Oxidation Reaction Research Articles

Dual (oxy)hydroxide cocatalyst synergistically boosts solar water splitting of BiVO4 photoanode.

Bismuth oxide (BiVO4) is considered one of the most promising semiconductors for photoelectrochemical (PEC) water splitting due to its highly theoretical photocurrent of 7.5 mA cm-2. However, its sluggish kinetics and severe photocorrosion still hinder the real application of a large-area BiVO4 photoanode. Herein, a room-temperature immersion method has been used to fabricate a dual cocatalyst-coated BiVO4 film, namely the BiVO4/FeOOH/Co(OH)2 photoanode. This composite photoanode delivers a photocurrent density of 2.56 mA cm-2, which is 2.7 times that of pure BiVO4. After a long-term testing of 10 h, its retention rate of photocurrent reaches 71.63%, which is 4.6 times that of BiVO4. The kinetic studies illustrate that dual cocatalyst can significantly lower the charge transfer resistance, improve the charge injection efficiency, and reduce the Tafel slope. Specifically, FeOOH plays a role in transporting photogenerated holes, while Co(OH)2 facilitates water oxidation reactions. In addition, the dual cocatalyst coating can slow down vanadium ion dissolution and improve PEC stability. This immersion method can easily be applied to large-area photoelectrodes.

Hollow Pt-Encrusted RuCu Nanocages Optimizing OH Adsorption for Efficient Hydrogen Oxidation Electrocatalysis.

As one of the best candidates for hydrogen oxidation reaction (HOR), ruthenium (Ru) has attracted significant attention for anion exchange membrane fuel cells (AEMFCs), although it suffers from sluggish kinetics under alkaline conditions due to its strong hydroxide affinity. In this work, we develop ternary hollow nanocages with Pt epitaxy on RuCu (Pt-RuCu NCs) as efficient HOR catalysts for application in AEMFCs. Experimental characterizations and theoretical calculations confirm that the synergy in optimized Pt8.7-RuCu NCs significantly modifies the electronic structure and coordination environment of Ru, thereby balancing the binding strengths of H* and OH* species, which leads to a markedly enhanced HOR performance. Specifically, the optimized Pt8.7-RuCu NCs/C achieves a mass activity of 5.91 A mgPt+Ru-1, which is ~3.3, ~2.2, and ~15.0 times higher than that of RuCu NCs/C (1.38 A mgRu-1), PtRu/C (1.83 A mgPt+Ru-1) and Pt/C (0.37 A mgPt-1), respectively. Impressively, the specific peak power density of fuel cells reaches 15.9 W mgPt+Ru-1, significantly higher than those of most reported PtRu-based fuel cells.

Cooperative Active Sites on Ag2Pt3TiS6 for Enhanced Low-Temperature Ammonia Fuel Cell Electrocatalysis.

Ammonia has attracted considerable interest as a hydrogen carrier that can help decarbonize global energy networks. Key to realizing this is the development of low temperature ammonia fuel cells for the on-demand generation of electricity. However, the efficiency of such systems is significantly impaired by the sluggish ammonia oxidation reaction (AOR) and oxygen reduction reaction (ORR). Here, we report the design of a bifunctional Ag2Pt3TiS6 electrocatalyst that facilitates both reactions at mass activities exceeding that of commercial Pt/C. Through comprehensive density functional theory calculations, we identify that active site motifs composed of Pt and Ti atoms work cooperatively to catalyze ORR and AOR. Notably, in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) experiments indicate a decreased propensity for *NOx formation and hence an increased resistance toward catalyst poisoning for AOR. Employing Ag2Pt3TiS6 as both the cathode and anode, we constructed a low temperature ammonia fuel cell with a high peak power density of 8.71 mW cm-2 and low Pt loading of 0.45 mg cm-2. Our findings demonstrate a pathway towards the rational design of effective electrocatalysts with multi-element active sites that work cooperatively.

