In optoelectronic devices, transparent, highly electrically conductive bulk glass is expected to play a role comparable to that of thin films. In this context, transparent stand-alone glass can function as a light waveguide and transparent electrode without a substrate, making it suitable for devices that rapidly and seamlessly convert light signals into electrical signals. We report that non-toxic, binary tungsten phosphate glass containing-80 mol% WO3 exhibits a degenerate n-type conductivity of-101 S/cm at room temperature when subjected to strong reduction heat treatment during the melting process. High n-type electrical conductivity is achieved through the formation of oxygen deficiencies and the precipitation of WO3 nanocrystals in the glass, as revealed by high-resolution transmission electron microscopy. X-ray photoemission spectroscopy reveals the presence of blue coloring, attributed to charge transfer between W6+ and W5+, with a W5+/W6+ fraction of-10 %. Continuous-wave electron paramagnetic resonance measurements reveal strong magnetic interactions within the W5+ cluster in the high-conductivity sample.

Ammonia is a cornerstone of fertilizers and an emerging carbon-free energy carrier, yet its industrial synthesis via Haber-Bosch consumes similar to 1% of global energy. Photocatalytic nitrogen fixation provides a potential alternative, but conventional processes operate in aqueous media and yield trace concentrations of ammonia that are impractical to collect and use. Here, we introduce a photochemical looping strategy that integrates nitrogen activation, reduction, and solid-state capture in a cyclic process. Using a Pt-heteropolyacid-TiO2 composite, carbon monoxide, either supplied directly or produced in situ from CO2, generates oxygen vacancies on the heteropolyacid that adsorb and activate N-2, while water supplies protons and regenerates the vacancies. The formed ammonia is stored as a stable ammonium salt, which can be released upon calcination to produce aqueous NH3 solutions up to 1.3 wt%, which is significantly higher than the typically reported concentrations in the direct photocatalytic N-2 reduction in aqueous suspensions. By coupling photocatalysis with solid-state storage, this looping approach overcomes long-standing barriers in conversion, selectivity, and product recovery, establishing a scalable framework for solar-driven ammonia production under mild conditions.

Abstract Selective photocatalytic oxidation of methane to liquid oxygenates under ambient conditions remains challenging due to the inert C–H bond and propensity for over-oxidation. Controlling carrier transfer and reactive oxygen species is therefore essential to the selective methane photooxidation. Ultrasmall zirconium metal–organic framework (UiO-66-H) nanocrystals in situ grown on titania form a heterojunction that promotes efficient charge separation and tunes the interfacial band alignment. Comprehensive experiments and characterization reveal that this heterojunction precisely regulates • OH and • OOH generation, enabling controlled, radical-mediated oxidation of methane with a competitive oxygenate yield and nearly 100% selectivity at room temperature using air as an oxidant. In this work, ultrasmall metal–organic framework–semiconductor heterojunctions with a built-in electric field provide an effective route for developing efficient, low-cost photocatalysts for methane chemical valorization under mild, solar-driven conditions.

Easily accessible single-site surface nickel-alkyl complexes have been synthesized on silica partially dehydroxylated at 700 degrees C following a simple and robust method consisting of the reaction of (PMe3)2Ni(CH2SiMe3)2, (py)2Ni(CH2SiMe3)2, or (bpy)Ni(CH2SiMe3)2 with the remaining OH groups of the partially dehydroxylated silica support. In addition to mass balance analysis, infrared and solid-state NMR spectroscopic studies allowed us to define precisely the three surface species and, in particular, the alkyl active site, which is expected to initiate the oligomerization reaction of ethylene. Precatalysts were combined with a simple Lewis acid (AlCl3) to induce catalytic activity. This combination constitutes an efficient oligomerization catalyst reaching activities as high as 29, 900 mol of ethylene converted per mol of Ni per hour. The crucial role of AlCl3 beyond simple Lewis base abstraction in the activation of the catalyst precursor has been evidenced.

