Hydrogen Radicals Research Articles

Peroxymonosulfate activation by suspended biogenic manganese oxides for polishing micropollutants in wastewater effluent

The activation of peroxymonosulfate (PMS) to generate radical oxygen species (ROS) for in situ chemical oxidation has been shown to be an efficient technology for polishing micropollutants in wastewater effluent. Thus, it is also of great importance to develop environmental-friendly catalysts for PMS activation. The present study employed suspended biogenic manganese oxides (BioMnOx) to activate PMS for the efficient micropollutant removal. In a feasibility test, relatively high removal efficiencies (>80 %) of 14 selected micropollutants were obtained over short reaction times (20 min), in particular for refractory micropollutants such as carbamazepine (98 %), diclofenac (100 %) and metoprolol (81 %). The inhibition effect of coexisting anions to PMS activation was also investigated, which showed that the addition of HCO3– inhibited this process, while the addition of Cl– showed negligible effect. Based on radical quenching experiments, sulfate radical, hydrogen radical and singlet oxygen were all involved in the PMS activation process, while the responsible ROS for micropollutants removal were compound-specific. Furthermore, a novel BioMnOx/PMS system was established by utilising BioMnOx-coated carriers as catalyst, which were obtained from a previously engineered moving bed biofilm reactor (MBBR). This special BioMnOx/PMS system was then applied as an effluent polishing step. Results showed that most micropollutants were efficiently removed through the BioMnOx/PMS system, such as diclofenac (91 %) and sulfamethoxazole (98 %). Lastly, the toxicity of the MBBR effluent was determined by Vibrio fisheri, which showed minimum toxic effect after the polishing treatment.

Chemical Composition and Biological Activities of the Leaf Essential Oils of Curcuma longa, Curcuma aromatica and Curcuma angustifolia.

Curcuma species are widely used as a food additive and also in various medicinal purposes. The plant is a rich source of essential oil and is predominantly extracted from the rhizomes. On the other hand, the leaves of the plants are usually considered as an agrowaste. The valorization of these Curcuma leaf wastes into essential oils is becoming accepted globally. In the present study, we aim to extract essential oils from the leaves of Curcuma longa (LEO), C. aromatica (REO), and C. anguistifolia (NEO). The chemical composition of these essential oils was analyzed by GC-MS. Free radical scavenging properties were evaluated against the radical sources, including DPPH, ABTS, and hydrogen peroxide. The antibacterial activity was assessed by the disc diffusion method and Minimum inhibitory concentration analysis against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica) bacteria. Results identified the compounds α-phellandrene, 2-carene, and eucalyptol as predominant in LEO. The REO was predominated by camphor, 2-bornanone, and curdione. The main components detected in NEO were eucalyptol, curzerenone, α-lemenone, longiverbenone, and α-curcumene. Antioxidant properties were higher in the LEO with IC50 values of 8.62 ± 0.18, 9.21 ± 0.29, and 4.35 ± 0.16 µg/mL, against DPPH, ABTS, and hydrogen peroxide radicals. The cytotoxic activity was also evident against breast cancer cell lines MCF-7 and MDA-MB-231 cells; the LEO was found to be the most active against these two cell lines (IC50 values of 40.74 ± 2.19 and 45.17 ± 2.36 µg/mL). Likewise, the results indicated a higher antibacterial activity for Curcuma longa essential oil with respective IC50 values (20.6 ± 0.3, 22.2 ± 0.3, 20.4 ± 0.2, and 17.6 ± 0.2 mm). Hence, the present study confirms the possible utility of leaf agrowastes of different Curcuma spp. as a possible source of essential oils with pharmacological potential.

Response Surface Optimization for Investigating Antioxidant Potential of Camellia Sinensis and Withania Somnifera in Synergistic Manner.

The online version contains supplementary material available at 10.1007/s40011-022-01423-6.

