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[Display omitted] • Overview of fundamentals of Nb 2 O 5 as photocatalyst-structure and properties. • Heterojunction photocatalysts -Z and S scheme- charge transfer routes. • Recent advances in Nb 2 O 5 based heterojunctions for photocatalytic applications. • Strategies for improving the photocatalytic performance Nb 2 O 5 based heterojunctions. Significant advancements in the field of photocatalysis in recent years have highlighted the heterojunctions based on Nb 2 O 5 as a focal point of research. This comprehensive review diligently analyses the progress in Nb 2 O 5 -based heterojunctions for their application in photocatalysis, focusing on synthesis, characteristics and their pivotal role in addressing crucial energy and environmental challenges. The review emphasizes the fundamental principles of photocatalysis in pollutant removal and H 2 generation, elucidating key processes such as light absorption, charge generation and surface reactions. The different types of heterojunctions, their basic principles and role in enhancing the charge separation and overall photocatlytic performance have been discussed. The recent advances in Nb 2 O 5 -based heterojunctions are extensively discussed for the photocatalytic applications such as pollutants removal and H 2 evolution. Furthermore, the review delves into strategies employed to enhance the photocatalytic activity of Nb 2 O 5 -based heterojunctions such as doping, oxygen vacancies modification, morphological engineering and atomic control, as well as loading with support materials. Each strategy is explained, emphasizing its impact on charge separation and overall efficiency. The review concludes by highlighting existing challenges and providing insights into potential future directions that integrates synthetic processes, novel methods for photoelectric characterization, and an in-depth understanding of the local structure of Nb 2 O 5. This review serves as a valuable resource for researchers in the field, offering a comprehensive overview of the state-of-the-art in Nb 2 O 5 -based heterojunctions for advanced photocatalytic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni 5 P 4 /g-C 3 N 4 S-scheme dual-function heterojunction photocatalyst was prepared. • 25NP/CN junction shows 40.1 mmol g-1h-1H 2 evolution and 94.4 % CBZ removal in a coupled process. • Holes and OH radicals for CBZ degradation and electrons for H 2 generation via e-/H 2 O and 2e-/2H+. • Intermolecular H+ transfer via cyclic intermediate between Ni and degradation products. • Junction works in oxic/anoxic mediums- detailed mechanisms analysed. With a goal of waste-to-energy conversion, herein we report synchronous hydrogen evolution and pollutant degradation via photocatalysis utilizing novel Ni 5 P 4 /g-C 3 N 4 S-scheme (Step scheme) heterojunction. The 25 %Ni 5 P 4 /g-C 3 N 4 (25NP/CN) sample generates 40.1 mmol g-1h-1hydrogen evolution and 94.4 % carbamazepine degradation simultaneously under visible light and anaerobic conditions. Furthermore, the hydrogen evolution with carbamazepine, bisphenol A, sulfamethoxazole and rhodamine B is manifolds higher than in water. From The in-situ XPS results confirm the S-scheme transfer between Ni 5 P 4 and g-C 3 N 4. The presence of Ni0@Ni 5 P 4 where strong covalent interactions between Ni0 and Ni-P single layers on Ni 5 -P 4 not only enhanced the visible absorption, charge transfer but also leads to hydrogen formation by H+ transfer via a cyclic intermediate in a co-ordinate complex of degradation intermediates with Ni. This route is in addition to obvious e-/H+. The CBZ degradation and hydrogen evolution in aerobic/oxic conditions was also studied and 25NP/CN performs well under this atmosphere, inferring that oxidised intermediates act as electron donors and maintains the H 2 evolution in longer run too. The photogenerated holes directly oxidized the pollutant in addition to OH radicals in anoxic medium and separated/accumulated electrons leads to hydrogen evolution. The scavenging experiments reveal that photogenerated holes directly oxidized the pollutant in addition to OH radicals in anoxic medium and separated/accumulated high potential electrons (via S-scheme transfer) leads to hydrogen evolution. The clean energy production and pollutant mineralization are synchronously achieved. Henceforth, a waste-to-energy route is proposed by coupling photocatalytic hydrogen evolution to environmental restoration. [ABSTRACT FROM AUTHOR]

