Abstract Emerging contaminants are toxic, persistent and non-biodegrade and have received extensive attention in recent years. Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) obtain high efficiency and can completely destruct the aqueous organic contaminants employing the generated reactive oxygen species (ROS). Metal oxides, especially those composed of mixed transitional metals, have exhibited remarkable catalytic performance in PMS activation. Transitional metal-based perovskites are one type of mixed metal oxides having tunable crystal structure and properties. The overlap of d orbitals of transitional metals in the B sites of perovskites with 2p orbitals of oxygen boosts the electron transfer between the adsorbed species, which can be achieved by tuning the spin state and transition metal-oxygen (TM-O) covalency in the structure of perovskites. These findings have been comprehensively investigated in the fields of oxygen reduction reaction (ORR) and electrocatalysis. However, PMS activation mechanisms in transitional metal-based catalytic systems are not fully illustrated. Herein, BaMn1-xCoxO3 (x = 0.2, 0.5, 0.8) perovskites were fabricated via the sol-gel method for PMS activation towards 4-chlorophenol degradation. Owing to the synergistic effect of Mn and Co, the as-synthesized BaMn1-xCoxO3 exhibited much higher catalytic activity than BaMnO3 and enhanced stability compared to that of BaCoO3. For BaMn0.5Co0.5O3, complete 4-chlorophenol can be achieved in 20 min. In-situ characterization combined with density functional theory calculation revealed that manipulating the Co substituting ratio fine-tuned the spin state of Mn in perovskites. Mn-Co sites with high spin state (low Co substitution ratio) favors PMS adsorption and promoted the electron transfer process. The types of generated ROS also changed by the modulation of Mn-Co spin states. BaMnxCo1-xO3 with smaller x generated more radicals, while non-radical pathway prevailed with high x ratios. These findings advance the understanding of transitional metal-based PMS activation and guide the synthesis of active transitional metal oxides for environmental remediation.

Electronic properties modulation in perovskite by transitional metal substitution for efficient peroxymonosulfate activation

ACS Spring 2022

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