The increasing release of nitrogen oxides (NOx) is a serious risk to human and environmental health, and thus, the stringent scrutiny and application of clean and highly efficient NOx remediation technologies are required. To support this, photocatalytic remediation has become a promising method, and oxygen vacancies (OVs) have become crucial in the activity of the immobilised bismuth catalysts. This review offers an extensive summary of the new advances achieved in the engineering of OVs into complex Bi-based photocatalysts to deliver highly efficient NOx reduction. The major approaches that are discussed in terms of their ability to create controlled OV populations are thermal treatment, chemical reduction, atomic-scale accuracy, and radiation. The relationships between structure and properties of OV incorporation, synergistic metal or elemental doping, light absorption promotion, charge separation enhancement, and surface redox acceleration and morphological changes, including heterojunction construction, plasmonic nanoparticle loading, and elemental doping, are explained. Spectroscopic and computational analyses explain the mechanisms through which NOx undergoes activation and transformation into nitrates by the mechanisms of adsorption, activation, and transformation of NOx. Lastly, the review determines key challenges, viable aspects, and future perspectives of translating these sophisticated photocatalysts to scalability, functionality, and real-world application of removing NOx in the world.

Harnessing solar energy through photocatalysis offers a promising pathway for sustainable energy conversion and environmental remediation. Central to this progress is the development of efficient photocatalysts capable of activating inert N2 molecules under mild conditions. Recently, dual-atom catalysts (DACs) have emerged as a transformative class of materials that bridge the gap between single-atom and nanoparticle catalysts by providing synergistic bimetallic active sites with maximized atomic utilization. This review concisely summarizes recent advances in the coordination microenvironment, structural design, and catalytic mechanisms of transition metal-based dual-atom catalysts (TM-DACs) for photocatalytic N2 conversion. Particular emphasis is placed on how electronic coupling, metal–metal interactions, and coordination configuration of TM-DACs govern charge transfer dynamics, adsorption behavior, and reaction kinetics during the N2 reduction process. Synthesis strategies, characterization techniques, and mechanistic pathways of TM-DACs are comprehensively discussed, highlighting their advantages over single-atom systems. Furthermore, emerging trends and challenges in developing noble metal-free, earth-abundant DACs for efficient NH3 production are outlined. This review aims to provide fundamental insights and design principles for constructing next-generation TM-DACs for highly efficient and sustainable photocatalytic applications. Schematic of the coordination microenvironment and dual-metal synergy in transition metal-based dual-atom catalysts (TM-DACs) for photocatalytic N2 fixation. Design strategies, active site interactions, charge transfer pathways, and reaction mechanisms are highlighted to guide the development of effective and sustainable photocatalysts for NH3 production.

The present work evaluated the efficacy of a Sono-Photo-Fenton technique using ternary vanadate InVO4/BiVO4/ FeVO4 for the degradation of tetracycline (TCL), a persistent pharmaceutical pollutant. A comprehensive evaluation of the ultrasound (US), Visible light (Vis-L), and advanced oxidation processes (AOPs) along with H2O2 and InVO4/BiVO4/FeVO4 photocatalysts to elucidate synergistic effects and underlying mechanisms. The photocatalyst was prepared and characterized through several analytical methods, such as FESEM and TEM, and XRD to investigate their morphology and crystal size, revealing an average size of 271.9 nm, which confirms the uniformity of the synthesized particles. The electronic structure and band alignments of the InVO4/BiVO4/FeVO4 photocatalyst were elucidated through DFT simulations, Tauc-plot, and Mott-Schottky (MS) analysis. Further, Electron spin resonance (ESR) analysis provides insights into the charge migration route during the proposed dual s-scheme mechanism. Significant degradation efficiency of 98.28 % was achieved under optimized conditions: H2O2 + InVO4/BiVO4/FeVO4 dosage of 80 mg, ultrasonic frequency of 20 kHz, Vis-L power of 500 W, and a reaction time of 120 min. Degradation kinetics confirmed a pseudo-first-order reaction with rate constant of 0.036 min-1, and the TCL degradation pathway was elucidated by LC-MS analysis, confirming the breakdown of TCL into CO2, H2O, and other inorganic substances. This study highlights the potential of energy-driven irradiation using three techniques US + Vis-L + H2O2-InVO4/BiVO4/FeVO4 i.e., Sono-Photo-Fenton process using ternary vanadate as a promising strategy for the treatment of pharmaceutical contaminants in wastewater, offering insights into the mechanisms of enhanced degradation.