Computational screening of nonmetal dopants to active MoS2 basal-plane for hydrogen evolution reaction via structural descriptor

Nonmetal doping is an efficient approach to activate inert MoS2 basal plane, which converts MoS2 into an electrocatalyst for the hydrogen evolution reaction (HER). However, the trial-and-error approach through experimental attempt is still a common practice to search for suitable nonmetal dopants. In this work, we employ density functional theory (DFT) and microkinetic model to assess alkaline HER activity of nonmetal-modified MoS2(001), which show strong variation in the degree of activation by single- or double-dopants across nonmetal element series (B, C, N, P, O, S, Se and Te). To assist the screening of nonmetal dopants to active MoS2 basal plane, a structural descriptor-based prediction model is constructed. It demonstrates that the activation effect of nonmetal dopant is achieved through the adjustment of valence electron occupancy of reaction center, which tunes the adsorption energy of atomic hydrogen and hydroxide radical, and accordingly reaction kinetic for alkaline HER. The structural descriptor-based prediction model reproduce the activity trend among non-metallic doped MoS2 from available experimental references. In addition, we screened out MoS2 modified by BTe and BSe double dopants with lower overpotential than reported nonmetal-modified MoS2 systems. This work gives a deep insight into activation mechanism of nonmetal dopant for MoS2, and provides an efficient screening strategy for future catalyst design of transition metal dichalcogenides.

Modelling of hydrogen-blended dual-fuel combustion using flamelet-generated manifold and preferential diffusion effects

In the present study, Reynolds-Averaged Navier-Stokes simulations together with a novel flamelet generated manifold (FGM) hybrid combustion model incorporating preferential diffusion effects is utilised for the investigation of a hydrogen-blended diesel-hydrogen dual-fuel engine combustion process with high hydrogen energy share. The FGM hybrid combustion model was developed by coupling laminar flamelet databases obtained from diffusion flamelets and premixed flamelets. The model employed three control variables, namely, mixture fraction, reaction progress variable and enthalpy. The preferential diffusion effects were included in the laminar flamelet calculations and in the diffusion terms in the transport equations of the control variables. The resulting model is then validated against an experimental diesel-hydrogen dual-fuel combustion engine. The results show that the FGM hybrid combustion model incorporating preferential diffusion effects in the flame chemistry and transport equations yields better predictions with good accuracy for the in-cylinder characteristics. The inclusion of preferential diffusion effects in the flame chemistry and transport equations was found to predict well several characteristics of the diesel-hydrogen dual-fuel combustion process: 1) ignition delay, 2) start and end of combustion, 3) faster flame propagation and quicker burning rate of hydrogen, 4) high temperature combustion due to highly reactive nature of hydrogen radicals, 5) peak values of the heat release rate due to high temperature combustion of the partially premixed pilot fuel spray with entrained hydrogen/air and then background hydrogen-air premixed mixture. The comparison between diesel-hydrogen dual-fuel combustion and diesel only combustion shows early start of combustion, longer ignition delay time, higher flame temperature and NOx emissions for dual-fuel combustion compared to diesel only combustion.

Tetracycline degradation by nonthermal plasma: removal efficiency, degradation pathway, and toxicity evaluation.

Tetracyclines (TCs) are often discussed as one of the emerging contaminants detected in water matrices and studied for their persistence towards conventional water treatment technologies. In this work, the treatment of TC in aqueous solutions with nonthermal plasma gliding arc process was investigated. The degradation efficiency of TC was studied along with the effect of initial concentration, working gas, pH, and the presence of a radical scavenger. The generation of reactive oxidative species was characterized by the quantification of radical hydroxyl, hydrogen peroxide, ozone, nitrite, and nitrate. Mineralization efficiency was examined by assessment of Total organic carbon evolution. Experimental results have shown that the gliding arc plasma is effective for the treatment of TC. At an initial concentration of 5 mg/L: degradation rates of 94.95% and 60.45% were achieved, while mineralization rates were 81.3% and 57.34% under O2 and air plasma, respectively. O2 plasma exhibited an immense potential for the generation of reactive oxygen species. Meanwhile, air plasma showed better degradation performance in the presence of a radical scavenger. Moreover, degradation products were identified by mass spectroscopy analysis and degradation pathway was proposed. The gliding arc process proposed in this work is promising for the removal of TC antibiotics.