Rationally fabricated Z -scheme hetero-junctions with intimate interfacial contact have proven to accelerate the photocatalytic degradation of noxious pollutants by effectively suppressing the recombination and promoting charges transfer rate. Herein, we report fabrication of reduced graphene oxide (RGO) modified LaTiO 2 N/Bi 2 S 3 heterojunction photocatalyst by sovothermal route. The microstructure analysis, structure determination, electronic and optical analysis of as prepared photocatalysts was done by using multiple techniques. The Z -scheme LaTiO 2 N/Bi 2 S 3 @RGO (LBR) photocatalyst shows remarkable performance for photo-degradation of tetracycline (TC) under visible light. 96.4% TC was eliminated within 90 min under visible light with ~100% removal in 60 min under full spectrum irradiation. In addition the heterojunction shows 80.2% TC removal under natural sunlight irradiation. The TC degradation with LBR heterojunction is ~9 times faster than bare Bi 2 S 3. The Z -scheme transfer follows the route as Bi 2 S 3 → RGO → LaTiO 2 N and provides a swift path for movement of electrons from CB of LaTiO 2 N to VB of Bi 2 S 3. The possible degradation route of TC has also been proposed based on quenching experiments and identification of degradation intermediates by Liquid chromatography-mass spectrometry (LC-MS). The quenching experiments reveal that O 2 – radicals are the main active species involved followed by OH radicals which has been explained by thermodynamic feasibility of their production from the junction arrangement. The mechanism has been explained by Z -scheme transfer by comparing to the conventional type-II junction. The enhancement in photocatalytic activity is primarily attributed to Z-scheme charge transfer between LaTiO 2 N and Bi 2 S 3 facilitated by reduced graphene oxide sheet via strong interfacial contact maintaining high potential for redox conversions. The recycling experiments reveal the stability and reusability of the LBR hybrid photocatalyst with ability to perform under sunlight. The novel nitrides-phosphide based junction with improved properties for visible and solar photocatalytic activity provides future prospects in forming superior hetero-structures for environmental remediation. Unlabelled Image • LaTiO 2 N/Bi 2 S 3 @RGO heterojunction photocatalyst fabrication by simple solvothermal route. • High performance degradation of tetracycline-visible, full spectrum and sunlight • Interfacial charge transfer capacity-internal electric field–higher spectral capture. • Z-scheme and RGO lead to high charge separation, high redox capability, stability. • Thermodynamic feasibility and experimental findings suggest Z-scheme over conventional type-II transfer. [ABSTRACT FROM AUTHOR]

The voluminous anthropogenic activities and non-regulated discharge of emerging pharmaceutical pollutants have led to deterioration of water quality characteristics and shortage of potable water. One of most ubiquitous problems is that the pharmaceutical pollutants are slowly developing resistance in pathogens, which increases the risks manifold. Conventional water treatment methods and technologies have been known to be inadequate for elimination of recalcitrant and emerging pollutants. Advanced oxidation processes have been exploited to the most for mineralizing the pollutants with some limitations especially toxic metal based catalysts and secondary pollution. However Fenton-based systems are considered to be safer as they utilize non-toxic chemicals. Homogeneous Fenton processes suffer from limitations as limited pH operational range, generation of Fe containing sludge etc. have shifted focus to heterogeneous systems. This review focusses on removal of pharmaceutical pollutants by homogeneous and heterogeneous Fenton, electro-Fenton, sono-Fenton, photo-Fenton and photo-electro-Fenton processes using nano-catalysts. Various types of new pharmaceutical pollutants, their emergence, characteristics and toxicity have been discussed to have an insight into quantity and variety. New Fenton-like catalysts have been designed and used for degradation of pollutants and high mineralization is also achieved in a wide pH-range. In addition Fenton catalysts capable of showing high mineralization using solar light have been prepared by various methods with and without iron based materials. In addition in this review we have also focused on complexities related to removal of pharmaceutical effluents and how they are addressed by Fenton systems. The review aims to assist researchers and engineers to gain fundamental understandings and critical view of Fenton process and its optimization processes, and hopefully with the knowledge it could bring new opportunities for the optimization and future development of Fenton process. The key advances in Fenton catalysts are innovations in design of ligands, junction designing for effective radical generation, reaction engineering, hydro-dynamical effects and complete mineralization. The combinations and coupling of biological oxidation, semiconductor photocatalysis with Fenton process for high performance pharmaceutical pollutants removal in pilot-scale experiments have been discussed and evaluated. • Pharmaceutical pollutants as emerging class of toxic pollutants. • Fenton, electro-Fenton, photo-Fenton processes: Safe, Cheap and environmental benign. • Controllable parameters for effective degradation of pharmaceutical pollutants. • Heterogeneous photo-Fenton reaction better than homogenous. • Focus on coupled Fenton and biological oxidation systems. [ABSTRACT FROM AUTHOR]