Simple Activation Process Research Articles

Spartina alterniflora-Derived Carbons for High-Performance Oxygen Reduction Reaction (ORR) Catalysts

Being an alien species, Spartina alterniflora has occupied the living space of native animals and plants, causing irreversible damage to the environment. Converting Spartina alterniflora into carbon or its derivatives offers a valuable solution to manage both invasive biomass and an energy shortage. Herein, through a simple activation process, we successfully prepared Spartina alterniflora-derived carbon (SAC) and its N-doped derivative SANC, and used them as metal-free catalysts for an oxygen reduction reaction (ORR). SAC exhibits good electrochemical performance and holds significant potential in catalysis. After N-doping by melamine as a nitrogen source, electronegativity is redistributed in SANC, leading to enhanced performance (a half-wave potential of 0.716 V vs. RHE, and a four-electron transfer pathway with a H2O2 yield of only 2.05%). This work presents a straightforward and cost-effective approach to the usage of obsolete invasive biomass and shows great potential in energy generation.

Full solar-spectrum available Z-scheme MOF-on-MOF heterostructure for highly efficient photocatalytic VSCs removal

The construction of efficient photocatalysts with strong response to sunlight is crucial for clean and sustainable pollutant degradation and environmental remediation. Herein, a novel MOF-on-MOF structural photocatalyst named HKU@MIL with Z-scheme heterojunction was successfully designed. The light response of the composites effectively extends to the whole solar spectrum through a simple activation process, addressing the issue of the low utilization of sunlight by photocatalysts. The photocatalytic degradation rate of methyl mercaptan by activated HKU@MIL is 2.2, 3.2, and 1.8 times higher than that of NH2-MIL-125, HKUST-1, and HKU/MIL-5 (physical mixtures), respectively. Under simulated sunlight irradiation, the rate constant increases to 0.507 min−1, which is 1.4 times higher than that under visible light. Additionally, the composites exhibit good photocatalytic performance when irradiated with near-infrared light alone. The heterojunction type of the photocatalyst was investigated according to in-depth analysis of X-ray photoelectron spectroscopy. Additionally, the interfacial charge transmission mode of the composites and the probable pathways for methyl mercaptan degradation were explored through band structure analysis, radical quenching tests and electron spin resonance analysis. The improved photocatalytic performance of activated HKU@MIL can be attributed to the full solar spectral response and the successful creation of the Z-scheme electron migration channel, which serves to reinforces the electron pump effect. It achieves this by improving the transmission of photogenerated carriers and ensuring the strongest redox potential. This work presents a new perspective on enhancing the utilization of sunlight by photocatalysts and improving the photocatalytic performance of heterojunction photocatalysts used in environmental remediation.

Morphology reconstruction of nickel cobalt layered double hydroxides induced by electrolyte concentrations triggers high performance of supercapattery storage

AbstractNickel cobalt layered double hydroxides (NiCo LDHs) have emerged as ideal electrode materials for supercapattery due to their high specific surface area and excellent cycling stability. Morphology control plays a unique role in regulating the performance of the NiCo LDHs. Herein, the morphology of NiCo‐LDHs electrode is optimized for enhancing energy storage by a simple activation process with different concentrations of the electrolyte. During the activation process, electrochemical morphology reconstruction occurs on the electrode surface. With a 2 m KOH electrolyte, the NiCo‐LDH electrode transforms from nanosheets to nanoflower, which aids in reducing the distance of ion transport. The reconstructed NiCo‐LDH exhibits an ultra‐high specific capacity of 2809 C g−1 at a current density of 1 A g−1, outperforming most of NiCo LDHs. At a high current density of 10 A g−1, the capacity retention rate remains above 72.7% after 3000 cycles. An asymmetric supercapacitor is fabricated with activated carbon material as the negative electrode, the energy density is 36 Wh kg−1 at the power density of 732 W kg−1. The strategy proposed in the study, which involves concentration‐controlled morphology optimization for energy storage enhancement, holds great practical significance for the field of supercapatteries.

