Conventional Two-step Method Research Articles

Rational design and preparation of the modified polyimide copolymer with superior anti-gamma irradiation

To improve polymer-based bonded solid lubricating materials with excellent anti-gamma irradiation performance, a polyimide (BPI, Polyimide containing hexafluoropropane 2,2-bis(3-amino-4-hydroxyphenyl)diamine monomer) copolymer containing phenolic hydroxyl and trifluoromethyl groups was synthesized based on a conventional two-step method. Comparative studies have been conducted to investigate the effects of gamma irradiation on microstructure, thermal stability, mechanical and tribological properties under the different irradiation dose conditions. The results show that, compared with the pure polyimide (PI) and corresponding coatings, the modified BPI copolymer and coatings have better gamma-ray irradiation resistance duo to the copolymer contains lots of the activated phenolic hydroxyl groups and fluorine, which could be effectively inhibit the active destruction of parts of chain structure of copolymer, resulted in the BPI copolymer and BPI based coatings possess good comprehensive mechanical and tribological properties after 1000 kGy gamma irradiation. This study provides a novel approach for the design and preparation of lubricating coatings for nuclear energy systems.

High thermal resistance biobased copolyester from 2,5-Thiophenedicarboxylic acid with excellent gas barrier properties

Driven by sustainable development strategies, bio-based polyesters have received significant attention due to renewable bio-derived monomers and various unique properties. In this study, a series of high molecular weight bio-based poly(ethylene-co-2,2,4,4-tetramethyl-1,3-cyclobutylene thiophenedicarboxylate) (PETTh) copolyesters on the basis of an emerging bio-derived aromatic diacid, 2,5-thiophenedicarboxylic acid (TDCA), was synthesized by a conventional two-step melt polycondensation method. Copolymers were random copolyesters with weight-average molecular weights (Mw) in the range from 65,400 to 84,100 g/mol. Their comprehensive properties, including thermal transition properties, thermal stability, mechanical properties, gas barrier properties, as well as optical transparency were systematically investigated. Rigid 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) cyclic diol contributed a positive effect to thermal resistance, leading to the glass transition temperature (Tg) growing from 65.3 °C of PETh to 85.3 °C of PET42Th. Furthermore, the mechanical properties, gas barrier properties and optical transparency were improved as diol segment was incorporated. Especially, all copolyesters displayed great ductility with elongation at break between 54 and 195 %. Meanwhile, the gas barrier properties of copolyesters were 3.9-fold to 16.3-fold for CO2 and 3.0-fold to 6.0-fold for O2 better than PET. Therefore, PETTh copolyesters might potentially substitute for commercial PET and they are extremely suitable for food packaging materials.

Developing a Novel Hybrid Nanofluid Preparation Method Using the Droplet Generation Method: Predicting the Thermal Conductivity, Viscosity, and Magnetic Properties Compared to the Conventional Two-Step Method

Developing a Novel Hybrid Nanofluid Preparation Method Using the Droplet Generation Method: Predicting the Thermal Conductivity, Viscosity, and Magnetic Properties Compared to the Conventional Two-Step Method

In situ X-ray CT visualization of hydrogen bubbles inside the porous transport layer of a direct toluene electro-hydrogenation electrolyzer

The organic hydride toluene/methylcyclohexane is an attractive hydrogen carrier. The direct electro-hydrogenation of toluene to methylcyclohexane has a higher energy efficiency compared to the conventional two-step method. Yet, there are factors inhibiting the toluene supply to the cathode reaction site and reducing the conversion rate to methylcyclohexane. Thus, hydrogen may be generated as a side reaction. Understanding how hydrogen bubbles are distributed is crucial regarding the design optimization of these electrochemical devices. This work presents, for the first time in a direct toluene electro-hydrogenation electrolyzer, the X-ray visualization of hydrogen bubbles inside the porous electrode. The concentration of bubbles was higher near the cathode catalyst and tended to increase with the electric current and operating time. Bubble distribution spreads across the active area when using flat field plates. As for rib-and-channel field plates, despite bubbles mostly concentrated beneath ribs, the total hydrogen accumulated inside the porous electrode could be reduced.