The rational construction of a photocatalytic system that maximizes sunlight harnessing and facilitates its redox abilities is still an intriguing research domain in photocatalysis technology. The present study reports synthesising a novel S-scheme nanocomposite system combining CeO2 and oxygen vacancies (OVs) modified self-doped Ti3+-doped TiO2. A unique approach of incorporating active site engineering via OVs generation in self-doped Ti3 +-TiO2 and Ce3 + /Ce4+ valency exchange in CeO2 has synergistically endorsed the photoredox potential in the resulting heterostructure system. Typically, the OVs in Ti3 +-TiO2 serve as electron-rich centres, stimulating charge isolation and effective visible light absorption, while the Ce3 + /Ce4+ valency exchange dynamics in CeO2 facilitate effective electron shuttling and redox capabilities. This synergistic arrangement not only fosters interfacial charge transference but also expedites the overall redox potential, rendering superior catalytic activity in both oxidation and reduction reactions. As a result, the mid-state energy level and dual redox-active sites equipped Ti3 +-TiO2/CeO2 system exhibit 84 % 4-nitrophenol photo-reduction to 4-aminophenol and 90.6 % photo-oxidative degradation of Sunset Yellow dye. Density Functional Theory (DFT) calculations and Bader charge analysis helped in identifying the exposed attacking sites that enabled selective photocatalytic interactions. Moreover, chromatography analyses (HPLC and LCMS-MS) further aided in understanding the reductive and oxidative mechanisms, respectively. The nanocomposite photocatalyst showed excellent stability under the experimental conditions and exhibited up to four cycles with no significant loss in efficacy. This study demonstrates the dual functionality of the S-scheme nanocomposites aimed at designing multifunctional photocatalytic materials to address critical environmental challenges. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

In the field of photocatalysis, precise defect engineering has emerged as a controlling strategy to improve the performance of semiconductor materials. Among them, bismuth oxychloride (BiOCl) stands out due to its different layered structure and built-in electric fields, which together facilitate efficient charge separation. This review provides a comprehensive overview of recent advancements in tailoring intrinsic defects, particularly oxygen vacancies, chloride vacancies, and bismuth-related defects, in BiOCl. Advanced characterization techniques such as density functional theory (DFT), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are discussed for their role in identifying and quantifying these defect states. The weak interlayer interactions and distinctive stacking arrangement in BiOCl offer a flexible platform for defect modulation, enabling precise control over surface reactivity and catalytic selectivity. Particular emphasis is placed on metal and non-metal doping strategies that modify the band structure and enhance charge carrier dynamics. The construction of heterostructures, including type-II, Z-scheme, and Sscheme configurations, is also explored to further improve redox capability. BiOCl-based materials demonstrate outstanding photocatalytic activity in H2 production, CO2 reduction, and degradation of organic pollutants. This review highlights the strategic importance of defect engineering in optimizing BiOCl photocatalysts by elucidating the interplay between defect types and photocatalytic mechanisms. It offers valuable guidance for designing next-generation photocatalytic materials with high efficiency and sustainability to address global environmental and energy challenges.

