Ultrafine cucurbit[n]uril (n = 5-8)-Ni nanocomposites as highly efficient catalysts for electrocatalytic oxygen evolution reaction

Abstract

Nickel-based oxygen evolution reaction (OER) electrocatalysts have garnered significant attention due to their high catalytic activity and abundant reserves. In this study, we reported a series of cucurbit[n]urils (CB[n], n = 5-8) functionalized Ni nanocomposites (CB[n]-Ni, n = 5-8) to synergistically enhance the OER catalytic activity in alkaline media. The sizes and electronic structures of CB[n]-Ni can be precisely controlled by CB[n] with varying cavity sizes. Among these CB[n]-Ni, CB[7]-Ni presented superior OER performance compared to other CB[n]-Ni (n = 5, 6, 8) and CB-free Ni nanocomposites. Operando electrochemical impedance spectroscopy (EIS) studies demonstrated that CB[7]-Ni initiated OER at a relatively low applied potential of 1.5 V vs. RHE. Additionally, spectroscopic measurements and theoretical calculations revealed that the incorporation of CB[7] regulates the electronic structure of the active Ni nanocomposite, lowered the activation energy for the formation of *OOH intermediate, thereby facilitating the OER porcess. This work not only broadens the application of supramolecular macrocycles in electrocatalysis but also provides a novel strategy for the design of electrocatalysts.