Engineering Stable and Affordable Meta-Aluminate Intercalated Mafic Hydrotalcite for Superior Bromate Remediation

In this study, one type of layered double hydroxide (LDH), the meta-aluminate intercalated mafic-modified hydrotalcite (LDH-2), was engineered through an unprecedentedly facile, affordable one-step procedure. In the interest of meticulous perception regarding our superior strategy, the conventional two-step synthesis method—the fabrication of optimal mafic-modified hydrotalcite through the coprecipitation and roasting process followed by a second aging step (LDH-1)—was also synthesized. After scrutinization of as-derived nanostructures, the adsorption capacity of both structures for bromate remediation was elaborated. When the effect of experimental variation was optimized and the impact of various ions was investigated, the more astounding performance of LDH-2 (0.97 mg/g) was detected when compared with conventional LDH-1 (0.90 mg/g). Therefore, the novel approach for the engineering of meta-aluminate intercalated mafic hydrotalcite not only introduces facile and practical procedures, but also furnishes a much more efficient adsorption system. In the matter of structure durability, the as-synthesized LDH-2 presented exceptional resistance, maintaining activity after five consecutive cycling runs. This investigation sheds light on the facile and affordable synthesis of the LDH construction.

Elucidating the Mechanism of Self-Healing in Hydrogel-Lead Halide Perovskite Composites for Use in Photovoltaic Devices.

Since the emergence of organometal halide perovskite (OMP) solar cells, there has been growing interest in the benefits of incorporating polymer additives into the perovskite precursor, in terms of both photovoltaic device performance and perovskite stability. In addition, there is interest in the self-healing properties of polymer-incorporated OMPs, but the mechanisms behind these enhanced characteristics are still not fully understood. Here, we study the role of poly(2-hydroxyethyl methacrylate) (pHEMA) in improving the stability of methylammonium lead iodide (MAPI, CH3NH3PbI3) and determine a mechanism for the self-healing of the perovskite-polymer composite following exposure to atmospheres of differing relative humidity, using photoelectron spectroscopy. Varying concentrations of pHEMA (0-10 wt %) are incorporated into a PbI2 precursor solution during the conventional two-step fabrication method for producing MAPI. It is shown that the introduction of pHEMA results in high-quality MAPI films with increased grain size and reduced PbI2 concentration compared with pure MAPI films. Devices based on pHEMA-MAPI composites exhibit an improved photoelectric conversion efficiency of 17.8%, compared with 16.5% for a pure MAPI device. pHEMA-incorporated devices are found to retain 95.4% of the best efficiency after ageing for 1500 h in 35% RH, compared with 68.5% achieved from the pure MAPI device. The thermal and moisture tolerance of the resulting films is investigated using X-ray diffraction, in situ X-ray photoelectron spectroscopy (XPS), and hard XPS (HAXPES). It is found that exposing the pHEMA films to cycles of 70 and 20% relative humidity leads to a reversible degradation, via a self-healing process. Angle-resolved HAXPES depth-profiling using a non-destructive Ga Kα source shows that pHEMA is predominantly present at the surface with an effective thickness of ca. 3 nm. It is shown using XPS that this effective thickness reduces with increasing temperature. It is found that N is trapped in this surface layer of pHEMA, suggesting that N-containing moieties, produced during reaction with water at high humidity, are trapped in the pHEMA film and can be reincorporated into the perovskite when the humidity is reduced. XPS results also show that the inclusion of pHEMA enhances the thermal stability of MAPI under both UHV and 9 mbar water vapor pressure.

Hierarchically arranged γ-NiOOH/β-FeOOH layer supported on modified Molybdenum-BiVO4 thin film for oxygen evolution reaction

