Ni-modified molybdenum zirconia (Ni/MoO₃/ZrO₂) was developed as an effective oxygen storage material for chemical looping dry reforming of methane (CL–DRM) under isothermal reaction conditions of 650 °C, which was 100–200 °C lower than the previously reported oxide-based materials.

Abstract

We investigated supported-MoO₃ materials effective for the chemical looping dry reforming of methane (CL–DRM) to decrease the reaction temperature. Ni-modified molybdenum zirconia (Ni/MoO₃/ZrO₂) showed CL–DRM activity under isothermal reaction conditions of 650 °C, which was 100–200 °C lower than the previously reported oxide-based materials. Ni/MoO₃/ZrO₂ activity strongly depends on the MoO₃ loading amount. The optimal loading amount was 9.0 wt.% (Ni/MoO₃(9.0)/ZrO₂), wherein two-dimensional polymolybdate species were dominantly formed. Increasing the loading amount to more than 12.0 wt.% resulted in a loss of activity owing to the formation of bulk Zr(MoO₄)₂ and/or MoO₃. In situ Mo K-edge XANES studies revealed that the surface polymolybdate species serve as oxygen storage sites. The Mo⁶⁺ species were reduced to Mo⁴⁺ species by CH₄ to produce CO and H₂. The reduced Mo species reoxidized by CO₂ with the concomitant formation of CO. The developed Ni/MoO₃(9.0)/ZrO₂ was applied to the long-term CL–DRM under high concentration conditions (20 % CH₄ and 20 % CO₂) at 650 °C, with two pathways possible for converting CH₄ and CO₂ to CO and H₂ via the redox reaction of the Mo species and coke formation.

Water splitting is viewed as a clean substitute for fossil fuels and as the most promising approach for quickly producing hydrogen fuel. The oxygen evolution process (OER), which yields oxygen as the sole byproduct at the anode of a water electrolyzer, also yields hydrogen at the cathode. In this work, we proposed a facile synthetic route to prepare a nanostructured Co-based material for OER via a simple chemical method.

Abstract

To combat with energy crisis considering clean energy, oxygen evolution reaction (OER) is crucial to implement electrolytic hydrogen fuel production in real life. Here, straightforward chemical synthesis pathways are followed to prepare cobalt tetraoxide nanoparticles (Co₃O₄NPs) in an alkaline OER process using poly[(2-methacryloyloxy)ethyl]trimethylammonium chloride (Co₃O₄NPs@PMTC) as support to prevent aggregation. In material characterization, the X-ray diffraction (XRD) pattern confirms the crystallinity of the synthesized Co₃O₄NPs@PMTC, and Raman spectroscopy indicates that the Co₃O₄NPs contain cubic close-packed oxides. The morphological analysis reveals the wrinkle-like disruption which is distributed evenly owing to the folded nanosheet arrays. Energy-dispersive X-ray spectroscopy indicates the presence of a significant number of cobalt atoms in the Co₃O₄NPs, and elemental mapping analysis demonstrates the composition of the NPs. At a current density of 10 mA cm⁻², oxygen is emitted at 1.67 V delivering an overpotential of 440 mV. This unique structure of Co₃O₄NPs@PMTC provides beneficial functions that are responsible for a large number of active sites and the rapid release of oxygen gas with long-term stability. Through kinetic study, we found a Tafel slope of 48.9 mV dec⁻¹ which proves the catalytic behavior of Co₃O₄NPs@PMTC is promising toward the OER process.

Bisphosphoniostannylenes and plumbylenes have been embedded into [3]ferrocenophane scaffolds staying monomeric for the stannylenes and dimerice via halide bridges for the plumbylene. The compounds are dynamic in solution which can be suspended with weakly coordination anions.

Abstract

Donor stabilization of Sn(II) and Pb(II) halides with 1,1’-ferrocenylene bridged bisphosphanes has been explored for Fe(C₅H₄P(C₆H₅)₂)₂ (dppf), and Fe(C₅H₄PH(C₄H₉))₂. These bisphosphanes are reacted with SnBr₂ and PbCl₂ with and without additional Lewis acid (AlCl₃) forming acyclic and cyclic donor adducts from which the latter represent bisphosphoniotetrylenes. Since dynamic exchange in solution is observed, characterization includes solution and solid-state NMR in addition to SC-XRD, amended by DFT calculations.