H2 and O2 generation are vital in pursuing sustainable energy, aligning with Sustainable Development Goal 7. 2D photocatalysts are promising due to their unique structure and high surface-to-volume ratio, enhancing catalytic efficiency. Carbon-based materials stand out for their excellent it-it conjugation, strong light absorption, and chemical versatility. Despite limitations, they hinder their broad-scale use, such as limited charge carrier kinetics, restricted light absorption, suboptimal quantum efficiency, graphene's chemical inertness, and agglomeration issues. This review paper mainly highlights the role of metal-free defects in 2D nanocarbons in revolutionizing solar-to-energy conservation. These metal-free photocatalysts are promising candidates for sustainable catalytic processes owing to the defect sites in the carbon matrix, categorized as metal-free point defects and volume defects. The main emphasis is on understanding how point and volume defects improve the overall photocatalytic efficiency. Point defects, including carbon and nitrogen, usually disrupt the electron distribution in the lattice, and volume defects, involving lattice distortions, edge defects, Stone-Wales defects, and pits/voids, generate abundant active sites. This integrated approach, combining defect engineering, material diversity, and practical applications, positions the review as a significant and innovative contribution to the field. Leveraging the properties of carbon-based 2D materials and addressing various challenges through defect engineering can lead to the development of highly effective and sustainable photocatalysts, advancing renewable energy efforts and contributing to global sustainability.

Every year, a large number of plastic products are used extensively and discarded worldwide, causing severe plastic pollution that contaminates the soil, air, and water supplies. While solar energy can help in the sustainable degradation of plastics, the process takes time and releases harmful chemicals that contaminate the food and water cycles. This review examines existing conventional methods and emerging processes for solar-driven catalytic plastic degradation. Conventional methods, such as pyrolysis, catalytic cracking, hydrogenolysis, and electrocatalysis, are discussed, focusing on the requirement for a more sustainable approach. In particular, this review highlights how the catalytic potential can be enhanced by activating chemical bonds to yield value-added products by photocatalytic upcycling under moderate circumstances. Photocatalytic upcycling, as a sustainable approach, has been explored for hydrogen production and the production of value-added chemicals using the waste plastic substrate, signifying “treasure from trash”. The key obstacles to the uptake and expansion of these technologies are identified, along with recommendations for future research directions to improve the effectiveness of upcycling techniques.

To date, the global demand for clean water and environmentally detrimental human activities are among the most significant challenges humans face. Therefore, an urgent need is to innovate and implement more effective, sustainable solutions to protect the environment and preserve our vital water resources. In particular, this study successfully developed a new and suitable nanocomposite catalyst from waste polyethylene terephthalate (PET) plastics-derived activated carbon (P-AC) and applied it for the enhanced photo-degradation of tetracycline (TCHCl). Based on the characterizations and density functional theory (DFT) calculations, we suggest that the synergistic effect of adsorption and photocatalysis by synthesizing oxygen vacancy-rich Bi4O5Br2 (BOB) and Co3(PO4)2 (COP) immobilized on P-AC play a critical role in enhancing effectively further the degradation efficiency. Interestingly, the proposed S-scheme charge transfer mechanism demonstrated an impressive TC-HCl degradation efficiency of 90.7 % within 90 min under light irradiation. It notes that the degradation mechanism involved the pre-adsorption of TC-HCl onto the surface of functional group-rich activated carbon, which assisted in hastening the attack of O2 center dot- and h+. Nine primary intermediates were identified, framing three degradation pathways for TC-HCl as per liquid chromatography - mass spectrometry (LC-MS). Lastly, results of consecutive quadruplicate degradation experiments advocated the stability and reusability of the nanocomposite, highlighting the potential of upcycling plastic waste into valuable photocatalytic materials support, offering an effective and environmentally friendly solution for removing priority pollutants from water.

Photocatalytic Graphitic carbon nitride (g-C3N4) is an extensively studied metal-free catalytic material due to its visible-light activity, thermal stability, and eco-friendly nature. Though, its photocatalytic efficacy is controlled by poor charge isolation, small surface area, as well as insufficient oxidation and reduction potential. To overcome these associated drawbacks, hybridization with molecular catalysts, for example, phthalocyanines (Pc), tetraphenyl porphyrins (TPP), and other conjugated organic complexes has arisen as a significant strategy. This review paper provides a comprehensive overview of molecular catalyst/g-C3N4 hybrid catalytic systems, focusing on their fabrication, interfacial chemistry, and structural alterations. Modification strategies such as elemental doping, defect engineering, and the formation of heterojunctions, mainly S-scheme heterojunctions, are critically deliberated. These methods aim to optimize the charge isolation pathways as well as redox properties vital for photocatalytic efficiency. Hybrid systems based on molecular catalysts and g-C3N4 demonstrate remarkable efficacy in H2 generation, CO2 photoreduction, and organic contaminant degradation. S-scheme heterojunctions, in particular, enable effective spatial charge isolation while retaining strong redox efficacy. This paper highlights the significance of hybrid molecular catalyst engineering as a powerful strategy to reveal the potential of photocatalytic g-C3N4-based catalysts for supportable energy and environmental applications.

