Vanadium sulfide sub-microspheres: A new near-infrared-driven photocatalyst

Life cycle sustainability assessment of optimized biodiesel production from used rice bran oil employing waste derived-hydroxyapatite supported vanadium catalyst

The present work encompasses the production of biodiesel from an inexpensive waste, viz., used rice bran oil (URBO) through concurrent esterification and transesterification reactions employing the prepared waste duck bone (WDB)-derived natural hydroxyapatite (NAHAp) supported vanadium impregnated solid catalyst (VNAHAp). The optimal VNAHAp catalyst possessed 92.23 m²/g surface area which was much superior to 61.46 m²/g of the V-catalyst (VCHAp) prepared using commercially available hydroxyapatite (CHAp). The optimal (Box-Behnken design) concurrent trans/esterification reaction conditions for biodiesel (FAME) production from URBO and methanol were 5 wt.% catalyst concentration, 8:1 methanol/URBO mole ratio, and 35 wt% NH₄VO₃ loaded VNAHAp (35VNAHAp) catalyst that resulted in 99.05% FAME yield deploying a low-energy infrared radiator assisted batch reactor (LIRABR) which ensured significantly high FAME yield at milder temperature (60°C) and in shorter reaction time (30 min) compared to a conventionally heated batch reactor. The product biodiesel and its blend with commercial diesel conformed to ASTM D7467-10 specifications. The life cycle assessment (LCA) of the entire process advocated superior sustainability of the biodiesel production using 35VNAHAp catalyst in the LIRABR compared to their conventional counterparts. Valorization of two potential wastes, viz., URBO and WDB, under milder process conditions involving LIRABR and 35VNAHAp resulted in lower environmental impacts, thus rendering a sustainable biodiesel production process towards a greener earth.

Near-Infrared-Responsive Photocatalysts

Broadening the absorption of light to the near-infrared (NIR) region is important in photocatalysis to achieve efficient solar-to-fuel conversion. NIR-responsive photocatalysts that can utilize diffusive solar energy are attractive for alleviating the energy crisis and environmental pollution. Over the past few years, considerable progress on the component and structural design of NIR-responsive photocatalysts have been reported. This study aims to systematically summarize recent progress toward the material design and mechanism optimization of NIR-responsive photocatalysts in this area. Depending on the main strategies for harvesting NIR photons, NIR-responsive photocatalysts can be categorized as direct NIR-light photocatalysts, indirect NIR-light photocatalysts, and photothermal photocatalysts. Furthermore, the construction and application of different NIR-responsive photocatalytic systems are summarized. Conclusions and perspectives are presented to further explore the potential of NIR-responsive photocatalysts in this field.

Near-Infrared-Driven Photocatalysts: Design, Construction, and Applications

Photocatalysts, which utilize solar energy to catalyze the oxidation or reduction half reactions, have attracted tremendous interest due to their great potential in addressing increasingly severe global energy and environmental issues. Solar energy utilization plays an important role in determining photocatalytic efficiencies. In the past few decades, many studies have been done to promote photocatalytic efficiencies via extending the absorption of solar energy into near-infrared (NIR) light. This Review comprehensively summarizes the recent progress in NIR-driven photocatalysts, including the strategies to harvest NIR photons and corresponding photocatalytic applications such as the degradation of organic pollutants, water disinfection, water splitting for H₂ and O₂ evolution, CO₂ reduction, etc. The application of NIR-active photocatalysts employed as electrocatalysts is also presented. The subject matter of this Review is designed to present the relationship between material structure and material optical properties as well as the advantage of material modification in photocatalytic reactions. It paves the way for future material design in solar energy-related fields and other energy conversion and storage fields.

A simple chemical method for the synthesis of Cu2+ engrafted MgAl2O4 nanoparticles: Efficient fluoride adsorbents, photocatalyst and latent fingerprint detection

An adaptable, energy efficient chemical process is employed to synthesize Cu²⁺ engrafted MgAl₂O₄ nanoparticles (Mg_1-xCu_xAl₂O₄, x=0, 0.1, 0.3, 0.5 abbreviated as MCA0, MCA1, MCA3, and MCA5 respectively), using chelating ligand and the calcination temperature was determined by the thermogravimetric analysis of the precursor mass. They acted as good fluoride adsorbent in the presence of co-ions, different pH (2-11) via chemisorption revealed from Fourier-transform infrared spectroscopy (FTIR) and photodegraded Methylene Blue (MB). The satisfactory results were for MCA1 (specific surface area 25.05m²/g) with 97% fluoride removal at pH7.0 for the 10mg/L initial fluoride concentration for 1.5g/L adsorbent dose with 45min contact time obeying the Langmuir isotherm model with negative thermodynamic parameters and 4mmol of MCA3 with 98.51% photodegradation for 10^-5mol/LMB solution obeying pseudo-second-order and pseudo-first-order kinetics respectively. The proposed photodegradation mechanism of MB was established by the FTIR and high-performance liquid chromatography (HPLC) analysis. The nanoparticles are cubic, estimated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The band gap energies, grain size, and the effective working pH were estimated by diffuse reflectance spectra (DRS), scanning electron microscope (SEM), and zero-point potential analysis respectively. A soil candle with MCA1 also fabricated for the household purpose and tested with some fluorinated field samples. The MCA3 was able to enhance the latent fingerprint on smooth surfaces.

