Ultrafine cucurbit[n]uril (n = 5–8)–Ni nanocomposites as highly efficient catalysts for the 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 report a series of cucurbit[n]uril (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 using CB[n] with varying cavity sizes. Among these CB[n]–Ni nanocomposites, CB[7]–Ni presented superior OER performance compared to other CB[n]–Ni (n = 5, 6, and 8) and CB-free Ni nanocomposites. Operando electrochemical impedance spectroscopy (EIS) studies demonstrated that CB[7]–Ni initiated the OER at a relatively low applied potential of 1.5 V vs. RHE, achieving a superior turnover frequency of 0.24 s⁻¹ at 1.55 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 and lowers the activation energy for the formation of the *OOH intermediate, thereby facilitating the OER process. This work not only broadens the application of supramolecular macrocycles in electrocatalysis but also provides a novel strategy for the design of electrocatalysts.