Optically Active Sulfoxides from 2(5H)-Furanone and Monoterpene Alcohols: Synthesis, Structure, and Antibacterial Activity

A series of optically active 5(S)-(l-bornyloxy)- and 5(S)-(l-menthyloxy)-2(5H)-furanones with an arylthio group at the C(4) position of the γ-lactone ring was synthesized and studied for its oxidation reactions with various reagents. Novel 2(5H)-furanone sulfoxides were obtained as mixtures of two diastereoisomers through the oxidation of arylthioethers with m-chloroperbenzoic acid (m-СРВА) or hydrogen peroxide in acetic acid. Individual stereoisomers of these sulfoxides were isolated using recrystallization and high-performance liquid chromatography (HPLC) and characterized by IR and NMR spectroscopy. The molecular structures of eight stereoisomerically pure compounds were confirmed by X-ray diffraction (XRD) analysis. The antibacterial activity of the novel sulfoxides against Staphylococcus aureus and Escherichia coli was assessed, with a number of compounds found to inhibit bacterial growth and biofilm formation in S. aureus.

CO Oxidation over Cu/Ce Binary Oxide Prepared via the Solvothermal Method: Effects of Cerium Precursors on Properties and Catalytic Behavior

Cu/Ce binary oxides were prepared via the one-pot solvothermal method, and the effects of different cerium precursors (cerium nitrate and cerium ammonium nitrate) on the catalytic activity and resistance to water vapor or CO2 of the prepared samples for low-temperature CO oxidation reaction were investigated. The physicochemical characteristics of the catalysts were characterized via thermal analyses (TG-DSC), X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption/desorption, inductively coupled plasma-atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs), and temperature-programmed reduction with H2 (H2-TPR). The results indicated that the CuO/CeO2 catalyst (CC-N) prepared with cerium nitrate showed higher activity for low-temperature CO oxidation, which can be ascribed to its larger specific surface area and pore volume, higher amounts of highly dispersed CuO species with strong interaction with CeO2, Cu+ species, and more active surface oxygen species, compared with the counterpart prepared with cerium ammonium nitrate (CC-NH). Furthermore, the CC-N catalyst also exhibited better resistance to CO2 poisoning than CC-NH.

N‐Carbamimidoyl‐2,2,2‐Trifluoro‐N′‐Arylacetimidamides as Important Intermediates for the Synthesis of 3‐Amino‐4‐Aryl‐5‐(Trifluoromethyl)‐1H‐1,2,4‐Triazoles

ABSTRACTA novel series of N‐carbamimidoyl‐2,2,2‐trifluoro‐N′‐arylacetimidamides (3a–j) have been prepared via condensation of 2,2,2‐trifuoroacetimidoyl chlorides with guanidine in the presence Na and in dry EtOH solvent at ambient temperature. Then, these key intermediates were applied for the synthesized of 3‐amino‐4‐aryl‐5‐(trifluoromethyl)‐1H‐1,2,4‐triazoles (4a–j) under oxidative cyclization reaction in the presence of KI/I2 as an oxidant system and DMSO solvent. The target compounds were produced in high yields and without the need for isolation.

Endothelial cell phenotype is linked to endothelial dysfunction in individuals with a family history of type 2 diabetes.

The patient's family history of type 2 diabetes (FH-DM2) has been negatively associated with the functionality of endothelial cells (ECs). Our objectives in this work were to use human umbilical vein endothelial cells (HUVECs) as a model, to substantiate whether FH-DM2 influences endothelial phenotype and impairs NO and ROS synthesis, cell metabolism, and mitochondrial activity of ECs from individuals with FH-DM2. In this study were evaluated the synthesis of reactive oxygen species (ROS) and nitric oxide (NO), mitochondrial membrane potential (MMP), mRNA of eNOS, glucose consumption, and lactate synthesis in HUVECs from newborns with FH-DM2. Furthermore, we also evaluated EC complexity and cell size through flow cytometry. Our results showed significant differences in HUVECs with FH-DM2, regarding their complexity and cell size, in the synthesis of ROS (p<0.01), and NO (p<0.05); they also reflected diminished glucose consumption and slight changes in the lactate levels. In conclusion, our results showed that HUVECs from children with FH-DM2 have a reduced capability of synthesizing ROS and NO, which might be linked to the metabolism of endothelial cells. These results are relevant since early endothelial dysfunction has been reported in individuals with FH-DM2, and could be used to establish preventive measures to reduce the risk of developing atherosclerosis or cardiovascular diseases in healthy individuals, but with this family background.

