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At present, yolk@shell nanoreactor has drawn much attention in Fenton reaction, since the degradation rate could be accelerated by confinement effect, and metal leaching could be suppressed under the shell protection. To further improve the performance of traditional yolk@shell nanoreactor with single core, in this work, a yolk@shell nanoreactor with multiple CoFe nanoparticles as cores and nitrogen-atom doped carbon (NC) as shell was prepared. In peroxymonosulfate (PMS)-based Fenton-like reaction, 93.8 % of degradation efficiency was realized within 30 min over CoFe@NC, much better than the reference broken CoFe@NC (B-CoFe@NC), confirming the positive function of integrated yolk@shell structure. Based on the radical trapping experiment, 1O 2 was the most important reactive oxygen species in CoFe@NC, while SO 4 •- played a dominated role in B-CoFe@NC, reflecting the different catalytic mechanism in these two catalysts. To reveal the confinement effect, electron paramagnetic resonance analysis was carried out to trace the 1O 2 source. And they were originated from SO 4 •- and •OH with high concentrations inside the yolk@shell CoFe@NC nanoreactor. This study provided a novel method to construct yolk@shell nanoreactor with multiple cores and gave a novel insight on enhanced Fenton-like performance via confinement effect. [Display omitted] • Yolk@shell nanoreactor with multiple cores is prepared for Fenton-like reaction. • MB removal rate of CoFe@NC is 0.086 min−1, superior than reference samples. • Leached Co and Fe ions are 0.48 and 0.04 mg/L under NC shell protection. • Conversion from SO 4 •- and •OH to 1O 2 is accelerated by confinement effect. • CoFe@NC nanoreactor displays good environment adaption and recyclability. [ABSTRACT FROM AUTHOR]

In peroxymonosulfate (PMS)-based Fenton-like reaction, there were two pathways for PMS activation: radical path on transition metal surface and non-radical path on heteroatom-doped carbon surface. In this work, CoS 2 /nitrogen-atom doped carbon (NC)@SiO 2 yolk@shell nanoreactor was designed, on CoS 2 /NC surface, these two paths performed parallelly inside the nanoreactor, leading to an accelerated tetracycline degradation rate. 90.9% of removal efficiency was realized within 15 min, much higher than the reference samples, and the advantages of yolk@shell nanoreactor were illustrated in detail. Moreover, benefiting from the SiO 2 shell protection, the leached cobalt ion was only 0.27 mg/L, which was 1/20 of the reference CoS 2 /NC without SiO 2 shell. During the mechanism study, the two activation paths were identified by electron paramagnetic resonance tests, radical trapping experiments and electrochemical tests, where the SO 4 •- and 1O 2 were responsible for tetracycline (TC) degradation. This study provided a new strategy to simultaneously accelerate radical activation path and non-radical activation path by using the yolk@shell nanoreactor, and it might inspire other high efficient catalyst design for PMS-based Fenton-like reaction. [Display omitted] CoS 2 /NC@SiO 2 yolk@shell nanoreactor with CoS 2 /NC nanoparticles encapsulated inside the SiO 2 shell was prepared as a catalyst in Fenton reaction. • Radical and non-radical PMS activation paths are confined in CoS 2 /NC@SiO 2 nanoreactor. • Removal rate of CoS 2 /NC@SiO 2 is 3.6×10−2 L·min·mg−1, better than reference samples. • Co3+/2+ leaching is lowered to 0.27 mg/L due to the SiO 2 shell protection. • SO 4 •- and 1O 2 are responsible for TC degradation, and catalytic mechanism are studied. • Nanoreactor shows good versatility, recyclability, and anti-interference ability. [ABSTRACT FROM AUTHOR]

At present, nitrogen-rich graphitic carbon nitride (g -C 3 N 5) has emerged as an alternative for traditional graphitic carbon nitride (g -C 3 N 4), due to better visible-light utilization efficiency and abundant surface functional groups. In this paper, a g -C 3 N 5 /MXenes (Ti 3 C 2) binary heterojunction was prepared and used as a photocatalyst in environmental remediation. In tetracycline (TC) degradation, g -C 3 N 5 /Ti 3 C 2 displayed better performance than those of the reference photocatalysts, including g -C 3 N 5 , g -C 3 N 4 , Ti 3 C 2 and g -C 3 N 4 /Ti 3 C 2. The underlying electron (e -) transfer mechanism was investigated in detail. Besides higher visible-light harvest, better separation efficiency of photo-induced charge carrier and lower surface resistance, an internal-electric-field was established at the interface between g -C 3 N 5 and Ti 3 C 2 , and the driving force for e - transfer was 93.9 mV. hole (h +), 1O 2 , •OH and •O 2 - were involved into TC degradation, where h + played a dominating role due to the high e - transfer efficiency. Benefiting from the good photothermal effect, g -C 3 N 5 /Ti 3 C 2 could efficiently transfer solar energy to thermal energy, leading to the high temperature of catalyst surface and acceleration of the surface degradation reaction rate. This work provided a possibility to construct a g -C 3 N 5 -based visible-light photocatalyst to efficiently degrade the persistent organic contaminants. [Display omitted] • Ti 3 C 2 served as a reservoir for e - transfer from the conduction band of g -C 3 N 5. • Degradation rate of g -C 3 N 5 /Ti 3 C 2 is 2.5 times higher than that of g -C 3 N 4 /Ti 3 C 2. • Internal-electric-field is formed, and the driving force for e - transfer is 93.9 mV. • h +, 1O 2 , •OH and •O 2 - are involved into degradation, the contribution of h + is 82.8%. • g -C 3 N 5 /Ti 3 C 2 shows a better photothermal effect than g -C 3 N 4 /Ti 3 C 2 and g -C 3 N 5. [ABSTRACT FROM AUTHOR]

