Recent progress in CO oxidation over Pt-group-metal catalysts at low temperatures

CO oxidation is probably the most studied reaction in heterogeneous catalysis.This reaction has become a hot topic with the discovery of nanogold catalysts,which are active at low temperatures（at or below room temperature）.Au catalysts are the benchmark for judging the activities of other metals in CO oxidation.Pt-group metals（PGMs） that give comparable performances are of particular interest.In this mini-review,we summarize the advances in various PGM（Pt,Pd,Ir,Rh,Ru）catalysts that have high catalytic activities in low-temperature CO oxidation arising from reducible supports or the presence of OH species.The effects of the size of the metal species and the importance of the interface between the metal and the reducible support are covered and discussed in terms of their promotional role in CO oxidation at low temperatures.

Studying creation of bulk elementary excitation by heaters in superfluid helium-II at low temperatures

In this paper, the obtained experimental results concerning creation of bulk elementary excitations （BEEs） in isotopically pure liquid ^4He at low temperatures -60 mK are discussed. Positive rotons＇ （R^＋-rotons） creation by a pulsed heater was studied. Signals were recorded for the following quantum processes： quantum evaporation of ^4He-atoms from the free liquid-helium surface by the BEEs of the liquid helium-Ⅱ, and BEEs reflection from the free surface back into the bulk liquid. Typical signals are shown, and ratios of signal amplitudes are evaluated. For long heater pulses from 5 to 10 μs, appearance of the second atomic cloud consisting of evaporated ^4He-atoms was observed in addition to the first atomic cloud. It is thought that the first atomic cloud of the evaporated helium atoms consists of very fast ^4He-atoms with energies ～35 K evaporated by positive rotons with the special energies ～17 K （～2ER～2×8.6 K with ER representing the roton minimum energy） corresponding to the third non-dispersive Zakharenko wave. The second cloud of slower ^4He-atoms was created by surface elementary excitations （SEEs or ripplons） possessing the special energies ～7.15 K representing the binding energy. It was assumed that such SEEs can be created by phonons incoming to the liquid surface with special energies ～6.2 K corresponding to the first non-dispersive Zakharenko wave which can interact at the liquid surface with the same phonons already reflected from the surface for long heater pulses. Also, some pulsed-heater characteristics were studied in order to better understand the features of such heaters in low temperature experiments.

Quantum transport characteristics in single and multiple N-channel junctionless nanowire transistors at low temperatures

Single and multiple n-channel junctionless nanowire transistors （JNTs） are fabricated and experimentally investigated at variable temperatures. Clear current oscillations caused by the quantum-confinement effect are observed in the curve of drain current versus gate voltage acquired at low temperatures （10 K-100 K） and variable drain bias voltages （10 mV- 90 mV）. Transfer characteristics exhibit current oscillation peaks below flat-band voltage （VFB） at temperatures up to 75 K, which is possibly due to Coulomb-blocking from quantum dots, which are randomly formed by ionized dopants in the just opened n-type one-dimensional （1D） channel of silicon nanowires. However, at higher voltages than VFB, regular current steps are observed in single-channel JNTs, which corresponds to the fully populated subbands in the 1D channel. The subband energy spacing extracted from transconductance peaks accords well with theoretical predication. However, in multiple-channel JNT, only tiny oscillation peaks of the drain current are observed due to the combination of the drain current from multiple channels with quantum-confinement effects.

Effects of low temperatures on strength and power input into rock failure

Study results of low temperature effects on the strength index and specific power input into rock failure are presented.It has been experimentally determined that within the range of-5 °С to-15 °С,there is a local minimum at which the compression strength and specific power input into failure of some rocks are 10%-50% lower than those at positive temperatures.

Preparation and Properties of Sintered Corundum at Low Temperatures with Nano-η-Al2O3 Powder

In order to reduce the sintering temperature and improve the properties of sintered corundum,corundum specimens were prepared by granulation and sintering with nano-η-A l203 as the raw material and polyvinyl alcohol as the binder.The effects of different sintering temperatures(1550,1600,1650 and 1700℃)and holding time(2,4 and 6 h)on the properties and microstructures of the specimens were studied,and the transformation mechanism ofη-Al203 was analyzed.The results show that dense sintered corundum with bulk density of 3.74 g/cm^3 and apparent porosity of 1.77%is obtained by calcinating at 1650℃for 6 h;the phase transition fromη-Al203 toα-Al203 occurs first on the surface of alumina particles and then diffuses rapidly to the interior;at lower sintering temperatures there is no abnormal growth of crystals,the bonding between the grains is tight,transgranular fracture is the main fracture mode,there are fewer intergranular pores,and the grain size is in the range of 3.5-7.5μm.