How Ir–Rh Alloys Improve Electrochemical Ammonia Oxidation Activity Studied by Density Functional Theory

AbstractThe electrochemical ammonia oxidation reaction (AOR) has applications in hydrogen storage and ammonia waste remediation. Using density functional theory, we investigate the mechanism of AOR on Ir, Rh, and their alloys at varied atomic ratios (, , and ) toward (g), (aq), and (aq) formation. This work introduces a method for computational alloy design by considering both electronic energy and configurational entropy. The structures considered are selective to (g) formation and all favored *N–N coupling. An alloy was found to reduce the theoretical onset potential for (g) formation relative to pure Ir while not exhibiting a downhill coupling step corresponding to catalyst poisoning by *N as shown for pure Rh, consistent with previous experimental work. The formation of (aq) and (aq) demand significantly higher potentials, typically limited by the final hydroxylation step before desorption.

Covalent bidentate ligand-enabled regioselective Wacker-type oxidation of olefins.

The utilization of Pd(ii)-catalyzed oxidation for the transformation of terminal olefins into methyl ketones has emerged as a particularly intriguing and versatile strategy in organic synthesis. Herein we report a novel Pd(ii)-catalyzed Wacker-type oxidation with covalent bidentate ligands. The ligand, 1-(pyridin-2-yl)-1,2-dihydro-3H-indazol-3-one, exhibits excellent performance in converting olefins to ketones. The optimized reaction conditions include the use of TBHP as oxidant, EtOH or MeCN as solvent and short reaction time. The substrate scope includes various substituted olefins, which undergo the desired oxidation reaction with high efficiency.

A Review: Recent Advances in Chemistry and Applications of 2,4-Dihydroxybenzaldehyde Oxime and Its Transition Metal Complexes

This review presents a comprehensive overview of the recent advances in the chemistry and applications of 2,4-dihydroxybenzaldehyde oxime (DHBO) and its transition metal complexes. DHBO, characterized by its unique hydroxyl and oxime functional groups, has gained significant attention due to its versatile reactivity and potential applications across various fields, including pharmaceuticals, catalysis, and environmental science. Recent synthetic methodologies, including microwave-assisted techniques and green chemistry approaches, have improved the efficiency and sustainability of DHBO production. The formation of transition metal complexes with DHBO has been a focal point of research, revealing enhanced catalytic properties and biological activities compared to the free ligand. These complexes have shown promise in organic synthesis, particularly in oxidation and reduction reactions, as well as in drug development, exhibiting antimicrobial and anticancer properties. Furthermore, the potential of DHBO and its metal complexes in environmental remediation, particularly in removing heavy metals and pollutants, underscores their significance in addressing contemporary environmental challenges. This review also provides current knowledge on the synthesis, characterization, and applications of DHBO and its transition metal complexes, highlighting their importance in both academic research and industrial applications. By elucidating the multifaceted roles of DHBO, this work aims to pave the way for future research and innovation in this promising area of study.

Facet-dependent spatial separation of dual cocatalysts on MOF photocatalysts for H2O2 production coupling biomass oxidation with enhanced performance