Recycling Used-Coffee Grounds into Hierarchical Nanostructured Carbon for Supercapacitor Application

Hierarchical nanostructured activated carbon electrode material was prepared from the used-coffee grounds to fabricate a cost-effective, scalable and high-performance symmetric supercapacitor. The interconnected, disordered and microporous material was synthesized in a simple two-stage method of chemical activation with zinc chloride followed by direct pyrolysis of the coffee grounds at 900 ºC in nitrogen atmosphere. The N2 adsorption and desorption analysis showed that the prepared material had an extraordinary surface area of ~1178 m2 g-1. The fabricated symmetric supercapacitor device in non-aqueous tetraethylammonium tetrafluoroborate (TEABF4) electrolyte exhibited 2.7 V cell voltage with superior specific capacitance, energy and power density of 129 F g–1, 56.4 Wh kg–1 and 797.9 W kg–1, respectively. Besides, it also had a high specific capacitance retention of 99% even after 10,000 cycles. This work demonstrated an effective approach to transform coffee grounds into high performance electrode material for renewable energy devices. The observed electrochemical performance evidently showed that the materials derived from waste coffee grounds could be recycled into potential electrode material for supercapacitors. The cost-effectiveness and abundance of waste coffee grounds combined with the simple activation process and high performance of the synthesized material increased its feasibility for commercial applications in energy storage devices.

Supercooled sodium acetate aqueous solution for long-term heat storage to support heating decarbonisation

Heating decarbonisation through electrification requires the development of novel heat batteries. They should be suitable for the specific application and match the operation conditions of domestic renewable energy sources. Supercooled liquids, often considered a drawback of phase change materials, are among the most promising technologies supporting heating decarbonisation. Although some studies have shed light on stable supercooling, the fundamentals and stability remain open problems not always accompanied by relevant experimental investigations. This research critically analyses the physic and chemistry of sodium acetate (SA, NaCH3COO) aqueous solution, a low-cost, non-toxic, and abundant compound with stable supercooling for long-term heat storage. It has an appropriate phase change temperature for high-density heat storage using heat pumps or solar thermal technologies in residential applications. The existing discrepancies in literature are critically discussed through a systematic experimental evaluation, providing novel insights into efficient material design and appropriate boundary conditions for reliable material use in long-term heat batteries. Despite previous studies showing that the thermal reliability and stability of sodium acetate aqueous solution as a supercooled liquid for heat storage cannot be guaranteed, this study demonstrates that through an appropriate encapsulation and sealing method, the peritectic composition of sodium acetate solution (p-SA 58 wt%) can be used as a supercooled liquid for long-term heat storage with a stable melting temperature of 57 °C, appropriate for domestic heat technologies. It is demonstrated that energy storage efficiency can be maintained under cycling, with a constant latent heat storage capacity of 245 kJ/kg and a volumetric storage density of 314 MJ/m3. It was confirmed that the material should achieve a fully-melted state for stable supercooling. Finally, local cooling and retaining seed crystals through high pressure were highlighted as the most suitable basic principles for successful crystallization and heat release. This promising material can store energy for long periods without latent heat losses due to its stable subcooling. Latent heat can be released when required at any selected time and temperature just by a simple activation process.

Removal of toxic cadmium using a binary site ion‐exchange material derived from waste printed circuit boards

AbstractBACKGROUNDAdsorption has been widely applied in wastewater treatment for heavy metal removal. Due to the high cost of adsorbent materials, various types of materials including agricultural, industrial wastes and naturally abundant materials have emerged as low‐cost adsorbents in recent years. However, enhancement processes need to be developed to improve the adsorption capability of the raw materials. It is still a challenge to find an economic material with high adsorption capacity. This paper demonstrates a strategy to activate a recycled waste material using a simple activating process, while significantly improving the adsorption capacity of cadmium from wastewater.RESULTSThe raw material feedstock is the non‐metallic aluminosilicate material obtained from the recycling of waste printed circuit boards (PCBs). By a simple thermal alkali activation process using potassium hydroxide as activation agent, the product material shows a strong capability of cadmium removal from effluent containing a high adsorption capacity of 2.12 mmol g−1. Initial metal concentration, dosage and pH effect on the adsorption isotherm and kinetics have been investigated. The experimental results include full characterization tests on this waste PCB‐derived adsorbent, and the in situ measurement of cadmium, calcium and potassium ions, since all are involved in the exchange sorption mechanism.CONCLUSIONBy combining kinetic modelling analysis and X‐ray photoelectron spectroscopy, the novel adsorption mechanism has been explained and quantified as a dual ion‐exchange mechanism with the millimoles of cadmium exchanged mass balancing with the millimoles of calcium and 0.5 mmol potassium going into solution. © 2021 Society of Chemical Industry (SCI).