MRI of radiation chemistry: First images and investigation of potential mechanisms.

Paramagnetic species such as O2 and free radicals can enhance T1 and T2 relaxation times. If the change in relaxation time is sufficiently large, the contrast will be generated in magnetic resonance images. Since radiation is known to be capable of altering the concentration of O2 and free radicals during water radiolysis, it may be possible for radiation to induce MR signal change. We present the first reported instance of x-ray-induced MR signal changes in water phantoms and investigate potential paramagnetic relaxation enhancement mechanisms associated with radiation chemistry changes in oxygen and free radical concentrations. Images of water and 10 mM coumarin phantoms were acquired on a 0.35 T MR-linac before, during, and after a dose delivery of 80Gy using an inversion-recovery dual-echo sequence with water nullified. Radiation chemistry simulations of these conditions were performed to calculate changes in oxygen and free radical concentrations. Published relaxivity values were then applied to calculate the resulting T1 change, and analytical MR signal equations were used to calculate the associated signal change. Compared to pre-irradiation reference images, water phantom images taken during and after irradiation showed little to no change, while coumarin phantom images showed a small signal loss in the irradiated region with a contrast-to-noise ratio (CNR) of 1.0-2.5. Radiation chemistry simulations found oxygen depletion of -11µM in water and -31µM in coumarin, resulting in a T1 lengthening of 24ms and 68ms respectively, and a simulated CNR of 1.0 and 2.8 respectively. This change was consistent with observations in both direction and magnitude. Steady-state superoxide, hydroxyl, hydroperoxyl, and hydrogen radical concentrations were found to contribute less than 1ms of T1 change. Observed radiation-induced MR signal changes were dominated by an oxygen depletion mechanism. Free radicals were concluded to play a minor secondary role under steady-state conditions. Future applications may include in vivo FLASH treatment verification but would require an MR sequence with a better signal-to-noise ratio and higher temporal resolution than the one used in this study.

Exploring the kinetics and mechanism of C2F5C(O)CF(CF3)2 reaction with hydrogen radical

This work combined high-level quantum chemistry calculations with RRKM/master-equation simulations to gain insight into reactions between C6F12O and hydrogen radical under combustion conditions. The energetics for all stationary points on potential energy surface were determined at CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) level of theory. RRKM/master-equation calculations were utilized to simulate the title reaction over a wide range of temperatures and pressures, i.e. 300–3000 K and 0.01–100 atm. Kinetic and mechanistic analyses demonstrate that hydrogen addition to initial adduct C2F5CFCOH(CF3)2 and two dissociations from adduct (CF3)2CFCHOC2F5 to CF3CF2COH + CF3CFCF3 and (CF3)2CFCOH) + CF3CF2 conjointly dominate the overall kinetics over the investigated temperatures and pressures.

Search for the Decomposition Process of 2,4,6-Trinitrotoluene by an Evolutionary Algorithm.

In this paper, we explored stable states in the system of 2,4,6-trinitrotoluene (TNT) crystal with a few additional hydrogen radicals (Hadd's) using a structure-search scheme based on first-principles calculations and an evolutionary algorithm (EA) to get insights into the decomposition process of TNT. We introduced three evolutionary operators acting on Hadd's and transforming only local structures of TNT molecules: "displacement", "permutation", and "mating". We searched for stable structures by increasing the number of Hadd's (n) from 1 to 2, 3, 4, 6, and 8 and constructed a convex-hull diagram for the formation energy from solid TNT and solid hydrogen. We showed that the system of n = 6 had the largest energy reduction, in which five of the eight TNT molecules in the calculation cell were transformed into NO, H2O, C2H3N, C2NO3H3, C8N2O4H7, C9N2O8H5, and C14N7O12H11. Analysis of the structural transformations observed during the EA search indicates that (1) the Hadd's approaching the TNT molecules react with C, forming a six-membered ring, and with N and O in nitro groups, leaving the TNT molecules as NO, H2O, C2H3N, and C2NO3H3, and (2) the partially decomposed TNT molecules are bonded to one another via C, N, and O.