Synthesis of Pd nanoparticles supported on CeO_2 nanotubes for CO oxidation at low temperatures

Developing efficient supported Pd catalysts and understanding their catalytic mechanism in CO oxidation are challenging research topics in recent years.This paper describes the synthesis of Pd nanoparticles supported on CeO2 nanotubes via an alcohol reduction method.The effect of the support morphology on the catalytic reaction was explored.Subsequently,the performance of the prepared catalysts was investigated toward CO oxidation reaction and characterized by Nitrogen sorption,X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,and CO-temperature-programmed desorption techniques.The results indicated that the catalyst of Pd on CeO2 nanotubes exhibits excellent activity in CO oxidation at low temperatures,due to its large surface area,the high dispersion of Pd species,the mesoporous and tubular structure of the CeO2-nanotube support,the abundant Ce3＋,formation of Pd–O–Ce bonding,and enhanced metal–support interaction on the catalyst surface.

Planck’s Oscillators at Low Temperatures and Haken’s Perturbation Approach to the Quantum Oscillators Reconsidered

In the first step the extremal values of the vibrational specific heat and entropy represented by the Planck oscillators at the low temperatures could be calculated. The positions of the extrema are defined by the dimensionless ratios between the quanta of the vibrational energy and products of the actual temperature multiplied by the Boltzmann constant. It became evident that position of a local maximum obtained for the Planck’s average energy of a vibration mode and position of a local maximum of entropy are the same. In the next step the Haken’s time-dependent perturbation approach to the pair of quantum non-degenerate Schr?dinger eigenstates of energy is re-examined. An averaging process done on the time variable leads to a very simple formula for the coefficients entering the perturbation terms.

Effective recovery of chalcopyrite at low temperatures using modified ester collector

The effect of a modified ester collector named as BL on the flotation of chalcopyrite at low temperatures was investigated by micro-flotation tests,contact angle measurements,adsorption experiments,laser particle size analysis,cryogenic transmission electron microscopy(Cryo-TEM)and Fourier transform infrared(FTIR)analyses.Micro-flotation tests proved that the collecting ability of BL for chalcopyrite was significantly better than that of N,N-diethyl dithiocarbamate propiononitrile ester(ester-105)at low temperatures.Combined with laser particle size,Cryo-TEM and FTIR analyses,it was found that the particle size of BL in water was smaller than that of ester-105,and the distributed density of BL was higher than that of ester-105 at low temperatures,indicating that BL dispersed well at low temperatures.Therefore,BL was more easily adsorbed on the chalcopyrite surface and improved the surface hydrophobic degree of chalcopyrite,which were also confirmed by the contact angle measurements and adsorption experiments.

Calculation of Apparent Activation Energy of Coal Oxidation at Low Temperatures by Measuring CO Yield

By analyzing previous studies on activation energy of coal oxidation at low temperatures, a theoretical calculation model of apparent activation energy is established. Yield of CO is measured by using the characteristic detector of coal oxidation at 30-90 ℃. The impact of parameters, such as airflow and particle size, on activation energies is analyzed. Finally, agreement was obtained between activation energies and the dynamic oxygen absorbed in order to test the accuracy of the model. The results show that： 1） a positive exponential relation between concentration of CO and temperature in the process of the experiment is obtained： increases are almost identical and the initial CO is low; 2） the apparent activation energies increase gradually with the sizes of particle at the same airflow, but the gradients increase at a decreasing rate; 3） the apparent activation energies increase linearly with airflow. For the five coal particles, the differences among the energies are relatively high when the airflow was low, but the differences were low when the airflow was high; 4） the optimum sizes of particle, 0.125-0.25 ram, and the optimum volume of airflow, 100 mL/min, are determined from the model; 5） the apparent activation energies decrease with an increase in oxygen absorbed. A negative exponential relation between the two is obtained,

Oxidation of CO on Nanometer Metal Oxides at Low Temperatures

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A Review on Complete Oxidation of Methane at Low Temperatures

This paper reviews recent developments in complete oxidation of methane atlow temperatures over noble metal catalysts in the past 20 years. The Pd/Al_2O_3 catalyst system isfully discussed. The review mainly focuses on the kinetic aspects of methane oxidation over thiscatalyst, and methane activation behavior over Pd and PdO phases (the form of PdO on the surface,transient behavior, the nature of the active sites, the influence of metal particle size and theirstructure sensitivities, and so on). Some Pd catalysts supported on other oxides besides the Al_2O_3support are briefly discussed. Possible routes of non-noble metal catalysts as substitutes for thePd catalyst are also proposed.