Activated carbon prepared from catechol distillation residue for efficient adsorption of aromatic organic compounds from aqueous solution

At present, activated carbon (AC) derived from industrial wastes has a great practical significance. In this work, residue activated carbon (RAC) was successfully synthesized from catechol distillation residue by a simple activation process based on two steps. The optimized RAC (RAC-800, activated at 800 °C) had high specific surface area (1800 m2/g) and large total pore volume (0.91 cm3/g). RAC-800 portrayed the evident increase of the graphitic structure and possessed abundant functional groups. Catechol (CC), phthalic acid (PA) and dimethyl phthalate (DMP) were chosen as typical pollutant to investigate the effect of different functional groups on adsorption aromatic compounds, and the equilibrium adsorption capacity of RAC-800 for CC, PA and DMP was 221.5, 365.0 and 449.9 mg/g, respectively. The adsorption behaviors were systematically studied by the combination of kinetic and thermodynamic model. The adsorption process was dominated by the π-π interaction, assisted by hydrogen bonding, hydrophobic and electrostatic interactions. In addition, regeneration study showed that the adsorption capacity can still remain over 88.5% after five cycles. In total, fine chemical distillation residues are promising to turn into the precursor of activated carbon, which has potential to be used as a good adsorbent for removal of aromatic compounds.

Metal catalysts supported on biochars: Part I synthesis and characterization

In the current study, synthesis and detailed characterization of cellulose biochars as a waste biomass model component and vine shoot biochars as a real waste biomass catalyst was performed. Although initially biochars exhibit poor textural properties, a simple activation process can make them much more suitable as a catalyst supports. A combination of physical (CO2) and chemical activation (ZnCl2) was evaluated. The characterization results indicated that the surface area and pore volume of the biochars have increased significantly by chemical activation treatment with ZnCl2. A series of metal catalysts (Pd, Au and Ru) supported on biochars was prepared and characterized. The prepared materials represent a set of noble metal catalysts supported on biochars with different textural and surface properties, which can be used to evaluate the catalytic role of the active phase and carbon support nature in catalytic reactions of interest, such as hydrodeoxygenation, described in the part II.

Microporous waste charcoals for redox-mediated supercapacitors

The energy density of supercapacitors could be improved significantly using microporous carbon-based materials (MP-CMs) with multitudinous redox-active heteroatoms through the hybrid charge storage behaviors of both pseudocapacitance and electrochemical double layer capacitance in a redox-mediated aqueous electrolyte system. Waste-derived MP-CMs were prepared using a simple activation process and used as high-performance electrode materials for redox-mediated supercapacitors, showing a high specific capacitance of ˜512Fg−1 and a reasonable rate and cycling performance.

Cicada slough-derived heteroatom incorporated porous carbon for supercapacitor: Ultra-high gravimetric capacitance

Heteroatom incorporated porous carbon from cicada slough, has been synthesized through a simple activation process. The cicada slough-based porous carbon has high potency of naturally-derived heteroatom functionalities (∼12.06% atomic ratio of nitrogen, oxygen, sulfur, and phosphorus), well-developed microporosity and high specific surface area (1676 m2 g−1). Supercapacitor involves the as-obtained carbon as electrode material showing ultra-high specific capacitance of 355 F g−1 at the current density of 1 A g−1 and excellent rate capability of 284 F g−1 at 30 A g−1. The retention of specific capacitance of the working electrode remains over 90% after 3000 cycles at 10 A g−1. Single electrode in the symmetric-two-electrode test also delivers high specific capacitance of 274 F g−1 with the energy density up to ∼9.0 W h kg−1 in aqueous electrolyte. These outstanding results suggest the biomass derived porous carbon possessing the potential for the fabrication of high performance supercapacitors.

