Nanoscience and nanotechnology have been undergoing the most explosive growth. However, well-controlled synthesis for manufacturing nanostructures still remains a challenge. In this work, we report a ...facile procedure to successively prepare the molybdenum dioxide (MoO
2
), molybdenum carbide (Mo
2
C) and molybdenum disulfide (MoS
2
) nanodots on carbon nanotubes (CNT). The prepared samples all possess super fine size. The electrocatalytic properties towards hydrogen evolution reaction (HER) of the three samples are investigated. The results indicate that the MoO
2
/CNT sample still exhibits very poor HER property, with 420 mV to drive a current density of 10 mA cm
−2
, while the Mo
2
C/CNT and MoS
2
/CNT samples show highly efficient HER performance, requiring overpotentials of 103 mV and 134 mV to accomplish the same current density, respectively. This work provides a very simple method for preparation of Mo-based nanodot catalysts which can be easily promoted for large-scale production.
Graphical Abstract
The MoO2, Mo2C and MoS2 nanodots are successively prepared on CNT by a facile procedure. The MoO2/CNT sample exhibits very poor HER property, while the Mo2C/CNT and MoS2/CNT samples show highly efficient HER performance.
•Fenton in € m−3 g-TOC−1 (% mineralization): 102 (50%), 419 (75%), 937 (99%)•Electro-Fenton in € m−3 g-TOC−1 (% mineralization): 108 (50%), 117 (75%), 125 (99%)•Photo-Fenton in € m−3 g-TOC−1 (% ...mineralization): 161 (50%), 196 (75%), 616 (99%)•Ozonation in € m−3 g-TOC−1 (% mineralization): 966 (50%), 1279 (75%), 3203 (99%)•O2-equivalent dose (kg-O2 at 50%): 0.0004 (EF) < 0.0013 (Fenton) < 0.0045 (O3)
Advanced oxidation processes (AOPs) have received a lot of attention over the years as advanced physico-chemical polishing wastewater treatments to remove biorefractory pollutants. Additionally, many studies report their excellent degradation and mineralization performance as stand-alone technologies too, demonstrating the versatility of these processes; however, there is a lack of suitable methods to compare the performance (in terms of removal efficiency and operating costs) of different AOPs in the same conditions. In this context, the goal of this paper is to propose a systematic investigation by introducing a novel criterion, namely the accumulated oxygen-equivalent chemical-oxidation dose (AOCD), to systematically compare the diverse AOPs available: ozonation, H2O2 photolysis, Fenton, photo-Fenton, electro-Fenton and photoelectro-Fenton (paired with anodic oxidation, for the latter two). For each of these, the cost efficiency was determined by optimizing the operating conditions for the removal of phenol, selected as a model pollutant (1.4 mM, equivalent to 100 mg-C L−1). The operating costs considered sludge management, chemical use and electricity consumption. Among all AOPs, electro-Fenton was the most cost-effective (108 - 125 € m−3), notwithstanding the mineralization target (50%, 75% and 99%), owing to its electrocatalytic behavior. Chemical Fenton proved competitive too up to 50% of mineralization, meaning that it could also be considered as a cost-effective pre-treatment solution. AOCD was the lowest for electro-Fenton, which could be attributed to its excellent faradaic yield, while UV-based processes generally required the highest dose. The AOCD criterion could serve as a baseline for AOP comparison and prove useful for the legislator to determine the “best available techniques” as defined by the Industrial Emissions European Union Directive 2010/75/EU.
Display omitted
Whither the oxide interface Chakhalian, J; Millis, A J; Rondinelli, J
Nature materials,
02/2012, Volume:
11, Issue:
2
Journal Article
Peer reviewed
Interfaces formed by transition-metal oxide materials offer a tremendous opportunity for fundamental as well as applied research. Yet, as exciting as these opportunities are, several challenges ...remain. Oxide heterostructures present a tremendous opportunity for realizing new phases through controlled synthetic routes. Taking advantage of these opportunities raises challenges for theory, for synthesis and for measurements. The structure-property relationships, which will continue to emerge from this understanding, are likely to be used by electrical and chemical engineers for the design of wholly new electronic architectures and green-energy technologies.