Challenges and implication of full solar spectrum-driven photocatalyst

Conventional metal oxide and its composites embrace the long-standing problem of using the combined visible and near-infrared (NIR) light. Doping with suitable impurities of metal, nonmetal, or its combinations for visible light enhancement is very well studied. However, the quantum efficiency of these photocatalysts does not produce an exciting appearance toward visible and NIR light when irradiated through either artificial or natural light. Furthermore, owing to the limited availability of solar light, challenges arise from the implication of these developed nano-photocatalysts. Therefore, the hybridized concept was developed for the effective use of either full or partial solar spectrum, even functioning in dark conditions. The present review focuses on the challenges of hybridized photocatalysts in storing and discharging the harvested photons obtained from the solar spectrum. The review vividly emphasizes the evolution of light-driven nanomaterials since its innovation and significant breakthroughs in brief, while a detailed presentation of the implications of hybrid photocatalysts for full solar applications, including the mechanistic features, charging-discharging characteristics, work function, charge carrier mobility, and interactions, follows. The article also delivers the substantial contribution of these materials in regard to energy and environmental application.

Full-Spectrum Photocatalytic Activity of ZnO/CuO/ZnFe2O4 Nanocomposite as a PhotoFenton-Like Catalyst

Deriving photocatalysts by the calcination of hydrotalcite-like compounds has attracted growing interest for extending their photocatalytic activity to the visible and even near-infrared (NIR) light regions. Herein, we describe the acquisition of a ZnO/CuO/ZnFe2O4 nanocomposite with good photoFenton-like catalytic activity under UV, visible and near-infrared (NIR) light irradiation by optimizing the calcination temperature of the coprecipitation product of Zn2+, Cu2+ and Fe3+. The ZnO/CuO/ZnFe2O4 nanocomposite is composed of symbiotic crystals of ZnO, CuO and ZnFe2O4, which enable the nanocomposite to show absorption in the UV, visible and NIR light regions and to produce a transient photocurrent in the presence of H2O2 under NIR irradiation. The full-spectrum photoFenton-like catalyst shows improved performance for the degradation of methyl orange with an increasing amount of H2O2 and is very stable in the recycling process. We believe that the ZnO/CuO/ZnFe2O4 nanocomposite is a promising full-spectrum photoFenton-like catalyst for the degradation of organic pollutants.

Visible-to-NIR Photon Harvesting: Progressive Engineering of Catalysts for Solar-Powered Environmental Purification and Fuel Production

Utilization of diffusive solar energy through photocatalytic processes for environmental purification and fuel production has long been pursued. However, efficient capture of visible-near-infrared (NIR) photons, especially for those with wavelengths longer than 600 nm, is a demanding quest in photocatalysis owing to their relatively low energy. In recent years, benefiting from the advances in photoactive material design, photocatalytic reaction system optimization, and new emerging mechanisms for long-wavelength photon activation, increasing numbers of studies on the harnessing of visible-NIR light for solar-to-chemical energy conversion have been reported. Here, the aim is to comprehensively summarize the progress in this area. The main strategies of the long-wavelength visible-NIR photon capture and the explicitly engineered material systems, i.e., narrow optical gap, photosensitizers, upconversion, and photothermal materials, are elaborated. In addition, the advances in long-wavelength light-driven photo- and photothermal-catalytic environmental remediation and fuel production are discussed. It is anticipated that this review presents the forefront achievements in visible-NIR photon capture and at the same time promotes the development of novel visible-NIR photon harnessing catalysts toward efficient solar energy utilization.

VS2: an efficient catalyst for an electrochemical hydrogen evolution reaction in an acidic medium

A single step scalable synthesis for vanadium disulphide (VS₂) was developed and the resulting material shows a better electrocatalytic performance in terms of a low onset potential (15 mV), a lower Tafel slope (36 mV dec⁻¹) and needs only 41 mV to deliver a state-of-the-art current density of 10 mA cm⁻².