Ag/Biochar composite for supercapacitor electrodes

A new composite material was obtained using a simple activation process of biochar (BC) and high performance supercapacitor (SC) electrodes were fabricated. BC was attained by carbonization of infested ash tree residue at 700 °C and was then chemically activated in an Ag2SO4/HNO3 solution. The physical properties of the activated – Ag/BC composite product and the electrochemical properties of electrodes fabricated with this composite material were investigated and compared with properties of electrodes fabricated with activated biochar (a-BC). The a-BC was obtained by activation of BC in HNO3. Experimental results with the Ag/BC composite based electrodes show favourable electrochemical performance. A high specific capacitance of 494 F g−1 was achieved in an aqueous LiN((SO2CF3)2) electrolyte, which is almost 31.4% higher than that of the a-BC based electrodes (376 F g−1) and 42% higher than was previously reported (335 F g−1 [Kouchachvili et al. (2015)]) using the identical aqueous electrolyte. Also, high cycling stability with a specific capacitance retention of 98.6% was demonstrated after 2000 cycles. Symmetric SC cells were therefore assembled with the Ag/BC composite and the a-BC based electrodes. The former cell has since shown an excellent energy density of 12.8 Wh kg−1 that is 37% higher than the energy density of the later SC cell (8 Wh kg−1), whereas the power density of both SC cells remained the same (366 W kg−1 at a charge/discharge current of 1.3 mA).

Three-dimensional cheese-like carbon nanoarchitecture with tremendous surface area and pore construction derived from corn as superior electrode materials for supercapacitors

Highly porous carbon nanoarchitectures (HPCNs) were derived from biomass materials, namely, corn fibers (CF), corn leafs (CL), and corn cobs (CC). We surprisingly found that by a very simple activation process the CF, CL, and CC materials can be transformed into exciting two-dimensional (2D) and three-dimensional (3D) carbon nanoarchitectures with excellent physicochemical properties. FESEM and HRTEM results confirmed a three different carbon forms (such as foams-like carbon, carbon sheets with several holes and cheese-like carbon morphology) of HPCNs. Huge surface area (2394–3475m2/g) with excellent pore properties of HPCNs was determined by BET analysis. Well condensed graphitic plans of HPCNs were confirmed by XRD, XPS and Raman analyses. As an electrode material, HPCNs demonstrated a maximum specific capacitance (Cs) of 575F/g in 1.0M H2SO4 with good stability over 20,000 cycles. The CC-700°C showed a tremendous Cs of 375F/g even at 20000th cycles. To the best of our knowledge, this is the highest Cs by the biomass derived activated carbons in aqueous electrolytes. The CC-700°C exhibited excellent charge-discharge behavior at various current densities (0.5–10Ag−1). Notably, CC-700°C demonstrated an excellent Cs of 207F/g at current density of 10Ag−1. An extraordinary change–discharge behavior was noticed at low current density of 0.5Ag−1.

Rice husk and rice husk ash reutilization into nanoporous materials for adsorptive biomedical applications: A review

Abstract The continuous generation of rice husk biomass makes this waste biomass a consistent and renewable resource for carbon zero power generation. Biochar from the power generation industry could be further utilized and converted into activated carbon through a simple activation process, foregoing the conventional carbonization process. Complete combustion of rice husk into rice husk ash could be subsequently processed into sodium silicate with little difficultly since more than 90%of the rice husk ash constituent is silica. Sodium silicate is used mainly as a precursor for both the synthesis of mesoporous silica and zeolite. This paper reviews on the various nanoporous adsorbents derived from a single rice husk biomass.

Temperature- and frequency-dependent optical properties of ultrathin Au films

While the optical properties of thin metal films are well understood in the visible and near-infrared range, little has been done in the midinfrared and far-infrared region. Here we investigate ultrathin gold films prepared on $\text{Si}(111)(7\ifmmode\times\else\texttimes\fi{}7)$ in UHV by measuring in the frequency range between 500 and $7000\text{ }{\text{cm}}^{\ensuremath{-}1}$ and for temperatures between 300 and 5 K. The nominal thickness of the gold layers ranges between one monolayer and 9 nm. The frequency and temperature dependences of the thicker films can be well described by the Drude model of a metal when taking into account classical size effects due to surface scattering. The films below the percolation threshold exhibit a nonmetallic behavior; the reflection increases with frequency and decreases with temperature. The frequency dependence can partly be described by a generalized Drude model. The temperature dependence does not follow a simple activation process. For monolayers we observe a transition between surface states around $1100\text{ }{\text{cm}}^{\ensuremath{-}1}$.

