Self-Dissociation-Oriented Growth of Ultrathin Metal-Organic Framework Nanosheet Arrays for Efficient Oxygen Evolution

Metal-organic framework (MOF) ultrathin nano-sheets have attracted widespread attention for the oxygen evolution reaction (OER) due to their ultralow thickness and abundant coordinatively unsaturated metal atoms. Here, we first develop an in situ self-dissociation-oriented growth strategy to grow well-defined ultrathin Co-MOF and CoCu-MOF nanosheet arrays on Ni foam. By merely altering the dosage of the ligands, controlled nucleation and orientation growth of MOFs led to confined metal atom growth sites and ultrathin MOF nanosheets with a thickness of only about 2.5 nm. Subsequent pyrolysis treatment in the N2 atmosphere transforms the ultrathin 2D Co-MOF nanosheets into CoCN and CoCuCN electrocatalysts, which can be directly used as highly active OER electrodes. Remarkably, CoCN and CoCuCN exhibit excellent OER activity at low overpotentials of 231 and 196 mV to deliver a current density of 10 mA cm-2 and long-term stability with negligible decay even after 20 h continuous electrolysis, outperforming most state-of-the-art noble-metal-free and Co-based OER electrocatalysts to date. This study sheds light on the in situ self-dissociation-oriented growth strategy to achieve high-performance ultrathin MOF-based electrocatalysts and provides an advanced pathway to controllably fabricate other types of ultrathin MOF arrays uniformly.