Metal–organic framework (MOF) derived flower-shaped CoSe2 nanoplates as a superior bifunctional electrocatalyst for both oxygen and hydrogen evolution reactions

The development of a non-precious metal-based stable and cost-effective bifunctional electrocatalyst remains a significant challenge for the production of hydrogen (H2) and oxygen (O2) through water splitting. Although some progress has been made to develop efficient electrocatalysts from transition metal-based nanostructured selenides, the electrocatalyst derived from metal–organic framework (MOF) transition metal selenides demands additional effort due to their well-defined morphological structure and high accessible surface area resulting in better electrochemical performances. Herein, by tuning the selenylation technique through a facile solvothermal approach, we have successfully synthesized flower-like CoSe2 nanoplates termed MOF-D CoSe2, derived from a Co-MOF of the formula [Co3(tiron-bpy)2(bpy)(H2O)8]·(H2O)2 [tiron = 4,5-dihydroxy-1,3-benzenedisulfonate disodium salt, and bpy = 4,4′-bipyridyl]. The MOF-D CoSe2 performs as an excellent bifunctional electrocatalyst, which requires an overpotential of 320 mV to achieve the predefined current density of 10 mA cm−2, with a Tafel slope of 60 mV dec−1 in 1 M KOH to catalyze the oxygen evolution reaction (OER). For the hydrogen evolution reaction (HER), MOF-D CoSe2 needs an overpotential of 195 mV at 10 mA cm−2 and a low Tafel slope of 43 mV dec−1 in an acidic medium of 0.5 M H2SO4. The enhanced bifunctional electrochemical performance of the MOF-D CoSe2 electrocatalyst has been attributed to the combination of a unique flower-shaped morphology with a plate-like nanoarchitecture, higher electrochemical active surface area and robust stability in both acidic as well as alkaline media.