Halogen-assisted Ni based MOFs ball-flowers for enhanced electrocatalytic oxygen evolution

Although metal-organic framework (MOF) materials are now a hot candidate for improving the kinetics of the anodic oxygen evolution reaction (OER), direct application of them is challenging due to their poor intrinsic conductivity and internal active sites. Here, we successfully introduced halogen atoms into the octahedral topological structure of Ni based MOF materials, achieving an impressive improvement in OER activity. Accordingly, the as-obtained halogen-containing Ni based MOF ball-flowers (X-Ni-MOF BFs, X = F, Cl, Br and I) exhibit significantly enhanced electrocatalytic OER activity with an increase in electronegativity. The optimal F-Ni-MOF BFs possess an ultra-low overpotential of 222 mV at 10 mA cm−2, ∼70 mV lower than Ni-MOF nanosheets. Further research demonstrates that the introduction of halogen atoms can cause NiO6 octahedral distortion and strong electronic interactions between halogen and the adjacent Ni atoms, resulting in rapid reaction kinetics and lower electron transfer barriers. This work provides a reference for designing excellent electrocatalysts by adjusting their topological structure.