In situ decomposition of metal-organic frameworks into ultrathin nanosheets for the oxygen evolution reaction

The oxygen evolution reaction (OER) is a pivotal process for water-splitting and many other energy technologies involving oxygen electrodes. Herein, a new synthesis strategy is proposed to prepare OER catalysts based on a simple yet flexible in situ decomposition of Co-based acetate hydroxide metal-organic frameworks (MOFs). This process allows straightforward fabrication of various 2D hydroxide ultrathin nanosheets (UNSs) with excellent component controllability. The as-obtained Co-based hydroxide UNSs demonstrate superior catalytic activity for the OER due to the exposure of numerous active sites. In particular, the CoNi hydroxide UNSs exhibit low overpotentials (η) of 324 and 372 mV at current densities of 10 and 100 mA·cm^–2, respectively; a large turnover frequency (TOF) of 0.16 s^–1 at η = 380 mV; and a small Tafel slope of 33 mV·dec^–1 in an alkaline environment. Importantly, these values are superior to those of the state-of-theart IrO₂ commercial electrocatalyst. This facile strategy enables the exploration of more efficient and economic OER electrocatalysts with various constituents and opens a promising avenue for large-scale fabrication of functional nanocatalysts for use in clean energy technologies.