Anchoring covalent organic polymers on supports with tunable functional groups boosting the oxygen reduction performance under pH-universal conditions

• Published in: Journal of colloid and interface science 2024-05, Vol.661, p.923-929
• Main Authors: Shu, Chonghong, Zhang, Wenlin, Zhan, Jiayu, Yu, Fengshou
• Format: Article
• Language: English
• Subjects: Charge redistribution; Covalent organic polymers; Electrochemical O2 reduction; Electron-withdrawing or electron-donating groups; pH-universal conditions
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2024.01.218

The FePc-based covalent organic polymers (COPFePc) polymerized in situ on the functionalized multiwalled carbon nanotubes (R-MWCNT) were synthesized (COPFePc/R-MWCNT, R = COOH, OH or NH2) for ORR under pH-universal conditions. The carbon nanotubes with electron-withdrawing or electron-donating groups induce charge redistribution around the active center Fe, tuning the ORR activity. The COPFePc/COOH-MWCNT catalyst exhibited an impressive ORR activity with half-wave potentials of 0.92, 0.78, and 0.72 V in alkaline, acidic, and neutral electrolytes, respectively. [Display omitted] Iron phthalocyanine (FePc) is an attractive nonprecious metal candidate for electrocatalytic oxygen reduction reaction (ORR). However, its low catalytic performance under acidic and neutral conditions limits its practical application. Herein, the FePc-based covalent organic polymers (COPFePc) polymerized in situ on the functionalized multiwalled carbon nanotubes (R-MWCNT) containing different electron-withdrawing or electron-donating groups (COPFePc/R-MWCNT, R = COOH, OH or NH2) were synthesized for ORR. Among them, COPFePc/COOH-MWCNT exhibited the best ORR performance under pH-universal conditions (acidic, neutral, and alkaline). Density-functional theory (DFT) calculations demonstrate that the electron-withdrawing or electron-donating effect of the functional groups in COPFePc/R-MWCNT causes charge redistribution of the active center Fe. The COOH functional group with an electron-withdrawing ability shifts the d-band center of Fe away from the Fermi energy level and reduces the binding strength of oxygen-containing intermediates, accelerating the ORR kinetics and optimizing the catalytic activity.