Preparation and hydrogen storage properties ofMg2Ni intermetallic nanoparticles

In this work we investigated the hydrogen storage properties of stoichiometricMg2Ni intermetallic nanoparticles produced from Mg and Ni nanoparticles. The mean size of theMg2Ni particles is about 30–50 nm and the lattice constants of theMg2Ni compoundare a = 5.22 Å, c = 13.29 Å.The Mg2Ni compound showed excellent hydrogen storage properties withoutactivation. It can absorb 2.77, 2.93 and 3.03 wt% hydrogen at 523, 573and 623 K respectively. After one simple activation process, the obtainedMg2Ni absorbed 1.74, 2.07, 2.31 and 2.82 wt% hydrogen at 293, 348, 426 and 493 K respectively. Theabsorption and desorption plateau hydrogen pressures are about 2.5 and 0.8 bar at 523 K,5.9 and 3.4 bar at 573 K and 12.7 and 9.7 bar at 623 K. The resulting van’t Hoff equation islog(P/bar) = −3464/T+6.541 and the formationenthalpy (ΔH)and entropy (ΔS) for the Mg2NiH4 are −66.32 kJ/mol H2 and −125.3 J K−1/mol H2.

Successful implantation of in vitro-matured, electro-activated oocytes in the pig

In the present study, we derived parthenogenetic porcine fetuses from in vitro-matured oocytes following a simple activation process in order to evaluate their developmental limitations in-vivo. Follicular oocytes collected from gilts at local slaughterhouses were matured for 48 h. They were subjected to a single square pulse of direct current for 100 μsec at 1,500 V/cm and then treated with 5 μg/mL cytochalasin B for 4 h to obtain activated diploid oocytes. The diploids were cultured in modified Whitten's medium until transfer. Diploids which had cleaved to the 2 and 3 to 4-cell stages were transferred to oviducts of recipients. Live and/or dead parthenogenetic fetuses were recovered in 6 of 8 trials at 17, 18, 19, 24 and 29 d post activation. The total proportion of fetuses to transferred diploids was 31.3% (62/198). When fetuses were recovered at 19 d post activation, the proportion of development into fetuses was 71% (15/21). Our results, however, suggest that periods of gestation longer than 19 d resulted in a decrease of these proportions to 45% (18/40) at 24 d and to 18% (7/40) at 29 d. The hearts were beating in nearly all of the fetuses recovered at 19, 24 and 29 d post activation. Thus, parthenogenetic porcine diploids developed to at least the stage of limb-bud formation beyond the early heart-beating stage. Abnormalities were also externally visible on some fetuses. Formation of cyst-like structures in the heart and liver, and insufficient development of the head region and acephali were observed in some cases.

ABOUT THE CROSSOVER PHENOMENON FOR VRH-CONDUCTIVITY

In a number of recent publications observations of the phenomenon of crossover from the Efros-Shklovskii (ES)-law to the Mott-law in VRH-conductivity were reported. In some experiments, deviations were observed from a straight line in a lnR vs T−1/2 plot to lower resistance values with increasing temperature. However, deviations to higher resistance with increasing temperature should be observed. In other experiments deviations from the “T−1/2 law” to higher resistances with decreasing temperature were observed. This effect was considered as a transition to a simple activation process, “T−1 law”, caused by the appearance of a hard gap at the Fermi level. In the present work an alternative explanation is given, based on the idea that the temperature range showing the “T−1/2 behaviour” actually corresponds to the crossover regime, while the real ES-regime is only reached in the low-temperature limit.

Effect of pressure on 14N nuclear quadrupole relaxation in hexamethylenetetramine

14N nuclear quadrupole resonance frequencies and spin-lattice relaxation time, T1, in hexamethylenetetramine (HMT) were measured as a function of hydrostatic pressure up to 6 katm at 257, 273, 294.5, 309, and 317°K. For the three higher isotherms T1 depends exponentially on pressure up to 3 katm. In this region T1 is determined mainly by molecular reorientation of the tetrahedral HMT molecule around its four threefold axes. This mechanism is discussed in terms of a simple activation process. The activation volume, ΔV*=23.6±1 cm3/mole, and activation enthalpy, ΔH*=17±1 kcal/mole were determined. From thermal expansion and compressibility data, the thermal pressure, Pt = T(∂p/∂T)v, of 6.2 katm and activation energy ΔE* = 12–15 kcal/mole were deduced. These values of ΔH*, ΔE*, and ΔV* are higher than the corresponding values reported by Anderson and Slichter for three other organic solids and might indicate the effect of the large number of hydrogen bonds in HMT.