Upon illumination, photocatalysts generate charge carriers for redox reactions, but their efficiency is often limited by carrier recombination and poor minority-carrier diffusion, despite many existing junction engineering strategies. Here we exploit the insulator-metal transition in VO2 to produce a material that promotes efficient charge separation and enhances the photocatalytic conversion of methane through the spontaneous formation of junctions. We find that the photocatalytic activity peaks at the critical temperature of the transition, which we attribute to coexisting insulating and metallic domains with non-integer dimensional boundaries and sizes smaller than the minority-carrier diffusion length. Increasing the charge-separating interface length by decreasing the film thickness improves the photocatalytic activity and C-C coupling between alkoxy intermediates, leading to a propane selectivity of 100%. Moreover, electrically triggering the phase transition at lower temperatures further boosts methane conversion via field-assisted carrier activation. Overall, the metal-insulator transition provides an effective alternative to complex nanoscale junction engineering in photocatalysis.

Glycolaldehyde (GA) is an important C2 oxygenate and a versatile building block for the synthesis of pharmaceuticals, polymers, and fine chemicals. However, conventional GA production routes, including biomass pyrolysis and catalytic transformations, typically suffer from low selectivity, harsh reaction conditions, and limited scalability. Here, we demonstrate a photocatalytic route to GA from ethylene, driven by lattice oxygen exchange over SnO2 under oxidative aqueous conditions. This strategy achieves a GA yield of 4017 mu mol & centerdot;g-1 with 75% liquid-phase selectivity at ambient temperature and moderate pressure. We investigated the reaction mechanism by density functional theory (DFT) calculation, in synergy with experimental analysis. The formation of C2 oxygenates proceeds through a radical-mediated oxidation mechanism involving center dot OH and lattice oxygen. During the reaction, product desorption generates oxygen vacancies that are efficiently replenished under light irradiation through catalyst regeneration by molecular oxygen. These findings highlight the role of mobile lattice oxygen in steering selective photocatalytic oxidation and provide insights for the design of catalysts for selective alkene oxidation and oxygenate synthesis.

Toxic metal and dye contamination represent significant threats to aquatic ecosystems, emphasizing the need for effective water treatment methods. Hydroxyapatite-based metakaolin geopolymers (G-HGP) have shown promise as sorbents for removing such pollutants. This study introduces an eco-friendly acetic acid treatment to enhance the surface properties, texture, and adsorption capacity of G-HGP granules for the removal of Cd(II), Cr(III), and methylene blue (MB) dye. Characterization of untreated (G-HGP) and acetic acid-treated (G-HGP/AA) granules revealed notable improvements: a reduction in the pH at the point of zero charge (pHpzc) from 9.3 to 7.0, total porosity increased by 75 %, and significant gains in specific surface area (53.89 to 90.93 m2/g) and pore volume (0.20 to 0.38 cm3/g). Scanning electron microscopy (SEM) confirmed these morphological and textural improvements. Adsorption experiments demonstrated that acetic acid treatment significantly enhanced the removal efficiency of Cd(II), Cr(III), and MB dye, with maximum adsorption capacities of 80.69 mg/g for Cd(II), 69.52 mg/g for Cr (III), and 72.96 mg/g for MB dye. Notably, MB dye exhibited the highest adsorption efficiency, which was consistent with Density Functional Theory (DFT) analysis, indicating its higher reactivity, a smaller energy gap, higher electrophilicity, and lower back-donation energy compared to Cd(II) and Cr(III). The G-HGP/AA granules showed effective reusability over 8 cycles for Cr(III), 6 cycles for Cd(II), and 12 cycles for MB dye. This study highlights the efficacy of acetic acid treatment in improving the porosity of G-HGP granules and their potential in mitigating toxic metals and dye pollution in water.

