Regulating coordination environment in metal-organic Framework@Cuprous oxide Core-Shell catalyst for Promoting electrocatalytic oxygen evolution reaction.

ABSTRACT

As a kind of promising oxygen evolution reaction (OER) catalysts, metal-organic frameworks (MOF) are often constrained by their inherent poor electroconductivity and structural instability. In this study, we developed a mono-dispersed zeolitic imidazolate framework-67@cuprous oxide (ZIF-67@Cu2O) core-shell catalyst via in-situ growth method for highly efficient alkaline OER. The ZIF-67@Cu2O shows an excellent OER activity with a low overpotential of 254 mV at 10 mA cm-2 and Tafel slope of 87.9 mV·dec-1 in 1.0 M KOH. Furthermore, the ZIF-67@Cu2O also shows a high turnover frequency (TOF) of 0.166 s-1 at 1.60  V vs. RHE and long-term stability for 160 h at a high current density of 100 mA cm-2. The unique core-shell structure with the Cu2O core linked with ZIF-67 shell through interfacial di-oxygen bridge improves the structural stability, enhances the charge transfer, and provides more active sites. Moreover, the interfacial coordination structure was regulated from Co-N4 to Co-N2O2 which elevates the valence of Co sites and optimizes the adsorption free energy of oxygen-containing intermediates, thus improving the electrocatalytic OER performance. This work could propose the way for designing novel MOF-based nanomaterials and developing desirable and robust heterogeneous OER catalysts.