Defect and Heterostructure engineering assisted S-scheme Nb2O5 nanosystems-based solutions for environmental pollution and energy conversion

This review explores the crystallographic versatility of niobium pentoxide (Nb2O5) at the nanoscale, showcasing enhanced catalytic efficiency for cutting-edge sustainable energy and environmental applications. The synthesis strategies explored encompass defect engineering, doping engineering, s-scheme formation, and heterojunction engineering to fine-tune the physicochemical attributes of diverse dimensional (0-D, 1-D, 2-D, and 3-D) Nb2O5 nanosystems as per targeted application. In addressing escalating environmental challenges, Nb2O5 emerges as a semiconductor photocatalyst with transformative potential, spanning applications from dye degradation to antibiotic and metal removal. Beyond its environmental impact, Nb2O5 is pivotal in sustainable energy applications, specifically in carbon dioxide and hydrogen conversion. However, challenges such as limited light absorption efficiency and scalability in production methods prompt the need for targeted research endeavors. The review details the state-of-the-art Nb2O5 nanosystems engineering, tuning their physicochemical properties employing material engineering, and their high catalytic performance in environment remediation and energy generation. It outlines challenges, potential mitigation strategies, and prospects, urging for developing greener synthesis routes, advanced charge transfer techniques, targeted optimization for specific pollutants, and application for micro/nano plastics photocatalytic reduction. As researchers and environmental stewards collaborate, Nb2O5 stands poised at the intersection of environmental remediation, energy harvesting, and nanomaterial advancements, offering a beacon of progress toward a cleaner, more sustainable future.

Investigation of Fe-Doped Graphitic Carbon Nitride-Silver Tungstate as a Ternary Visible Light Active Photocatalyst

The rapid population growth and economic development have largely contributed to environmental pollution. Various advanced oxidation processes have been used as the most viable solution for the reduction of recalcitrant pollutants and wastewater treatment. Heterogeneous photocatalysis is one of the broadly used technologies for wastewater treatment among all advanced oxidation processes. Graphitic carbon nitride alone or in combination with various other semiconductor metal oxide materials acts as a competent visible light active photocatalyst for the removal of recalcitrant organic pollutants from wastewater. Rational designing of an environment-friendly photocatalyst through a facile synthetic approach encounters various challenges in photocatalytic technologies dealing with semiconductor metal oxides. Doping in g-C3N4 and subsequent coupling with metal oxides have shown remarkable enhancement in the photodegradation activity of g-C3N4-based nanocomposites owing to the modulation in g-C3N4 bandgap structuring and surface area. In the current study, a novel ternary Fe-doped g-C3N4/Ag2WO4 visible light active photocatalyst was fabricated through an ultrasonic-assisted facile hydrothermal method. Characterization analysis included SEM analysis, FTIR, XRD, XPS, and UV-Visible techniques to elucidate the morphology and chemical structuring of the as-prepared heterostructure. The bandgap energies were assessed using the Tauc plot. The ternary nanocomposite (Fe-CN-AW) showed increased photodegradation efficiency (97%) within 120 minutes, at optimal conditions of pH = 8, catalyst dose = 50 mg/100 ml, an initial RhB concentration of 10 ppm, and oxidant dose 5 mM under sunlight irradiation. The enhanced photodegradation of rhodamine B dye by ternary Fe-CN-AW was credited to multielectron transfer pathways due to insertion of a Fe dopant in graphitic carbon nitride and subsequent coupling with silver tungstate. The data were statistically assessed by the response surface methodology.

Facile Synthesis of Copper Oxide-Cobalt Oxide/Nitrogen-Doped Carbon (Cu2O-Co3O4/CN) Composite for Efficient Water Splitting

Herein, we report a copper oxide-cobalt oxide/nitrogen-doped carbon hybrid (Cu2O-Co3O4/CN) composite for electrochemical water splitting. Cu2O-Co3O4/CN is synthesized by an easy two-step reaction of melamine with Cu2O-Co3O4/CN composite. The designed composite is aimed to solve energy challenges by producing hydrogen and oxygen via electrochemical catalysis. The proposed composite offers some unique advantages in water splitting. Carbon imparts superior conductivity, while the water oxidation abilities of Cu2O and Co3O4 are considered to constitute a catalyst. The synthesized composite (Cu2O-Co3O4/CN) is characterized by SEM, EDS, FTIR, TEM, and AFM in terms of the size, morphology, shape, and elemental composition of the catalyst. The designed catalyst’s electrochemical performance is evaluated via linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The Cu2O-Co3O4/CN composite shows significant electrocatalytic activity, which is further improved by introducing nitrogen doped carbon (current density 10 mA cm−2, onset potential 91 mV, and overpotential 396 mV).

Nb2O5-Based Photocatalysts

Photocatalysis is one potential solution to the energy and environmental crisis and greatly relies on the development of the catalysts. Niobium pentoxide (Nb2O5), a typically nontoxic metal oxide, is eco-friendly and exhibits strong oxidation ability, and has attracted considerable attention from researchers. Furthermore, unique Lewis acid sites (LASs) and Brønsted acid sites (BASs) are observed on Nb2O5 prepared by different methods. Herein, the recent advances in the synthesis and application of Nb2O5-based photocatalysts, including the pure Nb2O5, doped Nb2O5, metal species supported on Nb2O5, and other composited Nb2O5 catalysts, are summarized. An overview is provided for the role of size and crystalline phase, unsaturated Nb sites and oxygen vacancies, LASs and BASs, dopants and surface metal species, and heterojunction structure on the Nb2O5-based catalysts in photocatalysis. Finally, the challenges are also presented, which are possibly overcome by integrating the synthetic methodology, developing novel photoelectric characterization techniques, and a profound understanding of the local structure of Nb2O5.

The improved photocatalytic activity of highly expanded MoS2 under visible light emitting diodes

Photocatalytic degradation is a promising method to remove organic pollutants from water. Photocatalysts based on two-dimensional (2D) transition metal dichalcogenides (TMDs) such as MoS2 nanomaterials have gained tremendous popularity. This is due to their narrow band gap and high visible light absorption. Herein, a MoS2 photocatalyst with highly expanded interlayer spaces of 1.51 nm was synthesized in the presence of Pluronic F-127 as a template by a facile one-pot hydrothermal method. This expanded MoS2 (MF-1) managed to photodegrade 98% (2.62 × 10-2 min-1) of methylene blue (MB) dye under irradiation of 1 W visible light-emitting diode (LED) white light. The dominant performance of MF-1 is attributed to the highly expanded interlayer spacing, which exposed more active edge sites. Moreover, the formation of surface defects such as surface cracks and sulfur vacancies (Sv) facilitates the adsorption capacity and in situ generation of reactive oxygen species (ROS). The dominant ROS responsible for the photodegradation of MB is superoxide radical (˙O2 -). The photocatalyst shows good recyclability without deterioration even after five consecutive cycles.