Due to the slow kinetics of water oxidation, severe surface charge recombination is a significant energy loss that impedes efficient photoelectrochemical performance. Constructing a scheelite bismuth vanadate (BiVO4) electrode with an oxygen evolution catalyst and doping is an effective way to increase the performance of water oxidation. Importantly, this attempt avoids any sacrificial agents and binders. Using a single-step hydrothermal-based method, a nickel-iron (oxy)hydroxide is deposited unlike conventional two-step photoelectrodeposition method onto the surface of BiVO4 doped with 2% molybdenum dopant. Through this method, the as-formed nickel-iron (oxy)hydroxide is in γ-NiOOH and β-FeOOH forms. The difficulty of transporting charge carriers-hole pairs along the BiVO4 is reduced by incorporating molybdenum. A low-cost but efficient co-catalyst, nickel-iron (oxy)hydroxide is introduced to surpass the charge recombination on BiVO4. A comparison of photocurrent density-voltage and photocurrent density-time curves with and without an oxygen evolution catalyst reveals that nickel-iron (oxy)hydroxide accelerates the anodic photocurrent of the BiVO4 from ∼1 to 5 mA cm−2 (1.23 V vs. RHE). Simultaneously, the molybdenum-doped BiVO4 layer with a small band gap and extremely good photoelectrostability and the (oxy)hydroxide layer with good conductivity provide synergetic enhancement of both stability over 12 hours and photocurrent density.

A hybrid of MIL-53(Fe) rhombus and conductive CoNi2S4 nanosheets as a synergistic electrocatalyst for the oxygen evolution reaction.

Hydrogen energy is considered to be a zero-carbon chemical energy alternative to traditional fossil energy, and electrolysis of water, as one of the most effective methods of producing hydrogen, can produce high-purity hydrogen under the premise of zero pollution. The oxygen evolution reaction (OER) is a slow and energy-intensive four-electron process that limits the rate of decomposition of electrolyzed water and is considered as the bottleneck for overall water splitting. In this paper, CoNi2S4 nanosheets were assembled on blank nickel foam with a conventional two-step hydrothermal method, which then was continued with a hydrothermal method to load the diamond-block structure of MIL-53(Fe) on top of CoNi2S4 nanosheets, denoted as MIL-53(Fe)@CoNi2S4/NF. The MIL-53(Fe)@CoNi2S4/NF catalyst exhibited excellent electrochemical performance in 1 M KOH aqueous solution, which required an overpotential of only 201 mV when the current density reached 20 mA cm-2. In addition, after long-term stability testing, the MIL-53(Fe)@CoNi2S4/NF catalyst maintained its favourable OER activity due to the lattice structure of the rhombic blocks which enhanced both the stability of the catalyst structure and the internal ion transport channels.

Rapid lignin quantification for fungal wood pretreatment by ATR-FTIR spectroscopy

Lignin determination in lignocellulose with the conventional two-step acid hydrolysis method is highly laborious and time-consuming. However, its quantification is crucial to monitor fungal pretreatment of wood, as the increase of acid-insoluble lignin (AIL) degradation linearly correlates with the achievable enzymatic saccharification yield. Therefore, in this study, a new attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy method was developed to track fungal delignification in an easy and rapid manner.Partial least square regression (PLSR) with cross-validation (CV) was applied to correlate the ATR-FTIR spectra with the AIL content (19.9 %–27.1 %). After variable selection and normalization, a PLSR model with a high coefficient of determination (RCV2 = 0.87) and a low root mean square (RMSECV = 0.60 %) were obtained despite the heterogeneous nature of the fungal solid-state fermentation. These results show that ATR-FTIR can reliably predict the AIL content in fungus-treated wood while being a high-throughput method. This novel method can facilitate the transition to the wood-based economy.

Influence of a Two-Dimensional Growth Mode on Electrical Properties of the GaN Buffer in an AlGaN/GaN High Electron Mobility Transistor.

An extensive study has been conducted on a series of AlGaN/GaN high electron mobility transistor (HEMT) samples using metalorganic vapour phase epitaxy, to investigate the influence of growth modes for GaN buffer layers on device performance. The unintentional doping concentration and screw dislocation density are significantly lower in the samples grown with our special two-dimensional (2D) growth approach, compared to a widely-used two-step method combining the 2D and 3D growth. The GaN buffer layers grown by the 2D growth approach have achieved an unintentional doping density of 2 × 1014 cm−3, two orders lower than 1016 cm−3 of the GaN samples grown using a conventional two-step method. High-frequency capacitance measurements show that the samples with lower unintentional doping densities have lower buffer leakage and higher breakdown limits. This series of samples have attained sub-nA/mm leakages, a high breakdown limit of 2.5 MV/cm, and a saturation current density of about 1.1 A/mm. It indicates that our special 2D growth approach can effectively lessen the unintentional doping in GaN buffer layers, leading to low buffer leakage and high breakdown limits of GaN/AlGaN HEMTs.