Isolation and Characterization of Microorganisms for Degradation of Minimal Oils and Fats at Low Temperatures

The isolation of microorganisms for biodegradation of minimal fats and oils at low temperatures was reported. By using rapeseed oil as a sole carbon source, six strains were isolated from five kinds of oils/fats-contaminated wastewater, soil, and active sludge. Among them, two strains which show the highest oil removal ratios were identified as Pseudomonas pseudoalcaligenes and Pseudomonas mendocina, respectively. The experiments of orthogonal impact conditions show that the optimal oil degradation condition is at pH 8.0, 5 ℃ and 100 mg/L oil. Under this condition, the rapeseed oil degradation ratios of two strains after 24 hours amount to 92.6% and 92.0% respectively, whereas the removal ratios of lard decrease to 39.5% and 54.3%.

Highly efficient H-bonding charge-transfer complex for microsupercapacitors under extreme conditions of low temperatures

Owing to sluggish ionic mobility at low temperatures, supercapacitors, as well as other energy-storage devices, always suffer from severe capacity decay and even failure under extreme low-temperature circumstances. Solar-thermal-enabled self-heating promises an attractive approach to overcome this issue.Here, we report a unique H-bonding charge-transfer complex with a high photothermal conversion efficiency of 79.5% at 405 nm based on chloranilic acid and albendazole. Integrated with a microsupercapacitor, the chloranilic acid-albendazole complex(CAC) film prompts an apparent temperature increase of 22.7 °C under 1 sun illumination at-32.6 °C, effectively elevating the working temperature of devices.As a result, the rate capability of the microsupercapacitor has been significantly improved with a 17-fold increase in capacitance at a current density of 60 μA cm^(-2), leading to outstanding low-temperature performances. Importantly, the integrated device is capable of working at a low temperature of-30 °C in the open air, which demonstrates the potential of CAC in practical applications for low-temperature ultracapacitive energy-storage devices.

A More Precise Determination of Gear Oil Viscosity at Low Temperatures

Low temperature fluidity of gear oils is an important fluid property as it directly impacts the useful life of a gear set.This paper compares low temperature fluidity measurement precision of ASTM D6821 and ASTM D2983.Both tests are identical in the way they thermally condition the sample prior to viscosity measurement.While ASTM D2983 is cited in many current specifications,ASTM D6821 offers users and formulators a more accurate estimate of gear oil low temperature fluidity.The primary benefit in using ASTM D6821 is better precision.ASTM D6821 accomplishes this by automating the steps from prior to preheat through to viscosity measurement at end of test.

Alkyl dimethyl betaine activates the low-temperature collection capacity of sodium oleate for scheelite

The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement.The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12℃. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures.

Electrolyte Design for Low‑Temperature Li‑Metal Batteries:Challenges and Prospects

Electrolyte design holds the greatest opportunity for the development of batteries that are capable of sub-zero temperature operation.To get the most energy storage out of the battery at low temperatures,improvements in electrolyte chemistry need to be coupled with optimized electrode materials and tailored electrolyte/electrode interphases.Herein,this review critically outlines electrolytes’limiting factors,including reduced ionic conductivity,large de-solvation energy,sluggish charge transfer,and slow Li-ion transportation across the electrolyte/electrode interphases,which affect the low-temperature performance of Li-metal batteries.Detailed theoretical derivations that explain the explicit influence of temperature on battery performance are presented to deepen understanding.Emerging improvement strategies from the aspects of electrolyte design and electrolyte/electrode interphase engineering are summarized and rigorously compared.Perspectives on future research are proposed to guide the ongoing exploration for better low-temperature Li-metal batteries.