Processus de l'ecoulement visqueux des hauts polymères

AbstractTwo recent theories concerning the viscosity of high polymers are summarized: the first one, by Bueche, is based on a complex activation process; the other one, established by Cohen and Turnbull to explain the empirical equation of Williams, Landel, and Ferry, is based on the value of the free volume. The discrepancies with the experimental values are emphasized. A mechanism of deformation is proposed which implies that the displacement of a segment of a macromolecule requires the localization of no holes, at least, in a volume which contains No segments Then, the variation of the number of holes with the temperature is computed, with account of the flex energy of the backbone chain and the formation energy of holes (like Flory, and Gibbs and di Marzio). The theoretical results are in good agreement with the experimental values of the variation of the viscosity with the temperature, the second‐order transitions (thermal expansion and heat capacity), and the variation of the glass temperature with the molecular weight. A simple activation process can also produce the deformation and has the most important contribution at low temperature. It is believed that similar mechanism of diffusion of holes can also explain the viscosity of mineral glasses.

Relationship between the Intrinsic or Intrinsicoid deflection and Time of Arrival of Activation by Unipolar Lead Ecg

In clinical diagnosis of ventricular hypertrophy, bundle branch brock, premature heart beat, tricuspidal- and aortic valvular insufficiency, it is of great significance to determine the time of arrival of activation in ECG. However, there still remains a contraversy as to the point indication it. For example, the onset of ingrinsic or intrinsicoid deflection is regarded as the point marking this by Lewis, Wilson in early stage and many other authors, while the end of this deflection is considered to mark it by Wilson. This report was made to elucidate the accurate relationship between it and intrinsicoid deflection. According to our results in calculation, the actual instant of arrival of activation could be reperesented by cross point of tracing with zero-line when the equivalent double layer, perpendicular to the ling axis of straight muscle strip, was moved from one end to another. The time interval between the onset of the int. defl. and the cross point was variablw according to the transmission rate of activation and the distance from electode to muscle strip. When the equivalent double layer, oblique to hte long axis of the muscle strip,w was moved from one end to another, it could not be reperesented by cross point, differing from above mentioned case. Consequently, the onset of intrinsicoid deflection or the cross point of this deflection with zero-line could not be regarded as the representative point of arrival of activation even in simple activation process like above mentioned cases. Since the activation process in human heart is notso simple as that applying to above cases, we want to calculate the potential variation arising in more complicated activation process. When we calculated the potential change at a given point without a hollow polaraized sphoere in a certain process of activation, the time of arrival of activation was somewhre within the duration of intrinsicoid deflection. Moreover, when we calculated the potential variation at many points without heart in a feew process og activation, the arrival of activation occurred some where during the intrinsicoid deflection and was not upon a specific point like the onset or the end of the deflection. These caliculations were made on the schema of heart quoted from the atlas of anatomy by Toldt Hochstetter, assuming the every equivalent double layer in each stadium of activation as a disk. It must be noted that the intrinsicoid deflection is not necessarily sharp and large deflection but sometimes smaller than the deflection due to the extrinsic effect, and it is not always easy to point out the intrinsicoid deflection in ECG. Comparing these results of calculation with those of experiments pwerformed on toad heart, recording the contiguous bipolar lead ECG and unipolar lead ECG simultaneously, we could observe that the both results coincident very well. We may conclude that the onset or the end ofthe intrinsicoid deflection can not be interpreted as the point indicating the arrival of activation as Lewis Wilson and others say, and that ingrinsicoid deflection is not neccessarily a large and sharp deflection but sometimes smaller then the deflection due to extrinsic effect. In general, the time of arrival of activation lies somewhere during the intrinsicoid deflection, bu can not be defined on a specific point.