Improved macroscopic depletion in 2-D nodal analysis by 2x2 albedo-corrected parameterized equivalence constants method

This work introduces a 2x2 albedo-corrected parameterized equivalence constants (APEC) method for the macroscopic depletion of nuclear reactors in 2-D nodal analysis to overcome the inherent limitations of the conventional two-step method. A new 2x2 APEC leakage correction that improves fuel assembly (FA) homogenized group constants (HGCs) with a 2x2 FA subdivision is proposed as an improvement on the previous APEC method correcting the HGCs with a 1x1 FA subdivision. Both burnup-independent and -dependent APEC functions are devised by performing various color-set depletion calculations using a transport lattice code. The APEC method is implemented to an in-house macroscopic depletion nodal code based on the nodal expansion method (NEM). For macroscopic depletion, Xe-135 and Sm-149 transient models are proposed based on simplified Xe-135 and Sm-149 decay chains. In addition to the lattice burnup, power-density is newly introduced as an additional independent parameter in the lattice calculations to consider a history effect in HGCs. Both UOX-loaded and partially MOX-loaded SMR benchmarks are analyzed to assess the performance of the new APEC method. Furthermore, the general applicability of the APEC correction scheme is also evaluated using random variants of the two reference cores, including large-sized PWR problems. Results show that the new burnup-dependent APEC leakage correction can substantially improve the nodal equivalence in terms of the effective multiplication factor and fuel assembly-wise power distribution.

Rheological and Thermal Conductivity Study of Two-Dimensional Molybdenum Disulfide-Based Ethylene Glycol Nanofluids for Heat Transfer Applications

The rheological behavior of two-dimensional (2D) MoS2-based ethylene glycol (EG) nanofluids (NFs) was investigated at low volume concentrations (0.005%, 0.0075%, and 0.01%) in a wide temperature range of 0–70 °C and at atmospheric pressure. A conventional two-step method was followed to prepare NFs at desired volume concentrations. Based on the control rotational (0.1–1000 s−1 shear rate) and oscillation (0.01–1000% strain) methods, the viscoelastic flow curves and thixotropic (3ITT (three interval thixotropic) and hysteresis loop) characteristics of NFs were examined. Shear flow behavior revealed a remarkable reduction (1.3~14.7%) in apparent dynamic viscosity, which showed concentration and temperature dependency. Such remarkable viscosity results were assigned to the change in activation energy of the ethylene glycol with the addition of MoS2. However, the nanofluids exhibited Newtonian behavior at all temperatures for concentrations below 0.01% between 10 and 1000 s−1. On the other hand, strain sweep (@1Hz) indicated the viscoelastic nature of NFs with yielding, which varied with concentration and temperature. Besides, 3ITT and hysteresis loop analysis was evident of non-thixotropic behavior of NFs. Among all tested concentrations, 0.005% outperformed at almost all targeted temperatures. At the same time, ~11% improvement in thermal conductivity can be considered advantageous on top of the improved rheological properties. In addition, viscosity enhancement and reduction mechanisms were also discussed.

Synthesis, Characterization and Properties of Antibacterial Polyurethanes.

Novel physically crosslinked polyurethane (PUII), based on isophorone diisocyanates, was prepared by a conventional two-step method. The chemical structures of the PUII were characterized by fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), scanning electron microscopy (SEM) and DSC. The PUII hydrogels were subjected to solvent-induced self-assembly in THF + water to construct a variety of morphologies. The self-assembly morphology of the PUII was observed by scanning electron microscopy (SEM). The PUII films with different amounts (0.2%, 0.4%, 0.6%, 0.8%, 1.0%) of 1,3,5-Tris(2-hydroxyethyl)hexahydro-1,3,5-triazine (TNO) were challenged with Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Gray mold. The results showed that when a small amount of antibacterial agent were added, the antibacterial effect of films on Botrytis cinerea was more obvious. The mechanical evaluation shows that the antimicrobial polyurethane films exhibit good mechanical properties.

