Confinement of cobalt phosphides in nitrogen-doped carbon hosts for efficient peroxymonosulfate activation: Understanding charge-imbalance induced coordinative radical/non-radical oxidation

Abstract

Development of a new catalytic system with synergistic multiple active sites to effectively promote the activation of peroxymonosulfate (PMS) is crucial for the control of emerging organic pollutants in water, but it is still challenging. Herein, we explore robust CoPx-implanted porous N-doped carbon frameworks (CoPx@NC) to effectively activate PMS and eliminate tetracycline (TC). The cobalt phosphides in CoPx@NC spontaneously create the distinctive charge imbalance to form asymmetrically charged Coδ+ and Pδ− as dual active sites to efficiently enhance catalytic activity, while the positively polarized carbon induced by neighboring electronegative N atoms in CoPx@NC contributes to high catalytic efficiency in parallel. As an advanced catalyst, CoPx@NC displays excellent catalytic performances in PMS activation toward efficient TC degradation with an improved rate constant of 0.137 min−1 and a favorable k-value of 1.43 μmol s−1 g−1. Mechanistic analysis clearly unveils that the non-radical pathway (singlet oxygen 1O2 and direct electron transfer) in CoPx@NC/PMS system dominantly governs the TC degradation along with cooperative radical (SO4·− and ·OH) pathway. This study enriches the charge imbalance strategy for catalyst design and highlights a new catalytic platform to activate PMS for efficient pollutant degradation in water.