A systematic review on Nb2O5-based photocatalysts: Crystallography, synthetic methods, design strategies, and photocatalytic mechanisms

Ultra-thin Nb2O5 nanosheets construct 3D cross-linked architecture: Unraveling new coccine degradation pathways and toxicity changes

Photocatalytic technology offers a promising approach to address environmental and health challenges posed by the food colorant new coccine (NC). Nb2O5 is a notable candidate due to its stability and environmental compatibility, but faces limitations such as limited active sites and rapid charge carrier recombination. In the present study, we report a novel Nb2O5 catalyst featuring a three-dimensional (3D) cross-linked architecture constructed from ultra-thin nanosheets, with a catalyst thickness of less than 2 nm. This innovative structure offers an eminent superficial surface area combined with a substantial abundance of active sites, making it an efficient photocatalyst for the degradation of NC. The Nb2O5 3D catalyst demonstrated a remarkable degradation rate of 90.1 % for NC within just 30 min, accompanied by a rate constant of 73.5 × 10-3 min-1. This performance significantly surpasses that of three alternative Nb2O5 catalysts with varying morphologies (nanorods, nanoparticles, and nanospheres), which show rate constants more than seven times lower. Furthermore, we explore the degradation pathways associated with NC and provide a thorough examination of the toxicity changes occurring in its by-products. This work presents a promising framework for the development of advanced catalysts capable of effectively degrading NC, thereby contributing to the advancement of environmentally sustainable practices in the management of food colorants.

Potential of Nb2O5 as a Catalyst in Biodiesel Production: A Study with Different Feedstock

The objective of this study was to evaluate the catalytic performance of commercial Nb2O5, supplied by CBMM, in the production of biodiesel by transesterification and esterification, using different feedstocks (soybean, corn, sunflower, and waste oils) and both methyl and ethyl routes. For this, the catalyst was characterized in terms of its crystal structure by X-ray diffraction (XRD), specific surface area using the Brunauer-Emmett-Teller (BET) technique, thermal stability by thermogravimetric analysis (TGA), morphology by scanning electron microscopy (SEM), acidity by ammonia desorption at programmed temperature (TPD-NH3), and catalytic activity by gas chromatography. The results from the structural analyses indicated that Nb2O5 has a single monoclinic phase and a morphology consisting of irregular agglomerates. The specific surface area was 1.3 m2/g, and its density was 4.639 g/cm3. The thermogravimetric analysis showed that the material has thermal stability, maintaining its structural integrity up to temperatures as high as 1000 °C. The total acidity reached 301 μmol NH3/g, indicating the presence of Brønsted and Lewis acidic sites. In catalytic tests, Nb2O5 showed higher efficiency in the methyl route, achieving an initial conversion of 96.43% in esters with soybean oil, outperforming other feedstocks. However, catalyst reuse over five cycles revealed a progressive decrease in catalytic activity, possibly due to blocking active sites by adsorbed products, as confirmed by FTIR and XRD analyses conducted on the catalyst. Despite decreased activity after the cycles, the catalyst maintained its crystal structure, indicating structural stability. These results demonstrate the potential of Nb2O5 as a heterogeneous catalyst for biodiesel production, particularly with the methyl route and high-quality oils. This study highlights the relevance of Nb2O5 in biodiesel synthesis, contributing to sustainable practices and technological advancement in the renewable energy sector.

Improved hydrogen production performance of an S-scheme Nb2O5/La2O3 photocatalyst

Addressing the intricate challenge of simultaneously improving the separation of photoinduced electron-hole pairs and enhancing redox potentials to produce hydrogen fuel demands the rational design of S-scheme heterojunction photocatalysts. Herein, we used a hydrothermal process to integrate Nb2O5 nanorods and La2O3 nanosheets to design an Nb2O5/La2O3 S-scheme system for photocatalytic hydrogen production under simulated sunlight illumination. Notably, the optimal hydrogen production performance of Nb2O5/La2O3 (the molar ratio of Nb2O5 to La2O3 is 0.4% and denoted as 0.4NbO-LaO) reached 2175 μmol h-1 g-1, which is 14.5 and 15.9 times superior in comparison with those of pure Nb2O5 and La2O3, respectively. In addition, repeated experiments verify the strong stability of the 0.4NbO-LaO photocatalyst. The S-scheme mechanism, verified by the in situ XPS method, plays a crucial role in producing hydrogen with a significantly higher yield than pure Nb2O5 and La2O3. This design approach offers an innovative avenue to widen the scope of S-scheme photocatalysts for solar fuel production.

Construction of the Co3O4/Nb2O5 Composite Catalyst with a Prickly Spherelike Architecture for CO2 Cycloaddition with Styrene Oxide

A high-performance Nb2O5-based catalyst for the cycloaddition of CO2 with SO is designed by properly unifying the concepts of compositional regulation and architectural engineering. The Co3O4/Nb2O5 composite catalyst shows an intriguing prickly spherelike morphology. It exhibits a high styrene carbonate (SC) yield of 94.3% within 4 h (0.0824 mol g-1 h-1) under mild reaction conditions (0.4 MPa of CO2 and a reaction temperature of 90 °C) assisted by tetrabutylammonium bromide (TBAB). The coupling of Co3O4, which chemically interacts with Nb2O5, can effectively modulate the electronic structures of Nb2O5, constructing abundant acid/base sites for effectively activating the reactants and boosting the intrinsic activity. The high activity, cost-effectiveness, and good recyclability make the tailor-made Co3O4/Nb2O5 prickly spheres more appealing for commercial applications. This work offers new insights into designing and constructing well-integrated metal oxide composites for the cycloaddition of CO2 with an epoxide.

NiAlFe LTH /MoS2 p-n junction heterostructure composite as an effective visible-light-driven photocatalyst for enhanced degradation of organic dye under high alkaline conditions

Designing of an effectual heterostructure photocatalyst for catalytic organic pollutant exclusion has been the subject of rigorous research intended to resolve the related environmental aggravation. Fabricating p-n junctions is an effective strategy to promote electron-hole separation of semiconductor photocatalysts as well as enhance the organic toxin degradation performance. In this study, a series of n-type NiAlFe-layered triple hydroxide (LTH) loaded with various ratios of p-type MoS2 was synthesized for forming a heterostructure LTH/MoS2 (LMs) by an in situ hydrothermal strategy. The photocatalysts were characterized by XRD, SEM&EDX, TEM, FT-IR, XPS, as well as UV-vis DRS. The photoactivity of photocatalysts was tested by the degradation of Indigo Carmine (IC) dye. The optimized catalyst (LM1) degrades 100% of indigo dye in high alkaline pH under UV light for 100 min. Besides, the degradation rate of LM1 is 15 times higher than that of pristine NiAlFe-LTH. The enhanced photoactivity is attributed to the synergistic effect between NiAlFe-LTH and MoS2 as well as the p-n junction formation.