Cooperative coupling of photocatalytic two-electron oxygen reduction reaction (2e-ORR) with oxidative organic synthesis holds great promise for sustainable production of valuable chemicals. To achieve high performance, the rational design of photocatalysts with effective electron-hole separation and redox capability is crucial. Herein, a MOF-based photocatalyst with crystal facet-dependent spatial separation of dual cocatalysts is constructed for photocatalytic 2e-ORR coupled with vanillyl alcohol oxidation reaction (VAOR). The facet-dependent growth of reductive Pd and oxidative CoOx cocatalysts respectively on the {100} and {001} facets of MIL-125-NH2 enables the directional migration of photogenerated carries, facilitating the charge separation for redox reactions. Additionally, the interaction between Pd and MIL-125-NH2 modulates the Pd sites into electron-sufficient state with upshifted d-band center, promoting the O2 activation and *OOH intermediate formation. The rationally designed composite photocatalyst delivers an excellent H2O2 yield of 74.8 mM g−1 h−1 and a high vanillic acid production rate of 80.9 mM h−1 g−1 with the conversion and selectivity of 96.8 % and 91.1 %, respectively.

Origin of Performance Decline in Carbonated Anion Exchange Membrane Fuel Cells.

Anion exchange membrane fuel cells (AEMFCs) have successfully eliminated anode carbonate precipitation through cation immobilization with the incorporation of alkaline polymer electrolytes (APEs). However, carbonation by CO2 in ambient air continues to induce significant AEMFC performance losses via mechanisms that remain unclear/elusive. In this multimodal investigation of AEMFC carbonation, we find that the increase in ionic resistance after carbonation accounts for only a small fraction of the cell voltage drop, especially at high current densities. Controlled anode and cathode carbonation tests indicated that the anode hydrogen oxidation reaction (HOR) was significantly impeded by carbonation. Hydrogen pump tests showed that the HOR kinetics were more than an order of magnitude lower after carbonation, thus accounting for the large decrease in the cell voltage. Further studies using the electrochemical quartz crystal microbalance (EQCM) revealed that there exists a large barrier to the rearrangement of the double layer at the Pt/ionomer interface in the hydrogen underpotential deposition (HUPD) region, which may explain the slower HOR kinetics after carbonation. These results provide fundamental insight into the unique properties of the catalyst/APE interface and suggest new directions for energy materials and technology developments.

Synergistic Inclusion of Reaction Activator and Reaction Accelerator to Ni-MOF Toward Extra-Ordinary Performance of Urea Oxidation Reaction.

Recently electrochemical urea oxidation reaction (UOR) has emerged as the technology of demand for commercialization of urea-based energy conversion. However, the nascent idea is limited by the energy burden of threshold voltage and the sluggish reaction kinetics involving a six-electron transfer mechanism. Herein, for the first time, the engineering of electrocatalysts are proposed with simultaneous inclusion of UOR activator and UOR accelerator. Nitrogen-doped carbon-decorated Ni-based Metal Organic Framework (MOF)has been synthesized as the base catalyst material. MoO2 and rGO with varied loading have been attached to the MOF to get the desired MoO2/Ni-MOF/rGO heterostructure incorporating defects and crystal strain within the materials. Investigations reveal that the invoked lattice strain and atomic defects promote plenteous Ni3+ active sites. The optimized sample demonstrates extraordinary performance of UOR having the potential value as low as 1.32V versus RHE to reach the current density of 10mAcm-2 and the tafel slope is only 31mVdec-1 reflecting very fast reaction kinetics. Here MoO2 plays the role of UOR activator whereas optimized loading of rGO proliferates the reaction speed. This work, experimentally and theoretically, presents a new insight to enhance electrocatalytic urea oxidation reaction opening an avenue of urea-based energy-harvesting technology.

Mechanistic and Kinetic Analysis of Complete Methane Oxidation on a Practical PtPd/Al2O3 Catalyst