The removal and degradation of refractory antibiotics in saline water by electrochemical and photo-electrochemical catalysis has emerged as a worldwide research hotspot. Aiming to improve degradation ...performance, most of the concerned studies focus on new sophisticated materials and modification methods on the single working electrode (anode or cathode). But the synergistic effects between anode and cathode has rarely been studied, especially in photo-electrochemical system. In this work, these effects were initially developed and investigated in the photo-electrochemical system. In this work, a low-cost double-working electrodes photo-electrochemical system (TSSC-Photo) with Ti/SnO2-Sb anode and carbon black air diffusion cathode (TSSC) was constructed for Norfloxacin (NOR) degradation in saline water. The degradation efficiency, vital factors, degradation pathways were investigated. The mathematic modeling was adopted to distinguish the degradation kinetics and degradation contributions ratio from anode and cathode sides of this system. Owing to the synergistic effects of both electrodes, a rapidly complete NOR removal was achieved within 4 min and the highest TOC removal ratio reached 83.9% within 120 min. Free radicals (•Cl, •OH, etc) were considered as dominate oxidants in degradation with no activated chlorine (HClO/ClO−) detected from the electrolyte during the photo-electrolysis. The analysis based on the mathematic modeling indicated that anode acted as the only contributor (>97% of overall contribution) during the first 5 min of photo-electrolysis, whereas at the end of 120 min running, 21.4% of the total contribution came from cathode side. The remarkable performance of TSSC-Photo claimed its great capacity for organic matter degradation in saline water especially with Cl−.
Display omitted
•A novel efficient, clean and low-cost photo-electro-catalysis method was designed.•Higher degradation performance compared with other photo or electro methods.•Oxalic acid was smallest intermediate, and secondary pollution can be ignored.•Cathode’s contribution ratio on degradation rises in longer running time.•The novel method showed potential for organic matter degradation in saline water.
•Thermodynamic basics of MEC are revisited.•Equilibrium cell voltage of 0.123 V and maximum energy yield of 10 are main advantages.•Faradaic yields can help identifying various MEC ...malfunctioning.•Adding salts to increase the electrolyte ionic conductivity exacerbates pH issues.•Local pH gradients and ion migration form a negative feedback loop.
Microbial electrolysis cells (MECs) produce hydrogen at the cathode associated with the oxidation of organic matter at the anode. This technology can produce hydrogen by consuming less electrical energy than water electrolysis does. However, it has been very difficult so far to scale up efficient MECs beyond the size of small laboratory cells.
This article firstly revisits the fundamentals of MECs to assert their theoretical advantages. The low formal equilibrium cell voltage of 0.123 V and electrical and thermal energy yields as high as 10 and 12, respectively, are major assets. Other theoretical strengths are discussed, including the possibility to produce methane, and some safety advantages.
The experimental achievements at pilot scale (several litres volume) are analysed through the prism of electrochemical engineering. This analysis leads to recommendations to modify some research efforts, notably by giving priority to increasing current density rather than working with volumetric parameters, using Faradaic yields to detect dysfunctions, and systematizing control experiments at open circuit. The critical analysis successively addresses electrolytes, electrode kinetics, temperature, substrate concentration, reactor architecture, and control procedures. It brings to light intrinsic weaknesses of the MEC concept and identifies improvements that can be made using current technology, for instance, by the catalysis of hydrogen evolution at neutral pH. The problem of the low electrolyte conductivity is pointed out and, in return, how increasing it can be detrimental to the key issue of anode acidification. Finally, research lines are proposed with the objective of moving ahead towards MEC development.
Posttranscriptional tRNA modifications are essential for proper gene expression, and defects in the enzymes that perform tRNA modifications are associated with numerous human disorders. Throughout ...eukaryotes, 2′-O-methylation of residues 32 and 34 of the anticodon loop of tRNA is important for proper translation, and in humans, a lack of these modifications results in non-syndromic X-linked intellectual disability. In yeast, the methyltransferase Trm7 forms a complex with Trm732 to 2′-O-methylate tRNA residue 32 and with Trm734 to 2′-O-methylate tRNA residue 34. Trm732 and Trm734 are required for the methylation activity of Trm7, but the role of these auxiliary proteins is not clear. Additionally, Trm732 and Trm734 homologs are implicated in biological processes not directly related to translation, suggesting that these proteins may have additional cellular functions. To identify critical amino acids in Trm732, we generated variants and tested their ability to function in yeast cells. We identified a conserved RRSAGLP motif in the conserved DUF2428 domain of Trm732 that is required for tRNA modification activity by both yeast Trm732 and its human homolog, THADA. The identification of Trm732 variants that lack tRNA modification activity will help to determine if other biological functions ascribed to Trm732 and THADA are directly due to tRNA modification or to secondary effects due to other functions of these proteins.