One-pot H/D exchange and low-coordinated iron electrocatalyzed deuteration of nitriles in D2O to α,β-deuterio aryl ethylamines

Developing a step-economical approach for efficient synthesis of α,β-deuterio aryl ethylamines (α,β-DAEAs) with high deuterium ratios using an easy-to-handle deuterated source under ambient conditions is highly desirable. Here we report a room-temperature one-pot two-step transformation of aryl acetonitriles to α,β-DAEAs with up to 92% isolated yield and 99% α,β-deuterium ratios using D2O as a deuterium source. The process involves a fast α-C − H/C − D exchange and tandem electroreductive deuteration of C ≡ N over an in situ formed low-coordinated Fe nanoparticle cathode. The moderate adsorptions of nitriles/imine intermediates and the promoted formation of active hydrogen (H*) on unsaturated Fe sites facilitate the electroreduction process. In situ Raman confirms co-adsorption of aryl rings and the C ≡ N group on the Fe surface. A proposed H*-addition pathway is confirmed by the detected hydrogen and carbon radicals. Wide substrate scope, parallel synthesis of multiple α,β-DAEAs, and successful preparation of α,β-deuterated Melatonin and Komavine highlight the potential.

Mathematical Models of the Generation of Radiation-induced DNA Double-strand Breaks and Misrepair Cells by Direct and Indirect Action

Free radical carries an unpaired electron in the outer shell which is very reactive and becomes toxic to DNA. The direct action hits cell directly, while indirect action is the interaction between ionizing radiation and water molecule which later produces free radical. Hydrated electron (e), hydroxyl radical (OH), hydrogen radical (OH), ionized water, hydroperoxyl radical and hydrogen peroxide are examples of free radical products. Among of these three free radicals, DNA damage dominantly caused by hydroxyl radical (OH) because it is found to be highly reactive compared to others. This paper aimed to develop a model by using structured population dynamics approach to study the effects of ionizing radiation by direct and indirect actions. The effects of ionizing radiation are mathematically described in a model using Ordinary Differential Equations (ODEs). The simulation results are fitted to the Linear Quadratic (LQ) formulation to give the ratio for alpha/beta . Next, the parameter estimation of the model is carried out using experimental data of human colon carcinoma cell by the aid of the MATLAB programming. The estimated parameter values can explain the biological meaning, which can support the result of the experimental design. The result showed that the sum-squared error (SSE) between simulation data and experimental data obtained is 0.0019 which indicates an excellent t to the experimental data. Thus, the model developed is in line with the experimental result. The model is able to explain the dynamics process of the direct and indirect effect of ionizing radiation on the cell population.

Molecular-based asphalt oxidation reaction mechanism and aging resistance optimization strategies based on quantum chemistry

Understanding the oxidation reaction mechanism of asphalt is critical to improving its aging resistance. Here, quantum chemistry (QC) was used to study the oxidation reaction mechanism of 12 typical asphalt molecules. On this basis, the molecular models of aged asphalt were established, and the aging resistance optimization strategies of asphalt were proposed. The results show that the oxidation sites for oxygen-containing or heteroatoms-free molecules are on aromatic carbons (I molecules). Reducing hydrogen and hydroxyl radicals can improve its aging resistance. The oxidation sites for sulfur- or nitrogen-containing molecules are on heteroatoms (II molecules). Reducing oxygen free radicals content can improve its aging resistance. The molecules containing sulfur and cata-condensed polycyclic aromatic hydrocarbons (PAHs) (such as R5) have the strongest oxidation reactivity. Reducing its content can improve asphalt aging resistance. Combining the QC and experiment results, LH90 contains more I molecules, while UP70 and MM70 contain more II molecules (especially As3 and R5). The aging resistance of UP70 and MM70 is poor than LH90. Reducing the content of As3 or R5 molecules or the content of oxygen radicals can improve the aging resistance of UP70 and MM70. These findings lay a foundation for designing and preparing asphalt with excellent aging resistance.

