Ni(II)-Incorporated Ethylene Glycol-Linked Tetraphenyl Porphyrin-Based Covalent Organic Polymer as a Catalyst for Methanol Electrooxidation

Abstract

Methanol oxidation reaction (MOR) is a perfect alternative to the conventional oxygen evolution reaction (OER), generally utilized as the anode reaction for hydrogen generation via the electrochemical water splitting method. Moreover, MOR is also relevant to direct methanol fuel cells (DMFCs). These facts motivate the researchers to develop economical and efficient electrocatalysts for MOR. Herein, we have introduced an ethylene glycol-linked tetraphenyl porphyrin-based (EG-POR) covalent organic polymer (COP). The Ni­(II)-incorporated EG-POR material Ni-EG-POR displayed excellent OER and MOR activities in an alkaline medium. The materials were thoroughly characterized using 13C solid-state NMR, Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) surface area analyzer, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analyzer (TGA), and powder X-ray diffraction (PXRD) techniques. These organic–inorganic hybrid materials showed high chemical and thermal stability. Ni-EG-POR requires an overpotential of 400 mV (vs RHE) in OER and 190 mV (vs RHE) in MOR to achieve a current density of 10 mA cm–2. In addition, the catalyst also showed excellent chronoamperometric and chronopotentiometric stability, indicating that the catalyst can provide stable current over a longer period and its potential as a non-noble metal MOR catalyst.

Non-Noble-Metal-Based Porphyrin Covalent Organic Polymers as Additive-/Annealing-Free Electrocatalysts for Water Splitting and Biomass Oxidation

“…However, they often suffer severe disadvantages like poor stability, lower availability of electrochemical active sites, and dissolution of the catalyst in the electrolyte . Therefore, the heterogenization of single-molecule metalloporphyrins could be an effective strategy to develop an efficient electrocatalyst. − …”

Visible-Light-Driven Reduction of CO2 to CO with Highly Active and Selective Earth-Abundant Metal Porphyrin-Conjugated Organic Polymers

“…The construction of COPs containing a metalloporphyrin group is a perfect strategy to address these issues. COPs containing metalloporphyrins integrate the properties of both metalloporphyrins and COPs, providing possibilities for efficient photocatalytic CO 2 conversion and electrocatalytic performance such as the methanol oxidation reaction, hydrogen evolution reaction, and oxygen evolution reaction. , Specifically, these properties are the excellent light-collecting ability of metalloporphyrins, which improves sunlight utilization, and the large π-conjugated system, which affords preorganized channels for rapid charge-carrier separation and transport. ,− For example, a Co(II)-porphyrin-functionalized conjugated polymer assembled by Sonogashira cross-coupling was reported by Yu et al as an active nonhomogeneous catalyst for CO 2 photoreduction . Furthermore, o -phenanthroline is a N-rich ligand that provides abundant active sites.…”

Quaternization of a Triphenylamine-Based Conjugated Porous Organic Polymer to Immobilize PtCl62– for the Photocatalytic Reduction of 4-Nitrophenol

“…One efficient approach to address this issue is utilizing suitable porous supports to anchor MNPs, which increases their dispersity in the whole supports to avoid the formation of larger nanoparticles; thus, the development of suitable supports is of paramount significance. Up to now, various supports including inorganic materials, , metal–organic frameworks, − organic molecular cages, − etc. have been developed, but these supports are still restricted owing to the weak interaction between supports and MNPs, which decreases the chemical stability of the photocatalyst. − Moreover, another point most previous works have ignored is whether the introduction of support has broadened the light absorption region and improved the light absorption ability of the photocatalyst, which also highly influences the final conversion efficiency.…”