Nitrogen-doped magnetic biochar (N-doped magnetic BC) has garnered significant attention as a multifunctional material for the remediation of antibiotic-contaminated water, owing to its synergistic adsorption and catalytic degradation capabilities. This review critically evaluates the transformative role of pretreatment strategies on the physicochemical attributes of biochar, focusing on nitrogen doping and chemical activation. These methodologies are complemented by post-treatment processes designed to impart synergistically optimized magnetic properties to the biochar matrix. Such modifications are pivotal in fine-tuning the material’s characteristics, including surface area, pore architecture, and active site configuration, thereby enhancing its adsorption efficiency and catalytic performance. Advanced characterization techniques, such as electron microscopy, X-ray diffraction, and various spectroscopic modalities, provide comprehensive insights into the structural, surface, and magnetic properties of nitrogen-doped magnetic BC. The adsorption mechanisms are predominantly governed by π-π interactions, hydrogen bonding, and electrostatic forces, with nitrogen doping and magnetic functionalization significantly amplifying the material’s selectivity and adsorption capacity. Furthermore, the catalytic degradation of antibiotics occurs via both radical and non-radical pathways, underscoring the dual functionality of the material. Notably, N-doped magnetic BC demonstrates excellent recyclability, maintaining high efficiency across multiple adsorption–desorption cycles. This highlights its potential for sustainable application. Future research directions proposed in this study emphasize advancing the eco-compatibility and scalability of N-doped magnetic BC. Computational modelling is suggested to predict and optimize the material’s physicochemical properties, alongside the development of large-scale, environmentally benign synthesis techniques. These advancements aim to position N-doped magnetic BC as a cornerstone material in wastewater treatment systems.

The study presents the fabrication and superior photoactivity of a ternary g-C3N4/FeVO4/AgBr heterojunction nanocomposite, synthesized via a chemical precipitation method for effective degradation of tetracycline (TC) and Victoria Blue (VB) dye under light illumination. The morphology and the crystal size of the synthesized nanocomposite were characterized by using FESEM and XRD and the calculated grain size (100.39 nm) is larger than the crystal size (48.14 nm) indicating strong interparticle bonding. The heterojunction design leverages dual S-scheme interfacial charge transfer, reducing electron-hole recombination as confirmed by optoelectronic and electrochemical techniques. The composite demonstrated superior performance, achieving 82.15% degradation of TC and 97.25% degradation of VB. The study highlights density functional theory (DFT) simulations and Mott-Schottky (MS) analysis, providing insight into the electronic structure, distribution of charge, and band alignments of the g-C3N4/FeVO4/AgBr nanocomposite. Electron spin resonance and radical scavenging experiments revealed holes and superoxide radicals as the primary species driving the degradation process. Furthermore, LC-MS analysis provided insights into the degradation pathways, confirming the conversion of TC and VB into non-toxic byproducts. The photocatalytic stability was confirmed through five consecutive cycles with minimal disruption in both performance and morphology, demonstrating its potential for wastewater treatment applications. Consequently, this study illustrates how the collaborative interplay of dual S-scheme charge migration and silver plasmonic effects enhances the efficiency of the g-C3N4/FeVO4/AgBr nanocomposite, offering a novel and highly effective solution for the degradation of complex pollutants in environmental remediation.