One-step sonochemical fabrication of biomass-derived porous hard carbons; towards tuned-surface anodes of sodium-ion batteries

A facile one-step sonochemical activation method is utilized to fabricate biomass-derived 3D porous hard carbon (PHC-1) with tuned-surface and is compared with the conventional two-step activation method. As raw biomass offers good KOH impregnation, ultrasonication power diffuses both K+ and OH– ions deep into its interior, creating various nanopores and attaching copious functional groups. In contrast, conventional activation lacks these features under the same carbonization/activation parameters. The high porosity (1599 m2/g), rich functional groups (O = 8.10%, N = 0.95%), and well-connected nanoporous network resulting from sonochemical activation, remarkably increased specific capacity, surface wettability, and electrode stability, consequently improved electrochemical performance. Benefiting from its suitable microstructure, PHC-1 possesses superior specific capacity (330 mAh/g at 20 mA/g), good capacity retention (89.5%), and excellent structural stability over 500 sodiation/desodiation cycles at high current density (1000 mA/g). Apart from modus operandi comparison, the two activation methods also provide mechanistic insights as the low-voltage plateau region and graphitic layers decrease simultaneously. This work suggests a scalable and economical approach for synthesizing large-scale activated porous carbons that are used in various applications, be it energy storage, water purification, or gas storage, to name a few.

Heterogeneous treatment effect analysis based on machine-learning methodology.

Heterogeneous treatment effect (HTE) analysis focuses on examining varying treatment effects for individuals or subgroups in a population. For example, an HTE‐informed understanding can critically guide physicians to individualize the medical treatment for a certain disease. However, HTE analysis has not been widely recognized and used, even given the explosive increase of data availability attributed to the arrival of the Big Data era. Part of the reason behind its underuse is that data are often of high dimension and high complexity, which pose significant challenges for applying conventional HTE analysis methods. To meet these challenges, a newly developed causal forest HTE method has been derived from the random forest machine‐learning algorithm. We conducted a systematic performance evaluation for the causal forest method against the conventional two‐step method by simulating scenarios with different levels of complexity for the analysis. Our results show that causal forest outperforms the conventional HTE method in assessing treatment effect, especially when data are complex (e.g., nonlinear) and high dimensional, suggesting that causal forest is a promising tool for real‐world applications of HTE analysis.

Preparation of low-cost perovskite solar cells with high-quality perovskite films in an ambient atmosphere

High-quality perovskite films are extremely crucial to obtain perovskite solar cells with excellent photovoltaic performance, especially for carbon-based hole transport materials (HTM)-free perovskite solar cells. In this work, a facile and low-cost double two-step method (DT-method) is developed to prepare uniform and pinhole-free CH3NH3PbI3 perovskite films in an ambient atmosphere by utilizing the dissolution-recrystallization of PbI2 in DMF. That is to spin-coat PbI2 and CH3NH3I solution sequentially onto pristine perovskite films prepared by the conventional two-step method. The solar cells fabricated by the DT-method show a dramatic performance improvement, including V oc, J sc, and fill factor reach 0.85 V, 15.56 mA cm−2, and 0.58 respectively, which increase power conversion efficiency from 3.93% to 7.58% compared with the conventional two-step method. The improvement in performance and stability of solar cells is mainly due to the higher coverage of perovskite films onto the underlying mesoporous TiO2 layer and a negligible amount of PbI2 residue, which can effectively reduce charge recombination and promote the rapid transfer of charge carriers. In summary, this work presents a process for preparing carbon-based HTM-free perovskite solar cells (PSCs) in a high-humidity atmospheric environment (60%–85%). This simple device structure and preparation condition can greatly reduce the production threshold and cost of PSCs.

