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By taking advantage of in-situ generated H 2 O 2 , Z-scheme Fe 2 (MoO 4) 3 /Ag/Ag 3 PO 4 heterojunction displayed outstanding degradation performance. [Display omitted] • Internal-electric-field is built at interface, resulting in a Z-scheme routine of e - • k of Fe 2 (MoO 4) 3 /Ag/Ag 3 PO 4 is 254 and 7.0 times than those of Fe 2 (MoO 4) 3 and Ag 3 PO 4. • H 2 O 2 is activated on Fe 2 (MoO 4) 3 for •OH, avoiding quenching effect on h + and e - • k is improved by 1.7 times via turning waste (H 2 O 2) into wealth (•OH) • 91.2% of removal efficiency is remained after 5 runs, while that of Ag 3 PO 4 is 68.1% Ag 3 PO 4 -based photocatalysts have been deeply studied in environmental remediation; however, two problems limited their further application: photocorrosion and quenching effect by in-situ generated H 2 O 2. To addressed these two questions simultaneously, Fe 2 (MoO 4) 3 was coupled with Ag 3 PO 4 to construct Z-scheme Fe 2 (MoO 4) 3 /Ag/Ag 3 PO 4 heterojunction driven by internal-electric-field. The rhodamine B degradation rate of heterojunction was 254 and 7.0 times higher than those of Fe 2 (MoO 4) 3 and Ag 3 PO 4 , respectively. The outstanding photoactivity was due to the high visible-light harvest, low interface resistance, high separation efficiency of charge carriers, long lifetime of hole (h +) and electron (e -), well-preserved oxidation potential of h +, and especially photocatalytic produced H 2 O 2 inside the system. The in-situ generated H 2 O 2 was fully activated to be •OH on the Fe 2 (MoO 4) 3 surface via a Fenton reaction, leading to the elimination of quenching effect on h + and e -, and generation of more •OH. Additionally, in Z-scheme heterojunction, e - transferred from Ag 3 PO 4 to Fe 2 (MoO 4) 3 , avoiding the accumulation on Ag 3 PO 4 surface, and hence suppressing the photocorrosion. As a result, 91.2% of degradation efficiency remained after 5 cycles. This paper provides a new method to simultaneously increase the degradation rate by utilizing the in-situ generated H 2 O 2 and improve the stability of Ag 3 PO 4 via constructing a Z-scheme heterojunction. [ABSTRACT FROM AUTHOR]

• FeCo@nitrogen-doped graphitized carbon (NGC) composite was synthesized in one-step. • rate constant in microwave (MW) assisted Fenton reaction was as high as 2.0 min−1. • Extra 288% of removal efficiency was yield in peroxymonosulfate+MW+FeCo@NGC system. • Contribution of thermal effect was 65% ± 7% for malachite green removal. • Co3+/2+ leaching in FeCo@NGC was only one-tenth of that in pure FeCo. As an efficient non-precious metal catalyst, FeCo alloy was widely used in various catalytic reactions. Owing to the organic pollution in ecosystem, it has attracted much attention in heterogeneous Fenton reaction. Unfortunately, their application was restricted by slow process and high leaching. To overcome these shortcomings simultaneously, herein, FeCo@nitrogen-doped graphitized carbon (NGC) core/shell composite was synthesized via one-step annealing Prussian blue analogue. In microwave assisted Fenton reaction (MAFR), malachite green (MG) degradation time was only 2.5 min, and the rate constant was 2.0 min−1, about 20 times higher than heterogeneous Fenton reaction. Synergistic index was 3.88, meaning extra 288% of removal efficiency was yield in peroxymonosulfate (PMS)+MW+FeCo@NGC system. The effect of microwave-activation was divided into thermal effect and non-thermal effect. SO 4 ·− produced through thermal effect occupied 73% ± 8% of total number. The contribution of thermal effect was estimated to be 65% ± 7% for MG removal. Non-thermal effect was clarified by hotspots effect theory. Due to protection of NGC shell, Co3+/2+ leaching in composite was only one-tenth of pure FeCo. FeCo@NGC composite could be rapidly recycled due to ferromagnetic behavior with saturation magnetization of 98.7 emu/g. 89.3% of degradation efficiency was maintained after the 5th cycle. [ABSTRACT FROM AUTHOR]

• Formation mechanism of "brick-like" Fe 2 (MoO 4) 3 /MoO 3 heterojunction is investigated. • Inner electric field built at interface is beneficial for Z-scheme path of electron. • H 2 O 2 acts as oxidant in Fenton reaction and e - scavenger in photocatalytic reaction. • k is 0.107 min−1 in photo-Fenton reaction, 170 times higher than photocatalysis. • 1140% of extra efficiency is yielded by coupling Fenton reaction and photocatalysis. Fe 2 (MoO 4) 3 /MoO 3 heterojunction was prepared by a grinding-calcination method, and they displayed rapid degradation performance in photo-Fenton reaction. [Display omitted] The photo-Fenton reaction consisted of photocatalytic reaction and heterogeneous Fenton reaction is an effective technique for pollutant degradation, because the degradation rate is faster than individual reactions. In this work, Fe 2 (MoO 4) 3 /MoO 3 heterojunction was prepared via a grinding-calcination method. Work function measurement indicated that the inner electric field was build at the interface between Fe 2 (MoO 4) 3 and MoO 3 , leading to a Z-scheme electron (e -) transfer pathway, and this result was supported by the radical quenching experiment and band structure analysis. In photo-Fenton reaction, the degradation rate was 57 and 170 times higher than those in heterogeneous Fenton reaction and photocatalytic reaction, respectively. This improvement was because H 2 O 2 not only served as an oxidant in heterogeneous Fenton reaction, but also acted as scavenger of e - in photocatalytic reaction. Synergistic effect was established between heterogeneous Fenton reaction and Z-scheme photocatalytic process via H 2 O 2 as a medium, and 1140% extra degradation efficiency was yielded by coupling these two reactions together. Besides high activity, 92.6% of degradation efficiency was remained after the 5th cycle, indicating an outstanding recyclability. [ABSTRACT FROM AUTHOR]

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]