• Co-CeO 2 fits Langmuir model and pseudo second order kinetics, Q m is 1.92 times higher than CeO 2. • Degradation rate of Co-CeO 2 is 6.7 times higher than CeO 2. • Degradation is an endothermic and non-spontaneous process with E a of 35.3 kJ/mol. • Catalytic mechanism is revealed, and •OH, SO 4 •- and 1O 2 are involved in degradation. • 77.1% of efficiency remains after 5 runs, Co ions leaching is 12 times lower than Co 3 O 4. [Display omitted] Co-CeO 2 nanoflower was prepared via a solvothermal-calcination process. Compared to CeO 2 , the maximum adsorption capacity increased by 1.92 times, and the tetracycline degradation rate was enhanced by 6.7 times. In Fenton-like reaction, adsorption and degradation are inseparable processes. The pollutants were enriched on the surface of catalyst by adsorption leading to the increase of the local concentration, and this was beneficial for acceleration of the degradation rate. Therefore, a catalyst with high adsorption capacity, low metal leaching and rapid activation rate toward peroxymonosulfate (PMS) was highly desirable. In this paper, Co-doped CeO 2 (Co-CeO 2) nanoflower was prepared via a solvothermal-calcination process. The nanoflower with a hierarchical porous structure was made up of dozens of nanosheets. Compared to CeO 2 , more Ce(Ⅲ) sites and defects were generated on Co-CeO 2 surface, and the maximum adsorption capacity was increased by 1.92 times. Benefiting from the high activity of Co toward the activation of PMS, the degradation rate was enhanced 6.7 times. The major radicals were determined and the corresponding degradation mechanism was revealed. Additionally, Co-CeO 2 nanoflower was demonstrated to be high efficient in many persistent organic pollutant degradation and also exhibited outstanding reusability after several cycles. Moreover, the leaching of toxic Co ions was 12 times lower than the referenced Co 3 O 4. This work provides a promising approach on rational design a catalyst with high adsorption property and degradation efficiency in Fenton-like reaction for environmental remediation. [ABSTRACT FROM AUTHOR]

• Internal-electric-field is built at interface, resulting in a Z-scheme routine of e -. • TC is degraded within 40 min, and k of photo-Fenton reaction is 4.5 × 10−2min−1. • k of photo-Fenton reaction is higher than sum of Fenton reaction and photocatalysis. • Contribution of radicals in TC removal follows the order: •OH surf >•O 2 ->1O 2 > h +>•OH free. • 93.6% of the degradation efficiency of the 1st cycle is maintained after 5 cycles. A Z-scheme heterojunction with sandwich-like structure was prepared. It displayed high degradation efficiency and magnetic recyclability in photo-Fenton reaction, and the catalytic mechanism was carefully investigated. [Display omitted] Herein, the sandwich-like Fe 3 O 4 @FeS 2 @C@MoS 2 composite was prepared via coating MoS 2 shell on the surface of core/shell Fe 3 O 4 @C composite. During the coating process, Fe 3 O 4 was partly sulfurized to FeS 2 , whose energy band was well-matched with that of MoS 2 for a Z-scheme heterojunction. The residual Fe 3 O 4 ensured the rapid separation of heterojunction by magnet. In photo-Fenton reaction, 81.5% of tetracycline was degraded within 40 min, which was higher than the sum of degradation efficiency of Fenton reaction and photocatalytic reaction. 93.6% of the degradation efficiency in the 1st cycle was still maintained after 5 cycles. In mechanism study, the sources of •OH, •O 2 -, 1O 2 and h + were carefully traced, and the contributions of these radicals followed the order: •OH surf >•O 2 ->1O 2 > h +>•OH free. An inner electric field was built at the interface by analyzing the energy band and work functions, which driven the charge carriers transfer followed a Z-scheme path. The findings in this manuscript were beneficial for designing catalysts with high photo-Fenton activity. [ABSTRACT FROM AUTHOR]