σ-Alkynyl Adsorption Enables Electrocatalytic Semihydrogenation of Terminal Alkynes with Easy-Reducible/Passivated Groups over Amorphous PdSx Nanocapsules.

Highly chemo- and regioselective semihydrogenation of alkynes is significant and challenging for the synthesis of functionalized alkenes. Here, a sequential self-template method is used to synthesize amorphous palladium sulfide nanocapsules (PdSx ANCs), which enables electrocatalytic semihydrogenation of terminal alkynes in H2O with excellent tolerance to easily reducible groups (e.g., C-I/Br/Cl, C═O) and the metal center deactivating skeletons (e.g., quinolyl, carboxyl, and nitrile). Mechanistic studies demonstrate that specific σ-alkynyl adsorption via terminal carbon and negligible alkene adsorption on isolated Pd2+ sites ensure successful synthesis of various alkenes with outstanding time-irrelevant selectivity in a wide potential range. The key hydrogen and carbon radical intermediates are validated by electron paramagnetic resonance and high-resolution mass spectrometry. Gram-scale synthesis of 4-bromostyrene and expedient preparation of deuterated alkene precursors and drugs with D2O show promising applications. Impressively, PdSx ANCs can be applied to the prevailing thermocatalytic semihydrogenation of functionalized alkyne using H2.

Antioxidant activity of caffeic acid: thermodynamic and kinetic aspects on the oxidative degradation pathway

Caffeic acid is a phenolic secondary metabolite from plants, which is known for its antioxidant properties. The effective mitigation of methanol-induced oxidative stress by caffeic acid depends on the direct radical scavenging as well as the formation of new metabolites via oxidative degradation. Herein, thermodynamic and kinetic aspects of the oxidative degradation pathway of caffeic acid in the presence of radical CH3O• and its isomer, •CH2OH are discussed for the first time, employing density functional theory (DFT). The direct radical scavenging activity of caffeic acid against these radicals is verified via hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms. HAT is predicted to be more feasible than RAF mechanism as per the computed data. Additionally, energetic details of the proposed oxidative degradation pathway of radical adduct intermediates toward the formation of a cyclic metabolite is analyzed. Kinetic studies indicated a significant tunneling contribution to the H abstraction pathways having high activation barriers. Further, our results imply that the newly formed metabolites exhibit comparable antioxidant activity with that of caffeic acid.

Effectiveness of flame suppressants on cool flames and hot flames

While the effectiveness of various flame suppressants such as bromotrifluoromethane and trimethylphosphate on hot flames has been relatively well studied over the years, such suppressants have not been examined in the context of low-temperature cool flames. This investigation solves this issue by exploring the extinction limits of six suppressants on both hot flames and cool flames in the counterflow geometry using n-dodecane as the fuel. In contrast to hot flames, it is found both experimentally and numerically that cool flames are relatively impervious to chemically based suppressants such as bromotrifluoromethane; these suppressants are essentially diluents at low temperatures. Detailed examination of the computed flame structure reveals that the reactions composing the catalytic cycles that interfere with hydrogen radical and hydroxyl radical production in hot flames are orders of magnitude lower in cool flames. Furthermore, mildly flammable suppressants such as trimethylphosphate and 2‑bromo-3,3,3-trifluoropropene are observed to ignite under the conditions necessary to initiate cool flames, which limits measurements of the cool flame extinction limits. This premature oxidation is not predicted by kinetic models describing the suppressant chemistry.

