Self-dissociation-assembly of ultrathin metal-organic framework nanosheet arrays for efficient oxygen evolution

Two-dimensional metal-organic frameworks (MOFs) are promising earth-abundant electrocatalysts, especially for the key process of oxygen evolution reaction (OER), but challenges remain in the lack of effective synthesis and stabilization strategies. Here we first develop a general self-dissociation-assembly (SDA) strategy for in situ synthesis of well-defined ultrathin CoNi-MOF nanosheet arrays (CoNi-MOFNA) as highly active OER electrode. Remarkably, CoNi-MOFNA exhibit excellent OER activity and long-term stability, which deliver the current density of 10 mA cm−2 at a low overpotential of 215 mV with negligible decay even after 300 h continuous electrolysis. The mass activity of CoNi-MOFNA is 14-times higher than commercial RuO2. In addition, the systematic electrochemistry and time-dependent XAS spectroscopy studies convincingly identify the OER active sites of coordinatively unsaturated metal nodes and uncover the structure evolution of CoNi-MOFNA. More importantly, we have demonstrated the universality of this significant SDA strategy for controllably fabricating other types of ultrathin MOF nanosheet arrays uniformly on diverse metal substrates.