This study presents a novel approach to addressing challenges of photocatalysy by TiO2 powder and the adsorption of anionic pollutants by geopolymers (GP) through the development of granules based on hydroxyapatite-geopolymer (HAP-MK-GP) materials. The synthesized HAP-MK-GP/Fe3O4-TiO2 granules exhibit promising physicochemical properties, including a high porosity of 0.25 cm3 /g, a specific surface area of 106.59 m2/g, notable magnetic behavior (saturation magnetization of 18.89 emu/g), and strong mechanical integrity (compressive strength of 1.63 MPa). The adsorption kinetics and equilibrium data for Direct Red 23 (DR23) dye and hexavalent chromium (Cr(VI)) conformed to the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer adsorption on a homogeneous surface. The maximum adsorption capacities were determined as 15.23 mg/g for DR23 and 36.06 mg/g for Cr(VI) under the following conditions: pH of 3, temperature of 21 degrees C, adsorbent dosages of 4 g/L for DR23 and 2 g/L for Cr(VI), and initial pollutant concentrations of 100 mg/L. Under UV irradiation, the granules demonstrated high photocatalytic efficiency for DR23 degradation, achieving removal rates exceeding 95 % under optimized conditions: pH of 3, temperature of 21 degrees C, 4 g/L of dose, and [DR23] 0of 50mg/L. Electron paramagnetic resonance (EPR) confirmed the generation of reactive radicals (center dot OH and O2 center dot-), crucial for photocatalytic activity. Chemical oxygen demand (COD) and total organic carbon (TOC) analyses corroborated the significant mineralization of DR23 dye. These findings underscore the potential of HAP-MK-GP/Fe3O4-TiO2 granules as a highly efficient dual-function photocatalyst-adsorbent material for wastewater treatment applications.

Aliphatic diols such as ethylene and propylene glycol are the key products in the chemical industry for manufacturing polymers. The synthesis of these molecules usually implies sequential processes, including epoxidation of olefins using hydrogen peroxide or oxygen with subsequent hydrolysis to glycols. Direct hydroxylation of olefins by cheap and green oxidants is an economically attractive and environmentally friendly route for the synthesis of diols. Here, we report a photocatalytic reaction for the dihydroxylation of ethylene and propylene to their glycols at room temperature using water as the oxidant. The photocatalyst contains Pd clusters stabilized by sub-nanometric polyoxometalate with TiO2 as the host material. Under light irradiation, it results in production rates of ethylene glycol and propylene glycols of 146.8 mmolgPd-1h-1 and 28.6 mmolgPd-1h-1 with liquid-phase selectivities of 63.3 % and 80.0 %, respectively. Meanwhile, green hydrogen derived from water is produced as another valuable product. Combined spectroscopy investigation suggests that the reaction proceeds via pi-bonded adsorption of olefins over Pd clusters with hydroxylation by hydroxyl radicals formed by photocatalytic dissociation of water. A direct, selective photocatalytic method for synthesizing glycols from olefins at room temperature uses water as the oxidizing agent and H2 as byproduct. The hydroxylation proceeds by hydroxyl radicals formed by photocatalytic dissociation of water.

Methane, abundant but inert, contributes significantly to greenhouse gases, primarily through combustion, which emits vast amounts of CO2. Photocatalytic methane coupling at ambient temperature offers a method to convert it into ethane, a more versatile hydrocarbon. This study examines selective methane-to-ethane coupling using heterogeneous photocatalysts comprising silver and palladium salts dispersed on titania. Through a combination of ex-situ and in-situ techniques along with DFT simulations, distinct mechanisms and active phases in these catalysts are revealed. In silver catalysts, dispersed cationic Ag+ species are crucial for methane activation, while in palladium catalysts, palladium primarily exists in metallic form during coupling. Water strongly enhances coupling rates with both catalysts. DFT modeling identified methane adsorption sites, suggesting methane activation via center dot OH radicals, experimentally supported by EPR under in-situ conditions.

The effective conversion of methane to a mixture of more valuable hydrocarbons and hydrogen under mild conditions is a significant scientific and practical challenge. Here, we synthesized Zn-containing nanosized MFI zeolite for direct oxidation of methane in the presence of H2O and air. The presence of the surface hydroxyl groups on nanosized MFI-type zeolite and their significant reduction in the Zn-containing nanosized MFI zeolite were confirmed with Infrared Fourier Transform (FTIR) spectroscopy. Incorporation of zinc atoms into the framework of nanosized MFI zeolite is revealed by Nuclear Magnetic Resonance, X-ray Diffraction and UV-Vis Spectroscopy. Unexpectedly, pure silica MFI zeolite exhibited the highest photocatalytic performance. Our findings demonstrated that large number of isolated silanol groups and silanol nests increase the formation of ⋅OH, and enhance the productivity of oxygenate compounds and C2H6, while the Zn incorporated into the zeolite framework or attached to the silanol nests of the nanosized zeolites are less efficient. A mechanism of photocatalytic methane oxidation is proposed. These findings provide insights into the development of active nanosized zeolite photocatalysts with an extended amount of surface hydroxyl groups that can play a key role in photocatalytic methane conversion.