A PtPd/Al2O3 catalyst developed for the complete oxidation of methane from the ventilation air of underground coal mines is compared against a model PdO/Al2O3 catalyst. Although the PtPd/Al2O3 catalyst is substantially more active and stable than the model catalyst, the nature of active sites between the two catalysts is deemed to be fundamentally the same based on their response to different feed gas compositions and the evolution of surface CO adsorption complexes during time-resolved CO adsorption DRIFTS experiment. For both catalysts, coordinatively unsaturated Pd sites are considered the active centers for methane activation and the subsequent oxidation reaction. H2O competes with CH4 for the same active sites, resulting in severe inhibition. Additionally, the CH4 oxidation reaction also causes self-inhibition. Taking both inhibition effects into consideration, a relatively simple kinetic model is developed. The model provides a good fit of the 72 sets of kinetic data collected on the PtPd/Al2O3 catalyst under practically relevant reaction conditions with CH4 concentration in the range of 0.05–0.4%, H2O concentration of 1.0–5.0%, and reaction temperatures of 450–700 °C. Kinetic parameters based on the model suggest that the CH4 activation energy on the PtPd/Al2O3 catalyst is 96.7 kJ/mol, and the H2O adsorption energy is −31.0 kJ/mol. Both values are consistent with the parameters reported in the literature. The model can be used to develop catalyst sizing guidelines and be incorporated into the control algorithm of the catalytic system.

Mechanoluminescence driven by oxidation reactions in epoxy resins

The luminescence of two imidazole or anhydride cured epoxy resins has been investigated under the combined effect of mechanical stress and temperature using a special experimental setup developed for this purpose. Rupture and cyclic mechanical tests have been conducted in air and in nitrogen between room temperature and 110 °C. Luminescence was acquired through both temporal and spectral acquisitions. Light emission is observed only in air, and fits a Zhurkov model of bond scission. Spectral measurements show that adding a mechanical component to a thermal stress does not excite new molecular groups, indicating that degradation mechanisms under thermal stress or both thermal and mechanical stresses could be similar. A simple two-step model is proposed to describe luminescence as a combination of bond scission and light decay.

Nitrogen-doped CdS/TiO2 nanorods heterojunction photoanode for efficient and stable photoelectrochemical water splitting

Photoelectrochemical water splitting represents a promising route for converting solar energy into hydrogen, but sluggish reaction kinetics associated with inefficient charge separation and migration, and poor stability limit solar-to-hydrogen conversion. In this work, we develop a N-doped-CdS/TiO2-nanorods heterojunction photoanode for photoelectrochemical water splitting by anchoring CdS on TiO2 nanorods followed by nitrogen doping. The light harvesting is significantly enhanced and the charge separation and migration are promoted due to the formed heterojunction and nitrogen doping, which greatly enhances the water oxidation reaction. As a result, the photoelectrochemical cell with the optimized N-doped-CdS/TiO2-nanorods heterojunction photoanode yields a hydrogen production rate of 42.6 μmol cm−2 h−1, which is 2.51 times higher than that of the TiO2-nanorods photoanode. In particular, doping nitrogen atoms into CdS greatly alleviates the photocorrosion problem. Therefore, the newly-developed photoanode exhibits excellent stability under a continuous 10-h running.

A coumarin-based probe with far-red emission for the ratiometric detection of peroxynitrite in the mitochondria of living cells and mice

Peroxynitrite (ONOO−) is a transient and reactive oxidant with significant roles in numerous biological processes. Research has established a correlation between excessive mitochondrial ONOO− production and various diseases. As such we developed a mitochondria-targeting, fluorescence-based ratiometric probe using a boronate group for ONOO− recognition and coumarin as the fluorophore. The probe exhibited a 615 nm far-red emission, and a new fluorescence emission at 475 nm developed upon adding ONOO−.The probe possessed high sensitivity and selectivity for ONOO− detection with distinct ratiometric fluorescent output and a low detection limit of 11 nM. Significantly, Probe 1 could monitor ONOO− level fluctuations in biological systems due to its superior spectral properties and low toxicity. Notably, probe 1 has been effectively used for imaging in live HepG2 cells, zebrafish, Arabidopsis thaliana, and liver injury mouse tissues.