Revealing the key role of non-solvating diluents for fast-charging and low temperature Li-ion batteries

Fast-charging and low temperature operation are of vital importance for the further development of lithium-ion batteries(LIBs),which is hindered by the utilization of conventional carbonate-based electrolytes due to their slow kinetics,narrow operating temperature and voltage range.Herein,an acetonitrile(AN)-based localized high-concentration electrolyte(LHCE)is proposed to retain liquid state and high ionic conductivity at ultra-low temperatures while possessing high oxidation stability.We originally reveal the excellent thermal shielding effect of non-solvating diluent to prevent the aggregation of Li^(+) solvates as temperature drops,maintaining the merits of fast Li transport and facile desolvation as at room temperature,which bestows the graphite electrode with remarkable low temperature performance(264 mA h g^(-1) at-20 C).Remarkably,an extremely high capacity retention of 97%is achieved for high-voltage high-energy graphite||NCM batteries after 250 cycles at-20 C,and a high capacity of 110 mA h g^(-1)(71%of its room-temperature capacity)is retained at-30°C.The study unveils the key role of the non-solvating diluents and provides instructive guidance in designing electrolytes towards fast-charging and low temperature LIBs.

Accelerated Sequential Deposition Reaction via Crystal Orientation Engineering for Low-Temperature,High-Efficiency Carbon-Electrode CsPbBr_(3) Solar Cells

Low-temperature,ambient processing of high-quality CsPbBr_(3)films is demanded for scalable production of efficient,low-cost carbon-electrode perovskite solar cells(PSCs).Herein,we demonstrate a crystal orientation engineering strategy of PbBr_(2)precursor film to accelerate its reaction with CsBr precursor during two-step sequential deposition of CsPbBr_(3)films.Such a novel strategy is proceeded by adding CsBr species into PbBr_(2)precursor,which can tailor the preferred crystal orientation of PbBr_(2)film from[020]into[031],with CsBr additive staying in the film as CsPb_(2)Br_(5)phase.Theoretical calculations show that the reaction energy barrier of(031)planes of PbBr_(2)with CsBr is lower about 2.28 eV than that of(O2O)planes.Therefore,CsPbBr_(3)films with full coverage,high purity,high crystallinity,micro-sized grains can be obtained at a low temperature of 150℃.Carbon-electrode PSCs with these desired CsPbBr_(3)films yield the record-high efficiency of 10.27%coupled with excellent operation stability.Meanwhile,the 1 cm^(2)area one with the superior efficiency of 8.00%as well as the flexible one with the champion efficiency of 8.27%and excellent mechanical bending characteristics are also achieved.

Low-molecular-weight supramolecular adhesive with resistance to low temperatures

The design of adhesive materials with strong adhesion capacity at low temperatures is a great challenge.Herein,we report a low-molecular-weight supramolecular adhesive that exhibits good adhesion performance to various surfaces at low temperatures(from-18℃ to-80℃).Moreover,this supramolecular adhesive has good adhesion ability in the presence of water.

Boosting the energy density of sulfide-based all-solid-state batteries at low temperatures by charging to high voltages up to 6 V

Sulfide electrolyte-based all-solid-state batteries(ASSBs)are potential next generation energy storage technology due to the high ionic conductivity of sulfide electrolytes and potentially improved energy density and safety.However,the performance of ASSBs at/below subzero temperatures has not been explored systematically.Herein,low temperature(LT)performance of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)|Li_(9.54)Si_(1.74)P_(1.44)S11.7Cl_(0.3)(LiSPSCl)|Li_(4)Ti_(5)O_(12)(LTO)ASSBs was investigated.By charging the ASSB to 6 V at−40℃,a capacity of 100.7 mAh∙g^(−1)at 20 mA∙g^(−1)was achieved,which is much higher than that charged to 4.3 V(4.6 mAh∙g^(−1))at−40℃.Moreover,atomic resolution microscopy revealed that the NCM811 remained almost intact even after being charged to 6 V.In contrast,NCM811 was entirely destructed when charged to 6 V at room temperature.The sharp difference arises from the large internal charge transfer resistance at LT which requires high voltage to overcome.Nevertheless,such high voltage is not harmful to the active material but beneficial to extracting most energy out of the ASSBs at LT.We also demonstrated that thinner electrolyte is favorable for LT operation of ASSBs due to the reduced ion transfer distance.This work provides new strategies to boost the capacity and energy density of sulfide-based ASSBs at LT for dedicated LT applications.