The mixture of ammonium polyphosphate and pentaerythritol is a very efficient intumescent system suitable for polyolefins, especially polypropylene. In this article, the intumescence mechanism of this intumescent system with and without zeolite 4A used as a synergy agent is revisited. The intumescent system was investigated in depth using continuous-wave electron paramagnetic resonance spectroscopy, solid-state nuclear magnetic resonance, and the advanced technique, namely hyperfine sublevel correlation pulsed electron paramagnetic resonance. It was observed that the char generated between 250°C and 350°C is made of polycyclic heterocyclic radicals with nitrogen atoms and that free radicals are mainly generated at these temperatures with a spin concentration relatively stable at least up to 500°C. Moreover, the presence of hydrogen, carbon, nitrogen, and phosphorus was clearly evidenced in the chemical environment of free electrons at 350°C (hyperfine sublevel correlation pulsed electron paramagnetic resonance). Besides, it was also evidenced that 4A totally collapses below 250°C. Contrary to previous works suggesting the presence of aluminosilicophosphate complexes, this work demonstrated that distinct alumino- and silicophosphate complexes are generated and protected the residue at high temperatures.

Direct functionalization of methane selectively to value-added chemicals is still one of the main challenges in modern science. Acetic acid is an important industrial chemical produced nowadays by expensive and environmentally unfriendly carbonylation of methanol using homogeneous catalysts. Here, we report a new photocatalytic reaction route to synthesize acetic acid from CH4 and CO at room temperature using water as the sole external oxygen source. The optimized photocatalyst consists of a TiO2 support and ammonium phosphotungstic polyoxometalate (NPW) clusters anchored with isolated Pt single atoms (Pt1). It enables a stable synthesis of 5.7 mmol·L-1 acetic acid solution in 60 h with the selectivity over 90% and 66% to acetic acid on liquid-phase and carbon basis, respectively, with the production of 99 mol of acetic acid per mol of Pt. Combined isotopic and in situ spectroscopy investigation suggests that synthesis of acetic acid proceeds via a photocatalytic oxidative carbonylation of methane over the Pt1 sites, with the methane activation facilitated by water-derived hydroxyl radicals.

Nickel salts of Keggin heteropolytungstates with the general formula Ni( x )A( y )W(12-y )O(39or40) (A = Si/P) were synthesized and studied as bulk catalytic materials or supported ones by deposition on modified and functionalized clay minerals (pillared layered clay and porous clay heterostructure). Characterizations by Raman, P-31 and Si-29-NMR, and ESEM-EDS techniques showed that pure and supported systems preserved the Ni/W ratio and the expected structural properties of heteropolyanions. These materials were evaluated as catalysts in the selective oxidation of sulfides to sulfoxides or sulfones, using aqueous hydrogen peroxide and mild reaction conditions. The bulk materials, with a higher content of Ni, displayed a remarkable catalytic behavior in the oxidation of diphenyl sulfide (Ni3PW11NiO40H, 90% conversion in 15 min at 75?, 100% sulfone selectivity in 3 h). Supported catalysts, particularly the non-functionalized PCH (Ni2SW12O40/PCH), showed excellent activity, with also being selective in the oxidation of sulfide to sulfoxide (87% conversion, 88.9% sulfoxide selectivity). The reuse of these materials was studied in the optimum reaction conditions, resulting in similar activity and selectivity.