Energy, exergy and corrosion analysis of direct absorption solar collector employed with ultra-high stable carbon quantum dot nanofluid

Nanofluid offers remarkable thermal and optical properties favourable for direct solar absorption. The nanofluids prepared by the conventional two-step synthesis method have low colloidal stability, while that synthesized through the one-step method is costly. Hence the nanofluid synthesized using an economical one-step method has great significance. In the present study, a highly stable C-dot/water nanofluid was synthesized using an economical one-pot synthesis method. The optical characterisation, corrosion analysis and cost estimation of the nanofluid were conducted. The influence of C-dot/water nanofluid on the performance of direct absorption solar collector was analyzed. The direct absorption parabolic solar collector employed with C-dot/water nanofluid yielded a maximum thermal efficiency of 73.41% at Reynolds number of 2952, while that for water was 15.79%. Thermodynamic analysis of the system and cost estimation of the nanofluid was performed to establish its commercial suitability in various solar thermal devices. The maximum exergy destruction was found to be 924.3 W and was more or less constant at all flow rates. The main highlight of the new C-dot/water nanofluid is its significantly high colloidal stability and was found to be stable for more than six months. The corrosion rate of the new C-dot/water nanofluid was obtained as 0.094 mm/year, while that for the base fluid was 0.372 mm/year. With superior optical performance, corrosion resistance, and low production cost, the C-dot nanofluid has the potential to be a prospective working fluid in various direct absorption solar thermal systems.

Honeycombed activated carbon with greatly increased specific surface by direct activation of glucose for supercapacitors

In the production of activated carbons (ACs), glucose as a precursor is prone to producing the graphitic char intermediates after carbonization, which are difficult to be activated in the subsequent activation. In order to obtain a desirable specific surface area, either twice activation after carbonization or hydrothermal treatments of glucose before activation is applied. In this research, the direct activation of glucose has been executed to produce honeycombed ACs via deoxygenation of the glucose precursor in the KOH aqueous solution for appropriate time at room temperature. It is found that when glucose is subjected to the alkaline circumstance, dehydration and polymerization reactions increase the C/O ratio while the degradation and oxidation decrease the C/O ratio. The AC from the deoxygenated product with the highest C/O ratio has a superior specific surface area of 1912 m2 g−1 which is much higher than 130 m2 g−1 for the AC by the conventional two-step method. The Honeycombed morphology and the specific surface increased by one order of magnitude lead to good performance of 268 F g−1 in the KOH and 24.5 Wh kg−1 in the KBr electrolyte.

One-pot in situ synthesis of Cu-SAPO-34/SiC catalytic membrane with enhanced binding strength and chemical resistance for combined removal of NO and dust

The SiC catalytic membrane combining dust removal and denitration can realize the efficacious treatment of atmospheric pollutants. Unfortunately, a large amount of SiO2, formed by the partial oxidation of SiC at a high temperature, results in the decreased chemical resistance of SiC catalytic membrane. In addition, the complicated preparation processes and susceptible to loss of catalytic components under harsh conditions restrict the industrial application of SiC catalytic membranes. Here, the Cu-SAPO-34(D)/SiC catalytic membranes were directly prepared via a facile one-pot hydrothermal synthesis method, which ingeniously utilized the generated SiO2 as a Si source to participate in the growth of Cu-SAPO-34 zeolites. Excellent binding strength and chemical resistance were simultaneously realized for the SiC catalytic membranes. As a comparison, a Cu-SAPO-34(I)/SiC catalytic membrane was fabricated via the conventional two-step ion-exchange method. The 0.2 Cu-SAPO-34(D)/SiC (Cu molar ratio of 0.2) achieved the best NH3-SCR performance among the prepared catalytic membranes for its highly active copper and oxygen species, abundant Lewis acid sites and remarkable redox capacity. When implementing the simultaneous removal of NO and PM, the 0.2 Cu-SAPO-34(D)/SiC catalytic membrane achieved a high NO degradation performance of 98% from 200 to 280 °C, coupled with an excellent PM0.3 (model dust with average size of 300 nm) filtration performance of 99.99%. These results were better than those of the Cu-SAPO-34(I)/SiC catalytic membrane (92% for NO degradation and 99.98% for PM0.3 filtration). The one-pot in situ synthesis of Cu-SAPO-34(D)/SiC catalytic membrane with enhanced binding strength and chemical resistance provides a novel strategy for preparation of high-performance SiC catalytic membrane with double benefits.

A New Approach for Controlling Mesoporosity in Activated Carbon by the Consecutive Process of Air Oxidation, Thermal Destruction of Surface Functional Groups, and Carbon Activation (the OTA Method).

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO2 gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm3/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m2/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm3/g (33.0% of total pore volume) and surface area of 1499 m2/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.