic coupling and did not show spin-glass freezing. The selenylation of the Co 4 F 4 cubane chain leads to the formation of sphere-like CoSe 2 in the hydrothermal route (CoSe 2 @HT). At the same time, nanorods of CoSe 2 encapsulated with carbon matrix were obtained in a sealed tube method (CoSe 2 @ST). Moreover, CoSe 2 @ST exhibited a higher hydrogen evolution reaction (HER) activity than CoSe 2 @HT in an acidic medium with 177 mV overpotential to achieve the benchmark current density of 10 mA cm -2 . The promising HER performance of derived CoSe 2 @ST could be attributed to an increase in the geometrical and specific activity due to the encapsulation of N-doped carbon matrix over the CoSe 2 nanorods that facilitate faster charge transfer at the electrode-electrolyte interface and higher electrochemical conductivity than the derived CoSe 2 @HT. This work demonstrates a low-temperature, solvent- and reducing agent-free new synthetic approach for synthesizing framework-derived materials.