In this study, we reported the photocatalytic removal of Rhodamine B dye from aqueous solution by TiO2 polymorph powders under UV light illumination. The work primarily highlights the physico-chemical properties of TiO2 semiconductors. X-ray diffraction (XRD) patterns confirmed the presence of anatase, rutile, and a mixture anatase–rutile phases. The nitrogen gas sorption analysis gives BET surface area with highest value obtained with anatase polymorph (74 m2/g). According to the ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) study, anatase, rutile, and mixture had band gap energies of 3.35, 2.99, and 3.20 eV, respectively. The photoluminescence and the spin trapping results showed a weaker recombination of photoinduced charge carriers and a highest amount of hydroxyl OH• and superoxide O2−• radicals with anatase polymorph. The effect of the catalyst nature and loading on the photocatalytic degradation of Rhodamine B were investigated. The results demonstrated that the maximum rate of Rhodamine B degradation was 99.4

Methane, one of the most abundant molecules on Earth and a major greenhouse gas, comes from renewable and fossil resources. The utilization of methane as a starting material for synthesis of chemicals is attractive but encounters numerous challenges due to high thermodynamic stability and extreme inertness of methane. Most of methane reactions occur at high temperatures and coincide with major emissions of CO2. Semiconductor photocatalysis offers an efficient alternative for methane conversion at room temperature. In this paper, we studied the plasmonic gold nanoparticles (NPs) with size from 6 nm to 60 nm supported on titania semiconductor in methane nonoxidative and oxidative couplings and elucidated their roles in the reactions. Strikingly, an efficient oxidative coupling with ethane production of 819 mmol/g/h and a coupling selectivity up to 86% was achieved in a flow reactor under optimized conditions. The reaction proceeded through methane activation over oxygen vacancies on Ultravioletexcited titania. Gold NPs played important roles in charge separation and provided sites for soft oxygen activation. The size of gold NPs was found to be not noticeably affecting methane coupling.(c) 2023 Elsevier Ltd. All rights reserved.

Methane valorization is one of the main challenges in the modern chemical industry. However, existing processes require high reaction temperatures. The alternative photocatalytic routes for methane valorization at ambient conditions would be highly attractive. Today, photovoltaic (PV) generation of electricity is one of the main sources of renewable energy. PV absorbers could be excellent candidates for photochemical applications. Herein, we report selective methane photocatalytic oxidation at ambient conditions into CO and H2 by conventional Cu(In,Ga)Se2 (CIGS) absorbers used in solar cells. A thin film of CIGS coated over Mo exhibits exceptional performance in methane partial oxidation to CO and H2 with a stable CO productivity of 2.4 mmol per gram of CIGS and a selectivity to CO of over 80%. The reaction proceeds via the facile dissociation of methane into disordered carbon and hydrogen over CIGS surface with subsequent regeneration of the surface by partial oxidation of carbon into CO.

Pure ZnO and erbium (1, 3 and 5 at.%) doped ZnO nanoparticles aerogels were synthesized by sol-gel in supercritical drying conditions of isopropanol. The aim of this work is the study of the erbium effects on structural, optical and photocatalytic properties of ZnO aerogels using various physicochemical techniques. The photocatalytic degradation of Methylene Blue (MB) under UV light irradiation is significantly enhanced with the introduction of Er3+ ions into the structure with an optimum obtained with 1 and 3 at. % erbium concentration, with almost a complete degradation after 100min of UV irradiation. These results are in good agreement with those obtained by EPR spin trapping measurements where the highest amount of hydroxyl radicals •OH, responsible for the degradation of MB, is observed with ZnO doped with 1 and 3 at. % erbium. A decrease of the electron-hole pairs recombination rate was confirmed by PL analyses in the Er doped samples, due to the high interactions between Er3+ ions which lead to an increase of the non-radiative process originated from PL quenching. In fact, the photogenerated electrons are trapped at the energy levels created by the defects in the band gap of ZnO.

Direct conversion of methane into fuels and chemicals remains a ma-jor challenge in modern science. Formic acid is one of the most promising platform molecules. Photocatalysis proposes an attrac-tive route for methane partial oxidation under mild conditions. The radical mechanism of methane photocatalytic oxidation re-stricts the selectivity to target products. In this article, we propose a strategy to break conventional limitations of methane photocata-lytic oxidation by adding a thermocatalyst and conducting the process in a one-pot reactor. In this strategy, the methane selective conversion into formic acid proceeds first over cesium salt of phosphotungstic acid on titania, which photocatalytically oxidizes methane into a mixture of C1 oxygenates. These oxygenates are then selectively converted into formic acid over a heterogeneous alumina-supported ruthenium catalyst. All reactions occur at room temperature in the same reactor. A selectivity to formic acid of 85% and a productivity of 5 mmol g-1 photocatalyst are achieved.