The present study is dedicated to the development of experimental procedures allowing the measurement of the individual heats of adsorption of adsorbed NH3 species on a sulfate-free TiO2 solid (P25 ...from Degussa). This solid has been selected because it is frequently used as support of V2O5- or/and WO3-TiO2 model catalysts for the understanding of the surface processes implicated in the selective catalytic reduction of NOx by NH3 (NH3-SCR). Two original analytical procedures denoted adsorption equilibrium infrared spectroscopy (AEIR) and temperature-programmed adsorption equilibrium (TPAE) (developed in previous works) were applied. These methods are based on (a) the experimental measurement of the change in the adsorption equilibrium coverage of the individual adsorbed species in isobar conditions and (b) the comparison of the experimental data to an adsorption model. It is shown that in the ranges of the ammonia partial pressures and reaction temperatures of the NH3-SCR process, only two adsorbed NH3 species on Lewis sites (Ti+delta) are detected on the solid dehydrated at 673 K. These species noted NH3ads.L1 and NH3ads.L2 are differentiated by their delta(s) NH3 IR bands at 300 K (1149 and 1228 cm(-1), respectively), whereas their delta(as) IR bands are at the same position (1596 cm(-1)). The AEIR and TPAE methods indicate that the heats of adsorption of the NH3ads.L1 and NH3ads-L2 species (noted E-L1(theta) and EL2(theta) accuracy +/- 5 kJ/mol) vary linearly with their respective coverages theta from E-L1(1) = 56 kJ/mol to E-L1(0) = 105 kJ/mol and from E-L2(1) = 105 kJ/mol to E-L2(0) = 160 kJ/mol. These values are compared to (a) isosteric heat of adsorption provided by the Clausius-Clapeyron method and (b) literature data using temperature-programmed desorption, microcalorimetry, and DFT calculations. Forthcoming artides show that the simplicity of the analytical procedures allows studying the impact of the presence of sulfate and VOx/WOy depositions over TiO2, on the nature and heats of adsorption of adsorbed NH3 species.
In this paper, we present an efficient strategic/tactical planning model for offshore oilfield development problem that is fairly generic and can be extended to include other complexities. The ...proposed multiperiod nonconvex MINLP (mixed integer nonlinear programming) model for multifield site includes three components (oil, water, and gas) explicitly in the formulation using higher order polynomials, avoiding bilinear and other nonlinear terms. With the objective of maximizing total NPV for long-term planning horizon, the model involves decisions related to FPSO (floating production, storage, and offloading) installation and expansions, field–FPSO connections, well drilling, and production rates in each time period. The model can be solved effectively with DICOPT for realistic instances and gives good quality solutions. Furthermore, it can be reformulated into an MILP after piecewise linearization and exact linearization techniques that can be solved globally in an efficient way. Solutions of realistic instances involving 10 fields, 3 FPSOs, 84 wells, and 20 years planning horizon are reported, as well as comparisons between the computational performance of the proposed MINLP and MILP formulations.
We report on the boron-doped diamond (BDD) electrodes modified with Prussian Blue (PB) through electrochemical synthesis, open-circuit deposition, and immobilization of Prussian Blue based nanozymes. ...The later allowed attaining the utmost sensitivity of the H2O2 sensor (≈0.14 A M−1 cm−2). Compared to conventional graphite electrodes modified with Prussian Blue, the use of BDD provided twenty times decreased oxygen reduction currents resulting in up to ten times increased signal-to-background ratio of the corresponding modified electrodes. The successful combination of exceptional diamond properties (including wide potential window for BDD electrodes) with advantageous performance characteristics of Prussian Blue sensing layers would open new horizons for H2O2 detection as well as biosensors elaboration.
•Electron transfer rate at the H-terminated B-doped diamond electrodes is sufficient.•Prussian Blue nanozymes immobilization provides the utmost sensitivity towards H2O2.•O2 reduction currents at the doped diamond.|Prussian Blue sensors are 20 times lower
PDF