One-pot synthesis smartphone-assisted test strip based on food-grade Fe-β-Cyclodextrin nanozymes for rapid colorimetric analysis of ascorbic acid in foods and supplements

Accurate on-site analysis of food quality is of great significance for ensuring public health. Among them, ascorbic acid (AA) is an essential micronutrient widely used as an additive in juices and drugs to improve food quality and human health. In this work, we developed food-grade Fe-β-Cyclodextrin(Fe-β-CD) nanozymes based on inexpensive and readily available β-cyclodextrin and iron ions for the detection of AA. Fe-β-CD confirmed excellent peroxidase-like activity and oxidized colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to oxide TMB. AA could inhibit the oxidation reaction and cause blue to fade. Based on the above principles, Fe-β-CD nanozymes exhibited a low detection limit (3.4 μM) for detecting AA, with a wide linear range (10–300 μM). This method had been successfully used for the detection of AA in fruits and vitamin C tablets, and the results were consistent with the specified values. More importantly, an integrated smartphone-assisted Fe-β-CD@test strip colorimetric application platform constructed by one-pot method, the test strip also had better stability, and could be combined with smartphones to achieve convenient AA detection without using any instruments, which showed enormous potential for rapid and low-cost colorimetric detection of AA.

Ru-doped Aurivillius phase perovskites Bi4Ti3O12 for boosting photo-redox of N2 in photocatalytic nitrogen fixation

In this study, we prepared layered Aurivillius phase bismuth titanate perovskite oxide (Bi4Ti3O12, BT) using the sol–gel method and doped them with various amounts of Ru (BT-Rux, x = 0.05, 0.1, 0.25, and 0.5 % w/w) for photocatalytic nitrogen fixation in the absence of a sacrificial reagent. Among the prepared photocatalysts, BT-Ru0.25 showed the highest NH4+ formation rate of 119 μmolgcat−1 h−1, which is a 3.21-fold higher than BT. The Rietveld refinement X-ray diffraction results suggest that the expansion of the a and b lattice parameters of BT occurs with adding Ru, which correlates with the photocatalytic NH4+ production performance. This is because the expansion of a and b lattices of BT via Ru doping contributed to the increase in oxygen vacancies and the altered surface charge density in the Bi and Ti of BT, creating an asymmetric coordination environment that could induce the polarization of N2. Photoluminescence and Time-resolved photoluminescence analyses showed that the doping of Ru on BT reduced the recombination efficiency of the photogenerated electron-hole pairs and prolonged the electron decay time. In linear sweep voltammetry and Tafel analyses showed that Ru doping of BT suppressed the HER and photocorrosion. In-situ surfaced enhanced Raman spectroscopy (SERS) analysis revealed that the doping of Ru in BT improved the N2 interaction on the Bi-O bonds, accelerating the surface nitrogen oxidation reaction (NOR) to form NO3– and further undergoing a nitrate reduction reaction (NORR) for NH4+ production. This study highlights the importance of incorporating Ru into perovskite oxides to improve the separation of photogenerated carriers in photocatalytic NH4+ production without sacrificial reagents.

Highly active cobalt oxide-palladium nanohybrid catalyst enables selective electrocatalytic synthesis of glycolic acid

Glycolic acid is a unique value-added chemical, while its large-scale production is limited by harsh synthesis conditions and poor selectivity. Herein, we have ingeniously constructed a highly active cobalt oxide-supported palladium electrocatalyst on nickel foam (Pd-Co3O4/NF) for ethylene glycol oxidation to glycolic acid with a high Faradaic efficiency (93.1 %) at ultra-low potential (0.9 V vs. RHE). In situ Fourier transform infrared spectroscopy revealed the pathway of ethylene glycol oxidation reaction (EGOR). The theoretical results reveal that Co3O4/NF can effectively promote the formation of *OH and weaken the adsorption of toxic *CO intermediates on Pd-Co3O4/NF. And the downshifted d-band center of Pd-Co3O4/NF is inducive to facilitate the desorption of GA from the Pd surface, prevents the excessive oxidation thus improving the selectivity. Moreover, Pd-Co3O4/NF exhibits considerable anode current density with respect to electro-reforming polyethylene terephthalate (PET)-derived EG oxidation, accompanied by the generation of green hydrogen at the cathode. This work puts forward an innovative approach for catalyst construction toward EGOR and highlights the strategy of electro-upcycling of PET.