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Sufficient generation of H 2 O 2 played an essential role in boosting self-sufficient heterogeneous Fenton reaction. Herein, the dual H 2 O 2 production paths were designed to maximize the yield over H 2 O 2 -etched MoS 2 /FeS 2 Z-scheme heterojunction, whose surface was modified with abundant –OH groups and sulfur vacancies (SVs). Mechanism studies revealed that H 2 O 2 was generated via two-step single-electron reduction by electrons on conduction band, where H 2 O 2 production was significantly improved by the internal hole-scavenging effect from –OH groups. Additionally, electrons surrounding SVs served as another sites for H 2 O 2 production via one-step two-electron reduction even in darkness. H 2 O 2 yield in neutral aqueous solution reached 1.5 mM/g/h without external hole scavenger. Tetracycline and rhodamine B were effectively degraded under light or in darkness. The degradation performance was even comparable to the heterogeneous Fenton reaction. This work provides new insights for the design of self-sufficient heterogeneous Fenton system with exceptional degradation performance. [Display omitted] • E-MoS 2 /FeS 2 with abundant -OH groups and SVs is prepared via surface engineering. • H 2 O 2 yield is largely improved by the internal h+-scavenging effect from –OH groups. • e - surrounding SVs serve as another sites for H 2 O 2 production even in darkness. • In-situ H 2 O 2 yield reaches 1.5 mM/g/h, and it is enough for following Fenton reaction. • Pollutant can be degraded within 25 or 60 min under actual sunlight or in darkness. [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]

Fenton/photo-Fenton reaction was limited by slow Fe3+/Fe2+ cycle, low H 2 O 2 activation efficiency, and narrow applicable pH range. Here, Fe atoms doped MoS 2 (Fe–MoS 2) with abundant of low-valence Moδ+ (0 < δ < 4) was prepared. Benefiting from the powerful reduction capacity of Moδ+, the rate-limiting step of Fe3+ reduction was significantly accelerated. Nearly 100% of H 2 O 2 utilization efficiency was realized. Importantly, 90% of H 2 O 2 was effectively activated to be •OH. As a result, tetracycline degradation rate in photo-Fenton reaction catalyzed by Fe–MoS 2 was 5.8 and 4.2 times higher than those of MoS 2 and Fe–MoS 2 -Hyd (prepared by hydrothermal reaction). In comparison with MoS 2 and Fe–MoS 2 -Hyd whose efficient work range were limited in acidic condition, Fe–MoS 2 was a pH-universal catalyst (pH = 2.6–14.0) by taking advantage of the exposed Moδ+ and photoinduced electrons, largely improving the environmental tolerance. This work simultaneously addressed three bottlenecks in Fenton/photo-Fenton reaction, and provided a new strategy for the preparation of catalysts with powerful catalytic performance and high environmental adaptability. Low-valence Moδ+ sites were successfully exposed on Fe atoms doped MoS 2 surface. Benefiting from their powerful reduction capacity, the Fe3+/Fe2+ cycle rate was accelerated, the H 2 O 2 utilization efficiency and activation efficiency were maximized, and the applicable pH range was extended in photo-Fenton reaction. [Display omitted] • Fe–MoS 2 with abundant of exposed Moδ+ sites is prepared via surface engineering. • Moδ+ sites are favorable to generate Fe2+ sites and lower activation barriers of H 2 O 2. • Rate-limiting step, Fe3+/Fe2+ cycle, is accelerated by powerful reducibility of Moδ+. • 100% of H 2 O 2 utilization efficiency and 90% of activation efficiency are realized. • Applicable pH range of Fe–MoS 2 is extended to 2.6–14.0, wider than reference samples. [ABSTRACT FROM AUTHOR]