Controllable synthetic strategy of the coordinatively unsaturated metal sites on Ni-BTC for highly efficient oxygen evolution

Abstract

Metal-organic frameworks (MOFs) have been regarded as promising OER catalyst candidates, while synthetic strategies were used to enhance the OER performance of MOFs. The coordinatively unsaturated metal sites (CUMSs) are recognized as the important active sites on MOFs. Herein, the CUMSs of nickel-based MOF (Ni-BTC) were successfully tuned by glow discharge plasma in room temperature. The electron etching strategy controlled the concentration of CUMs and remained the main structure due to the low temperature and adjustable parameters. The electrochemical activity of the Ni-BTC by is correlated with the abundance of CUMSs. Specifically, Ni-BTC-500–5 obtained by plasma etching 5 min shows a highest catalytic activity of OER, which exhibits a low overpotential (347 mV at 100 mA·cm-2), low Tafel slope (37 mV·dec-1), and large double layer capacitance (22.0 mF·cm-2). The mechanism of plasma etching and the role of CUMs are also discussed.