Structure and magnetic properties of an amine-templated one-dimensional cobalt-fluoro-sulfate containing Co4F4 cubane and hydrogen evolution reaction (HER) performance of its derived carbon-wrapped CoSe2 nanorods.

Abstract

Amine-templated 1D cobalt fluoro sulfate of the composition [(CH3)2NH2]2[Co4F4(SO4)3(C3N2H4)4], consisting of Co4F4 cubane-type secondary building unit, has been synthesized under solvothermal condition. The magnetic properties of the Co4F4 cubane chain exhibited a low-temperature magnetic ordering below 17 K (Tc) attributed to intra-cluster ferromagnetic coupling and did not show spin-glass freezing. The selenylation of the Co4F4 cubane chain leads to the formation of sphere-like CoSe2 in the hydrothermal route (CoSe2@HT). At the same time, nanorods of CoSe2 encapsulated with carbon matrix were obtained in a sealed tube method (CoSe2@ST). Moreover, CoSe2@ST exhibited a higher hydrogen evolution reaction (HER) activity than CoSe2@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 CoSe2@ST could be attributed to an increase in the geometrical and specific activity due to the encapsulation of N-doped carbon matrix over the CoSe2 nanorods that facilitate faster charge transfer at the electrode-electrolyte interface and higher electrochemical conductivity than the derived CoSe2@HT. This work demonstrates a low-temperature, solvent- and reducing agent-free new synthetic approach for synthesizing framework-derived materials.