N,N’-bis(2-aminobenzophenone)-1,4,5,8-naphthalenetetracarboxylic diimide (1) can dissolve in aqueous solutions via complexation with λ-carrageenan and the complex could include small aromatic guest molecules such as benzene, toluene, and xylene with sufficient fluorescence response in aqueous solution.

Abstract

To detect small aromatic molecules in water, we prepared functional host molecules based on water-soluble N,N’-bis(2-aminobenzophenone)-1,4,5,8-naphthalenetetracarboxylic diimide (1) and a solubilizing agent using a high-speed vibration milling apparatus. The fluorescence response of host 1-solubilizing agent complexes before and after extraction of small aromatic guest molecules was large and the fluorescence maxima were dependent on the small aromatic guest molecules.

Increasing energy demands and fossil fuel depletion urges scientists to develop renewable catalysts for energy production. Amorphous catalysts are the emerging electrocatalysts due to their structural flexibility. Herein, crystalline LaCoO₃ is transformed to amorphous by urea reduction treatment. The catalyst synthesized at 450 °C (LCO-4) exhibits excellent OER activity.

Abstract

Amorphous inorganic perovskites have attracted significant attention as efficient electrocatalysts due to their unique structural flexibility and good catalytic activity. In particular, the disordered structure and a surface rich in defects such as oxygen vacancies can contribute to the superior electrocatalytic activity of amorphous oxides compared to their crystalline counterpart. In this work, we report the synthesis of LaCoO₃, followed by an amorphization process through urea reduction with tailored modifications. The as-synthesized catalysts were thoroughly tested for their performance in oxygen evolution reaction (OER), Remarkably, the amorphous LaCoO₃ synthesized at 450 °C (referred to as LCO-4) exhibits excellent OER catalytic activity. At an overpotential of 310 mV, it achieved a current density of 10 mA/cm⁻², exceedingly fast to 1 A/cm⁻² at an overpotential of only 460 mV. Moreover, LCO-4 exhibited several advantageous features compared to pristine LaCoO₃ and LaCoO₃ amorphized at other two temperatures (350 °C, LCO-3, and 550 °C, LCO-5). The amorphized LCO-4 catalyst showed a higher electrochemically active surface area, a key factor in boosting catalytic performance. Additionally, LCO-4 demonstrated the lowest Tafel slope of 70 mVdec⁻¹, further highlighting its exceptional OER activity. Furthermore, the long-term stability of LCO-4 is notably superior than pristine LaCoO₃ (LCO-P) and the other amorphized samples (LCO-3 and LCO-5). The enhanced catalytic activity of LCO-4 can be attributed to its unique disordered structure, small crystallite size, and higher concentration of oxygen vacancies in the final catalyst.

The illustrative description for the synthesis method of CZTS and their distinctive morphological effects are explained in this review. The potential scope of CZTS utilization in wastewater-cleaning through photocatalytic dye-degradation is thoroughly narrated. A comparative analysis of CZTS nanocomposites is provided to indicate its future prospective as a promising material for hydrogen evolution, thus motivating researchers to investigate in this new direction.

Abstract

A variety of unique compounds have been examined to accommodate the current demand for useful multi-functional nanomaterials, copper-based quaternary CZTS semiconductors are one of them. Due to their special characteristic features like non-toxicity, cheap, and abundance, they have been recommended in recent literature for various applications. Apart from individual CZTS, different hetero-structures have also been prepared with different compounds which is well discussed and elaborated in this article. Additionally, their preparation methods, properties, and application viability have also been discussed comprehensively. The application of CZTS such as photocatalytic dye degradation and hydrogen evolution reaction has been elaborated on in this article identifying their benefits and challenges to give readers a thorough visualization. Apart from that, challenges reported in studies, a few approaches are also mentioned to possibly counter them.

Herein, for the first time we have explored the umpolung reactivity of vinylogous carbon center of diazo arylidene succinimide (DAS) through rhodium catalysis to achieve [2,3]-Stevens rearrangement of α-thioether esters. The protocol has successfully demonstrated the distal C-H bond functionalization of the α-thioether esters. Alongside, the carbenoid reactivity of DAS has also been achieved with Doyle-Kirmse reaction of allyl/propargyl phenyl sulfides. The protocol proved to be practical to synthesize a wide variety of [2,3]-Stevens rearrangement products exclusively and the possible side products emanating from Pummerer rearrangement and [1,2]-Stevens rearrangement were not observed. This catalytic protocol works smoothly in environmentally benign solvent under open air to afford the corresponding desired products with excellent diastereo-, regio- and chemo-selectivities in good to excellent yields. The protocol also proved to be scalable on gram quantity.