Evaluation of Bioactive Secondary Metabolites from Ponyfish Associated Bacteria (<i>Photobacterium leiognathi</i>)

The marine environment continues to surprise us by producing novel bioactive substances with a wide range of benefits for humans. Materials and Methods: Marine bioluminescent bacteria Photobacterium leiognathi was isolated from pony fish, Secutorruconius which was confirmed with microscopic and molecular characterization. The secondary metabolite of the isolated bacteria was extracted with dichloromethane. The chemical fingerprinting of the isolated metabolite was analyzed through TLC, FT-IR, and HPLC. The nature of the compound present in the metabolite was identified in the gas chromatography-mass spectrometry analysis (GC - MS). The isolated extract was investigated for its antibacterial property against 10 human pathogenic bacteria and also its antioxidant activity using different assays such as 1, 1-Diphenyl-2-picrylhydrazyl, Phosphomolybdenum, Metal chelating, Hydroxyl radical scavenging and hydrogen peroxide scavenging activity. Results: The Presence of functional groups including phenols, sugars, and amino acids in the extracts were identified by TLC. Totally, nine peaks were obtained for the crude extract through the FTIR spectrum range of 400 to 4000 cm-1 for the active sample. The DCM extract showed a broad spectrum of antibacterial activity against the six human bacterial pathogens. Secondary metabolites from the bioluminescent bacteria, P. leiognathi, have strong antioxidant properties. These results will be instrumental in developing novel products with biosensors and bio-imaging applications using P. leiognathi.

Insight into the pyrolysis behavior of polyvinyl chloride using in situ pyrolysis time-of-flight mass spectrometry: Aromatization mechanism and Cl evolution

Online characterization of primary volatiles is crucial for a better understanding of the aromatization mechanism and interaction between radical intermediates triggered by chlorine (Cl) evolution in pyrolysis of polyvinyl chloride (PVC). In this study, in situ pyrolysis time-of-flight mass spectrometry (in situ Py-TOF-MS) equipped with double ionization sources, vacuum ultraviolet photoionization (VUVPI, 10.6 eV), and electron ionization (EI, 70 eV) was applied to online capture primary volatiles released from PVC pyrolysis. According to the total ion currents of primary volatiles with temperature, the pyrolysis of PVC is divided into two stages: stage I (40–343 °C) and stage II (343–650 °C). The results indicated that benzene is the most abundant product that is formed through cyclization/aromatization of long-chain hydrocarbon radicals (LCRs) triggered by dechlorination in stage I, while naphthalene can be formed from interactions of cyclopentadienyls released by LCR cyclization/aromatization. Meanwhile, the hydrogen radicals (H·) extracted from the CH bonds will transfer and react with chlorine radicals (Cl·) to promote HCl release. Aromatics are also released in stage II, among which monoaromatic hydrocarbons (MAHs) are generated by cyclization of fragment-radicals and Diels-Alder (D-A) reactions, while polycyclic aromatic hydrocarbons (PAHs) are formed by cyclization/aromatization and rearrangement reactions. Simultaneously, the Cl-containing long-chain hydrocarbon radicals can fracture to form short-chain Cl-aliphatics as the temperature rises and can also be cyclized/aromatized to form Cl-MAHs. Additionally, other formation pathways, such as the interaction of released Cl· and aliphatic radicals to form Cl-aliphatics and the D-A reaction between dienes and Cl-aliphatics to form Cl-MAHs, were also found.