The survival of humanity is severely threatened by the massive accumulation of waste in the ecosystem. One plausible solution for the management and upcycling of waste is conversing waste at the molecular level and deriving carbon-based nanomaterial. The field of carbon nanomaterials with distinctive properties, such as exceptionally large surface areas, good thermal and chemical stability, and improved propagation of charge carriers, remains a significant area of research. The study demonstrates recent developments in high-value carbon-based photocatalysts synthesis from various waste precursors, including zoonotic, phytogenic, polyolefinic, electronic, and biomedical, highlighting the progression as photocatalysts and adsorbents for wastewater treatment and water splitting applications. This review highpoints the benefits of using waste as a precursor to support sustainability and circular economy and the risks associated with their use. Finally, we support that a sustainable society will eventually be realized by exploring present obstacles and potential steps for creating superior carbon-based nanomaterials in the future.

Background: Rapid industrialization has triggered the proliferation of dyes and antibiotics in the water system in recent decades. Due to advantages like low cost, high catalytic efficiency, and the ability to exist in multiple valences, MnO2 as a photocatalyst has attracted more and more attention. Methods: This review covers recent progress on MnO2-based composites for photocatalytic properties obtained via the Z-scheme charge carrier mechanism. Firstly, the electronic, photoelectric, and crystallographic properties of MnO2 are highlighted, and the fabrication of heterojunctions by suitable band alignments following the Zscheme electron transfer pathway. This article presents recent advances in MnO2-based nanomaterials, focusing on improving photocatalytic activity via the Z-scheme mechanism. Then a detailed discussion on various electron transfer pathways in MnO2-based composites offered a broader view by providing several characterization techniques to testify to the route of the Z-scheme mechanism. Significant Findings: This review also provided a systematic summary of their applications in environmental (dye, antibiotics degradation) and energy (water splitting, CO2 reduction) applications. Although many efforts have been made, significant improvements are still required for photocatalysis. This work presents future perspectives for improving the efficacy of photocatalysts, followed by a conclusion.

To date, the prevalence of commonly used plastics like Polyethylene terephthalate (PET), polylactic acid (PLA), and polybutylene terephthalate (PBT) extends across diverse industries, from textiles to beverage bottles and daily packaging applications. Originally designed for up to 50 years of durable shelf life, these plastics face accelerated disposal challenges due to the pervasive "throw-away" culture. The rapid expansion of single-use plastic manufacturing, notably PET, has led to an astonishing global output of one million tons of plastic each year, highlighting the urgent requirement for efficient solutions in managing plastic waste. Carbon-based nanomaterials derived from PET are synthesized using chemical reactions in solution or high-temperature environments. This review discusses molten salt, hydrothermal, and one-step solvent-based synthesis techniques. We investigate advances in converting PET plastic into nanostructured materials, revealing their potential for energy storage, adsorption, supercapacitors, and sensors. As we navigate the challenges of plastic waste, this review scrutinizes the environmental impact by bridging the gap between plastic pollution and the utilization of upcycled nanomaterials of these pioneering methods, offering insights into their sustainability.

The enhanced environmental contamination of heavy metals has inclined researchers towards enhancing adsorbents. In this regard, Polythiophene (PTh)-based adsorbents have been noticed because of their conjugated polymer structure that makes them have effective delocalized π-system and sulfur-substituted thiophene rings for the adsorption of the heavy metal ions. PTh and its composites have been explored as effective adsorbents to capture heavy metal ions from wastewater because of their high conductivity, chemical stability, and modification ability. These materials can be functionalized with different chemical moieties to improve their adsorption capacities, selectivity, and reusability, making them an ideal candidate for sustainable water treatment technologies. An overview of various adsorbent heavy metal ion removal methods followed by the in-depth analysis of PTh structure, properties, and fabrication techniques. The review highlights the substantial improvement in adsorption capacity and selectivity achieved through modifications enhancing the adsorbent ability to form strong coordination bonds with metal ions. Furthermore, this comprehensive review delves into kinetic and mechanistic insights wherein chemical adsorption is identified as the predominant mechanism for heavy metal capture. The high regeneration ability of modified PTh is also explored, suggesting its potential as a sustainable and efficient solution for large-scale environmental remediation. Despite the effectiveness and recyclability of PTh-based adsorbents, challenges such as economic viability and large-scale application costs of adsorbents are highlighted.