The presence of three transition metal oxides in a nanocomposite made it possible to have higher catalytic CO oxidation than that of two. At higher annealing temperatures, the obtained nanocomposite had more crystallinity and thus exhibited lower activity toward the oxidation of CO. The 50 % CO conversion was observed at about 82 °C for the CuO−MnO_x−Fe₂O₃-300 catalyst.

Abstract

By using a simple co-precipitation method, new Fe₂O₃-based nanocatalysts (samples) were synthesized. The samples were composites of two or three transition metal oxides, MO_x (M=Fe, Mn, Co, Ni, and Cu). The average size of CuO crystallites in the composites composed of two oxide components (CuO−Fe₂O₃) was about 14.3 nm, while in those composed of three (CuO−MnO_x−Fe₂O₃), the composite's phase compositions were almost in the amorphous form when annealing the sample at 300 °C. The latter sample had a specific surface area higher than that of the former, 207.9 and 142.1 g/m², respectively, explaining its higher catalytic CO oxidation. The CO conversion over the CuO−MnO_x−Fe₂O₃-300 catalyst (1 g of catalyst, 2600 ppm of CO concentration in air, and 1.0 L/min of gas flow rate) begins at about 40 °C; the temperature for 50 % CO conversion (t ₅₀) is near 82 °C; and CO removal is almost complete at t ₉₉ ≈110 °C. The activity of the optimal sample was tested in different catalytic conditions, thereby observing a high durability of 99–100 % CO conversion at 130 °C. The obtained results were derived from XRD, FTIR, BET, SEM, elemental analysis and mapping, as well as catalytic experiments.

The preparation of pyrazinamide via catalytic hydration of 2-cyanopyrazine is of great economic interest with high atomic economy. Vanadium-nitrogen-carbon materials were fabricated and employed for catalytic hydration of 2-cyanopyrazine with unique substrate specificity. This work expands the application of vanadium-based catalysts for nitrile hydration reactions.

Abstract

Pyrazinamide is an important medicine used for the treatment of tuberculosis(TB). The preparation of pyrazinamide via catalytic hydration of 2-cyanopyrazine is of great economic interest with high atomic economy. Heterogeneous non-precious transition metal-catalyzed hydration of nitriles under neutral reaction conditions would be rather attractive. Herein vanadium-nitrogen-carbon materials were fabricated and employed for selective hydration of nitriles using water as both the solvent and reactant. 2-Cyanopyrazine could be smoothly converted into to pyrazinamide with unique substrate specificity. Additives with different N and O atoms could significantly affect hydration of 2-cyanopyrazine due to competitive adsorption/coordination in the reaction system. This work provides a new approach for non-precious metal catalyzed hydration of nitriles.

Research on the oxidation of furfural to maleic anhydride (MA) suffers from low efficiency, solvent corrosion, and harsh conditions. CuO_x/Nb₂O₅ was prepared as photocatalyst to catalyze furfural oxidation to MA and 5-hydroxy-2(5H)-furanone (HF) selectively, and can absorb visible light due to the ligand to metal charge transfer (LMCT) with adsorbed furfural molecules.

Abstract

Maleic anhydride (MA) is an important polyester monomer that can be produced from oxidizing renewable furfural derived from biomass. However, MA generation from furfural requires harsh reaction conditions, and suffers from low efficiency and solvent corrosion. Herein, we design a Nb₂O₅ photocatalyst loaded of highly dispersed CuO_x (CuO_x/Nb₂O₅), which selectively catalyzes furfural oxidation to MA and the precursor (5-hydroxy-2(5H)-furanone, HF). Due to CuO_x loading and forming a complex of ligand to metal charge transfer (LMCT) between the Nb₂O₅ surface and adsorbed furfural, the CuO_x/Nb₂O₅ absorbs visible light to activate furfural though Nb₂O₅ has a large band-gap energy (3.2 eV). Singlet oxygen (¹O₂) is the key active species for C−C bond cleavage and CO generation. MA and HF is produced with a combined yield of 59 % under optimized conditions. This work provides a mild way to provide renewable maleic anhydride via oxidative C−C bond cleavage.