Mechanism of aliphatic hydrogen on the caking property of 1/3 coking coal during rapid preheating

It is of significance to reveal the mechanism of rapid preheating to enhance the caking property of coking coal and expand high-quality coking coal resources. In this study, a 1/3 coking coal was preheated at two low and one rapid rates, then raw coal and heat-treated samples were comprehensively analyzed. The results revealed that the aliphatic H in coal formed volatiles at the early stage of pyrolysis (≤ 380 °C) under low-rate preheating. In the thermoplastic stage, the bonding phase was confirmed to be formed by a part of aliphatic H. The decreases amount of volatile and hydrogen contents and H/C and O/C atomic ratios of rapidly preheated coals were less than those of low-rate preheated coals, indicating that its thermal decomposition reaction degree was lower. This was considered to be the basis for keeping G values of rapidly preheated coals from decreasing. The aliphatic H concentration and CH2/CH3 ratios of rapidly preheated coals were higher and lower than those of raw coal respectively, which contributed to the fact that their G values were basically close to or higher (∼349–401 °C) than that of raw coal. Rapid preheating weakened the consumption of aliphatic H by volatiles formed during low-rate heating. Moreover, it forced weak bonds in the molecular of coal to break, such as bridge bonds and intermolecular forces that connect structural units. The breaking of bridge bonds between alkyl side chains or cycloalkanes and aromatic groups enhanced hydrogen supply. The weakening of intermolecular force resulted in loose macromolecular network structure and enhanced molecular dynamic properties. These evolutions of coal molecular structure strengthened the combination of hydrogen and free radicals and generated more bonding phases. Finally, a mechanism which provided a new explanation for the rapid preheating to alter the molecules structure and enhance the caking property of coking coal was proposed, and it will be significant valuable to enlarge the utilization of weakly-caking coal in coking process.

Tin removal by an annular surface wave plasma antenna in an extreme ultraviolet lithography source

Tin contamination of the collector mirror surface remains one of the crucial issues of EUV (Extreme Ultraviolet) sources, directly impacting the availability of the tool. Hydrogen plasma-based tin removal processes employ hydrogen radicals and ions to interact with tin deposits to form gaseous tin hydride (SnH4), which can be removed through pumping. An annular surface wave plasma (SWP) source developed at the University of Illinois—Urbana Champaign is integrated into the cone and perimeter of the collection mirror for in situ tin removal. The SWP is characterized by high ion and radical densities, low electron temperature, and local generation where etching is needed. This method has the potential to significantly reduce downtime and increase mirror lifetime. Radical probe measurements show hydrogen radical densities in the order of 1019 m−3, while Langmuir probe measurements show electron temperatures of up to 6 eV and plasma densities on the order of 1017–18 m−3. The generated ions are essential to the tin cleaning and have sufficiently low energy to cause no damage to the collector capping layer. Tin etch rates of up to 270 nm/min were observed in a variety of experimental conditions, including various powers, pressures, flowrates, and temperatures. The high etch rates demonstrated in this study exceed the expected contamination rate of the EUV source.

Electronic Metal-Support Interaction Triggering Interfacial Charge Polarization over CuPd/N-Doped-C Nanohybrids Drives Selectively Electrocatalytic Conversion of Nitrate to Ammonia.

Selective electrocatalytic nitrate-to-ammonia conversion holds significant potential in treatment of nitrate wastewater and simultaneously produces high-value-added ammonia. However, today's development of nitrate-to-ammonia technology remains hindered by the lack of electrocatalysts with high activity and selectivity. In this work, metal-organic framework-derived CuPd bimetallic nanoparticles/nitrogen-doped carbon (CuPd/CN) hybrid nanoarrays for efficient ammonia electrosynthesis from nitrate are designed and synthesized. Systematic characterization reveals that the electronic metal-support interaction between the CuPd nanoparticles and N-doped nanocarbon matrix could trigger interfacial charge polarization over the CuPd/CN composite and make Cu sites electron deficient, which is conducive to the adsorption of nitrate ions. Moreover, the Pd atom sites separate by Cu atoms and could catalyze the dissociation of H2 O molecules to form adsorbed H species, which evolves into hydrogen radicals and behaves as the dominant reactive species in accelerating nitrate-to-ammonia electrocatalysis. These advantages endow the CuPd/CN nanoarrays with high faradaic efficiency (96.16%), selectivity (92.08%) as well as excellent catalytic stability for electroreduction of nitrate to ammonia.