Plasmonic-based semiconductors are compelling contenders of current research endeavors to drive chemical reactions via plasmonic and phononic light-matter interactions. Among various plasmonic metals, Ni as a non-precious metal has been extensively studied due to its ability to participate in interband excitation and comparable metal-hydrogen binding energy to that of noble metals including Pt and Ag. The phenomenally high charge-carrier density in photoexcited Ni-based plasmonic nanomaterials offers photochemical conversion of high-energy chemical bonds accompanied by thermal effect. Since the research on the plasmonic activity of the non-precious metal is still emerging, no comprehensive review has addressed the significance of Ni as a plasmonic photocatalyst to the best of our knowledge. This review article sums up the recent progress in the field of plasmonic photocatalysis focusing on Ni-based photocatalysts. The basic principles of the plasmonic effect have been presented, along with an explanation of why Ni may be a viable option. Ni has been investigated for use as a co-catalyst and plasmonic photocatalyst in composite photocatalysis to achieve an accelerated process. After the energy transfer mechanism has been assessed, the review covers the state-of-the-art of two significant effects—plasmon energy transfer and the localized heating effect that are responsible for increased efficiency in energy production. In conclusion, we have included a synopsis of the assessment and emphasized the problems that must be resolved before the technology can be made available for purchase. In a nutshell, the chemistry of plasmonic photocatalysis is promising; but acquiring a detailed mechanism of charge transfer and utilization of charge carriers is still a roadblock in apprehending the full potential of plasmonic photocatalysis. Therefore, this study aims to motivate the scientific community to envision impactful work in the creation of next-generation plasmonic photocatalysts.

Architecting a desirable and highly efficient nanocomposite for applications like adsorption, catalysis, etc. has always been a challenge. Metal Organic Framework (MOF)-based hierarchical composite has perceived popularity as an advanced adsorbent and catalyst. Hierarchically structured MOF material can be modulated to allow the surface interaction (external or internal) of MOF with the molecules of interest. They are well endowed with tunable functionality, high porosity, and increased surface area epitomizing mass transfer and mechanical stability of the fabricated nanostructure. Additionally, the anticipated optimization of nanocomposite can only be acquired by a thorough understanding of the synthesis techniques. This review starts with a brief introduction to MOF and the requirement for advanced nanocomposites after the setback faced by conventional MOF structures. Further, we discussed the background of MOF-based hierarchical composites followed by synthetic techniques including chemical and thermal treatment. It is important to rationally validate the successful nanocomposite fabrication by characterization techniques, an overview of challenges, and future perspectives associated with MOF-based hierarchically structured nanocomposite.

The rising energy conflicts and environmental pollution are calling for the rapid development of advanced techniques such as photoelectrocatalysis to transform waste into energy and to clean contaminated media. Here we review photoelectrocatalysis for removing wastewater contaminants and recovering energy such as electricity and hydrogen (H-2), with focus on the basics of photoelectrocatalysis, charge kinetics, selecting a photoelectrode, and performance. Modification strategies such as heterostructure formation and doping are discussed. We present applications such a hydrogen production coupled with wastewater treatment, carbon dioxide reduction coupled with pollutant degradation, energy production coupled with wastewater treatment, and microbial fuel cells for electricity generation and pollutant degradation.

Effective degradation of low-concentration pollutants is a critical challenge during the water purification process. The use of different chemicals can leave residue in samples that can impose potential ecotoxicological and adverse impacts on human health. Presently, Magnetic molecularly imprinted polymers (M−MIPs) have attracted much attention as the research material comprises a non-magnetic polymer and magnetic material for selective binding for target molecule and recoverability of catalyst via magnetism, respectively. This review explains the synergistic effect of adsorption with photocatalysis to understand their recognition mechanism and the possible interaction between the target molecule and MIPs. Then their common imprinting polymerization processes i.e., free radical polymerization and non-free radical polymerization are briefly discussed with their respective advantages and disadvantages. In addition, this review highlights the photocatalytic degradation mechanism of photocatalyst cum adsorbent is critically discussed by comparing it with non-imprinted polymers. Finally, the applications of M−MIPs in the removal or degradation of refractory pollutants, sensing, and recognition have also been delineated. This paper summarises progressive future challenges of the technology that need to be exploited for the preparation of the targeted catalyst