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[Display omitted] Increasing water pollution has imposed great threats to public health, and made efficient monitoring and remediation technologies critical to a clean environment. In this study, a versatile heterojunction of Au nanoparticles modified phosphorus doped carbon nitride (Au/P-CN) is designed and fabricated. The Au/P-CN heterostructure demonstrates improved light absorption, rapid separation of charge carriers, and improved electrical conductivity. Taking the toxic 4-chlorophenol (4-CP) as an example, an ultrasensitive photoelectrochemical (PEC) sensor is successfully demonstrated, exhibiting a wide linear range (0.1–52.1 μM), low detection limit (∼0.02 μM), significant stability and selectivity, as well as reliable analysis in real samples. Moreover, efficient photocatalytic degradation with a high removing efficiency (∼87%) toward 4-CP is also achieved, outperforming its counterpart of Au nanoparticles (NPs) modified graphitic carbon nitride (Au/g−CN, ∼59%). This work paves a new way for efficient and simultaneous detection and remediation of organic pollutants over versatile photoactive catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel nitrogen-doped graphene cubes (NGCs) were synthesised. • The lightweight NGCs were employed for sulfamethoxazole (SMX) degradation. • Identification of reactive oxygen species was conducted. • Comprehensive mechanistic studies on SMX degradation were performed. As a sustainable and green approach, carbocatalysis, a metal-free strategy, has shown exceptional results in advanced oxidation processes (AOPs). Nonetheless, the recovery of these catalysts has been a major shortcoming over the years. Herein, three-dimensional nitrogen-doped graphene macrostructures (3D-NGMs), in the form of macro cubes, were synthesised by a simple cross-linking and thermal annealing procedure, after which they were employed in the activation of peroxydisulfate (PS) for the degradation of sulfamethoxazole (SMX). The catalytic cubes were loaded with different amounts of nitrogen precursor to investigate the role of nitrogen configuration in the sp2 hybridised carbon network on AOPs. NGC3 cubes with optimum N-loading exhibited outstanding performance for SMX degradation owing to their optimum N/C ratio. Various reaction parameters were studied to optimise the catalytic system. Comprehensive studies on the radical generation were done and illustrated the dominance of the non-radical pathway leading to the proposal of a possible reaction mechanism for SMX. This study not only suggests the role of nitrogen doping on graphene macrostructures but also provides novel insights into macro catalysis to overcome the recovery challenges posed by nano catalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen-doped reduced graphene oxide beads (NrGOb) were fabricated by a one-step self-assembly strategy. • The lightweight NrGOBs and peroxymonosulfate system presented high activity in oxidative degradation of organic pollutants. • The catalytic beads were packed in a fixed-bed column reactor to maintain a continuous process. • Reactive radicals were identified by the quenching tests and electron paramagnetic resonance spectra. • Mechanistic studies on peroxymonosulfate activation and degradation pathways of hydroxybenzoic acid were performed. Metal-free graphene-based catalysts have demonstrated excellent performance in advanced oxidation processes (AOPs). However, the recovery and reusability of these nanocatalysts are still a major issue. In this study, three dimensional (3D) nitrogen-doped reduced graphene oxide beads (NrGOb) were synthesized via a self-assembly method and then applied in heterogeneous activation of peroxymonosulfate (PMS) for the oxidation of hydroxybenzoic acid (HBA). The materials (NrGOb) were annealed at various temperatures ranging from 500 to 1000 °C, and the resulting NrGOb derived from 800 °C (NrGOb-800) exhibited the best performance for PMS activation. To avoid the challenging recovery, the degradation experiments were also performed in a packed-bed catalytic reactor. Various reaction parameters were investigated to optimize the efficiency of the system. Electron paramagnetic resonance (EPR) and quenching tests were carried out to differentiate the contribution of reactive radicals (SO 4 •- and •OH) in the degradation process and then aided in illustrating the degradation mechanism. Finally, the stability and reusability of the catalytic beads were investigated. The efficiency slightly declined with increased cycles; however, catalyst regeneration would be able to partially restore the active sites. The results suggest the feasibility of exploiting graphene-based macrostructures on the AOPs platform for the degradation of organic pollutants in commercial wastewater treatment plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single atom Cu in the configuration of Cu-N 3 was anchored on hollow spherical g-C 3 N 4 to form SACu- hs CN. • The acetaminophen degradation activity of SACu- hs CN was superior to the sample of AGCu- hs CN with aggregated Cu particles via H 2 O 2 activation. • The SACu- hs CN/H 2 O 2 system degraded acetaminophen with a good durability. • 1O 2 unusually played a dominant role in degradation rather than the common OH radicals. Discharge of recalcitrant pharmaceuticals into aquatic systems has caused severe impacts on public health and ecosystem. Advanced oxidation processes (AOPs) are effective for eliminating these refractory pollutants, for which single-atom catalysts (SACs) become the state-of-the-art materials owing to the maximized exposure of active metal sites. In this work, hollow spherical graphitic carbon nitride (hs CN) was fabricated to incorporate copper species to develop Fenton-like catalysts for acetaminophen (ACT) removal. Through pyrolysis of supramolecular assemblies derived from melamine-Cu complex and cyanuric acid, single atom Cu-N 3 sites were anchored on hs CN by N-coordination to obtain SACu- hs CN. In virtue of the atomically dispersed Cu-N 3 sites as well as the hollow structure of hs CN providing smooth channels for the interactions between single Cu atoms and reactants, the optimal 5.5SACu- hs CN removed 94.8% of ACT after 180 min of Fenton-like reactions, which was superior to that of 5.5AGCu- hs CN with aggregated Cu particles on hs CN (56.7% in 180 min). Moreover, 5.5SACu- hs CN was still active after four cycles of regeneration. The mechanism investigation demonstrated that both hydroxyl radicals (OH) and singlet oxygen (1O 2) contributed to ACT degradation in 5.5SACu- hs CN/H 2 O 2 system, in which non-radical 1O 2 played the dominant role. [ABSTRACT FROM AUTHOR]

Various MnO x phases and crystals were investigated in peroxymonosulfate (PMS) activation for oxidation of aqueous phenolic pollutants. MnO x with controlled crystal structure (α, β, γ, and amorphous-MnO 2) and redox states (Mn 2 O 3 , and MnO) can induce different oxidative pathways toward organic polymerization against degradation in acidic conditions. Surface MnⅡ (s) and MnⅢ (s) of MnO x tend to bond with PMS to generate confined Mn(Ⅱ, Ⅲ) (s) − (HO)OSO 3 − complexes to initiate a nonradical electron-transfer pathway (ETP). Meanwhile, high-valence MnⅣ (s) in MnO x will directly attack micropollutants and spontaneously be reduced to low-valence states (MnⅡ (s) and MnⅢ (s)) to initiate ETP. Mn 2 O 3 can activate PMS to generate other radical species for mineralization. ETP will selectively initiate one-electron abstraction of phenol molecules into monomer phenoxy radicals and polyphenols on catalyst surface. Thus, manganese crystal structures will govern the surface redox species to induce multiple oxidation pathways toward different polymer products for water decontamination and carbon recycle. [Display omitted] • MnO x catalysts induce organic polymerization/degradation by peroxymonosulfate (PMS). • Crystallinity and valence states of MnO x determine the reaction mechanism and routes. • Low valent Mn species tend to cause electron-transfer pathways (ETPs). • ETPs were responsible for the polymerization while radicals for degradation. [ABSTRACT FROM AUTHOR]