Ultrathin 2D Co-MOF Showcasing Remarkable Electrocatalytic Oxygen Evolution Coupled with Unparalleled Stability

Abstract

Oxygen Evolution Reaction (OER) is typically carried out utilizing noble metals and metal oxides based nanostructures. Yet, due to their numerous drawbacks, including high cost, poor stability and negative environmental effects; researchers are driven to create new electro-active materials. To that end, we report an ultrathin 2D Co-MOF [Co₂(bpe)_2.5(NO₃)₄(CH₃O)] (Co-MOF) that crystallized under hydrothermal conditions, showing a terrific OER activity with an overpotential of 267 mV at the current density of 10 mA cm⁻² and the low Tafel slope value of 104 mV dec⁻¹. Two-dimensional MOFs offer numerous advantages over 3D MOFs such as better exposure and accessibility of active sites. The layered structure of 2D MOFs can provide greater structural flexibility, which can be beneficial for accommodating the changes during the OER process and maintaining structural integrity under operating conditions. The performance of Co-MOF surpasses commercially available OER catalyst RuO₂, demonstrating an unprecedented prolonged stability of 112 hours, which, to the best of our knowledge, represents the longest stability, observed for any pristine MOF to date. From the post-OER characterization, it was discovered that in situ formed species, Co(OH)₂ and CoOOH served as the active sites responsible for oxygen evolution.