Electrocatalytic Oxygen Reduction Reaction Using a Water-Stable Ni-Based Coordination Polymer with Two-Dimensional Honeycomb Architecture

Abstract

A new Ni(III)-based metal-organic coordination polymer (MOCP) of formula [Ni(4,4 '-IPDPA)1.5(H2O)3]& centerdot;6H2O (4,4 '-IPDPA = 4,4 '-isopropylidenediphenoxyacetate), 1, has been synthesized at ambient temperature using the slow layer diffusion method. The framework of compound 1 was obtained through single-crystal X-ray diffraction (SCXRD). It was comprehensively analyzed by various methods, including powder X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), ultraviolet-visible (UV-vis) spectroscopy, luminescence spectroscopy, Brunauer-Emmett-Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). Compound 1 shows promising electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline conditions. With a nearly four-electron reduction mechanism and a half-wave potential of 0.72 V versus a reversible hydrogen electrode (RHE), compound 1 exhibits remarkable ORR performance. The compound 1 most intriguingly showed good long-term stability. In addition to the presence of accessible pores within the framework, the emergence of the reduced Ni(II) moiety from Ni(III) during cathodic polarization is believed to be responsible for the high level of activity. Compound 1 also demonstrated exceptional resistance toward methanol poisoning during the ORR activity. Moreover, the density functional theory (DFT) analysis suggests that the as-prepared Ni3+-ion-based MOCP follows the four-electron-guided ORR pathway with the formation of *O intermediate as the potential-determining step (PDS).