Alkaline Solution Research Articles

Highly efficient and selective removal of 90Sr by the carboxylated COFs (Tp-DTA) from radionuclides-contaminated groundwater

In this study, a carboxyl-functionalized covalent organic framework (COF) rich in nitrogen (N) and oxygen (O) functional groups was prepared and characterized, which provided a new opportunity for the efficient and rapid treatment of radioactive contamination in nuclear wastewater. The synthesis of the COF (Tp-DTA) was constructed using 1,3,5-triformylphloroglucinol (TFP) and 2,5-diaminoterephthalic acid (DTA), providing a large specific surface area, mesoporous pore, and abundant coordination sites with high adsorption capacity and exceptional affinity for Sr2+. Batch adsorption experiments exhibited that Tp-DTA achieved a maximum adsorption capacity of 145.4 mg/g for Sr2+ in alkaline solutions, reaching adsorption equilibrium within 60 min. Tp-DTA exhibited rapid kinetics for 90Sr, with the amounts of 90Sr removed more than 95% within 3 min. In the presence of coexisting ions (Na+, K+, Cs+, Mg2+, and Ca2+), Tp-DTA displayed excellent preferential selectivity for Sr2+ and high removal efficiency. Even in simulated groundwater containing multiple complex ions, Tp-DTA demonstrated a strong affinity for Sr2+ and showed practical applicability with a nearly 100% removal efficiency for 90Sr. XPS and FTIR characterizations confirmed that the adsorption mechanism of Sr2+ involved chelation exchange between the carboxyl groups of Tp-DTA and Sr2+ in the solution. Furthermore, the desorption efficiency of HCl (>0.01 mol/L) can reach 95% and five cyclic desorption-adsorption experiments demonstrated the reusability of Tp-DTA, endowing the carboxyl-functional COF with great potential in the treatment of 90Sr-contaminated radioactive wastewater and environmental remediation.

Mechanical and frictional properties of coconut husk powder reinforced polymer immersed in a simulated acidic medium for oil/gas applications

Polymeric materials are constantly exposed to aggressive environments, negatively impacting their mechanical and chemical properties. In salt, acid, or alkaline solutions, polymer materials degrade due to surface flaws, microcracks, or other irregularities. For the first time, this study considers the behaviour of coconut powder/coir-reinforced synthetic LDPE hybrid composite immersed in an aggressive (acidic) medium for 15, 30 and 45 days. The structural, mechanical, and frictional behaviour of the developed coir/coconut husk powder/LDPE hybrid composites were measured after ageing in hydrochloric acid (HCl) as potential materials for oil and gas applications. From the XRD patterns, the prominent reflections in the control samples increased with the acid ageing days, while less prominent reflections characterized the hybrid composites. The hardness of the reinforced samples immersed for 30 and 45 days (30B and 45A) showed the highest values of 0.28 Hv, while the control samples immersed for 15 days had the least hardness. The reinforced samples immersed for 15 and 30 days (15B and 30B) showed the lowest and highest fracture toughness, respectively. The control samples were observed to absorb little water after immersion for 144 h. The result showed that although the reinforced hybrid composites showed better mechanical properties, with an increase in the days of immersion in an aggressive medium, the properties became compromised compared to the un-reinforced samples. Hence, the applications of the produced reinforced polymers in the oil and gas industries may be limited.

Effect of pH on the properties of protonated polyaniline‐based films for pH sensing applications

AbstractThe chemical and physical properties of protonated polyaniline (PANI)‐based films, including PANI‐emeraldine salt (ES) and PANI/polyvinyl acetate (PVAc) films, before and after pH treatments are characterized and compared. Protonated PANI‐based films are prepared by spin coating. The effects of pH value and immersion time on the film properties are investigated to gain a better understanding of their performance in pH sensing. The films are characterized based on color, morphology, chemical structure, phase state, and protonation state. Protonated PANI‐based films exhibit a color change from green to dark blue as deprotonation occurs in solutions with higher pH. The highly porous structure of PANI/PVAc films is slightly affected by the pH of the solution. However, the globular structure of the PANI‐ES films forms cracks with increasing immersion time. PANI/PVAc films exhibit better stability in acidic and neutral solutions than in alkaline solutions because of the hydrolysis of PVAc. Compared with the negligible differences in the PANI/PVAc film in buffers with different pH, PANI‐ES exhibits noticeable changes. Therefore, PVAc improves the stability and performance of PANI for pH‐sensing applications.

The influence of nanostructure and electrolyte concentration on the performance of nickel sulfide (Ni3S2) catalyst for electrochemical overall water splitting

Developing non-precious nanostructured electrocatalysts, exhibiting high catalytic activity in combination with excellent stability, has an enormous potential to replace noble-metal-based catalysts for Hydrogen production through electrochemical water splitting. In this study, a facile method is used for the synthesis of three different hierarchical nanostructures of nickel sulfide (Ni3S2) including nanosheets, nanorods, and multiconnected nanorods that are directly grown on 3D nickel foam (NF). These nanostructured electrocatalysts are evaluated for electrochemical water splitting in alkaline media using four different concentrations to understand the effect of nanostructure and ion concentration on the efficiency. Among different combinations of structure and electrolyte concentration, the Ni3S2 in the form of nanosheets exhibited the best electrocatalytic performance for hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER) in 3.0 M alkaline solution. The hierarchical Ni3S2 nanosheets exhibited a high electrochemically active surface area, which facilitated the charge transport phenomenon along the electrode–electrolyte interface in a higher electrolyte concentration that improved the reaction kinetics so as overall water splitting. The developed Ni3S2 nanosheets required an overpotential of 110 mV (@10 mA cm−2) and 211 mV (@100 mA cm−2) for HER and OER, respectively in 3.0 M electrolyte concentration. This work provides insight into how the materials’ nanostructures and electrolyte concentration could be utilized to improve the electrocatalytic performance for an overall water-splitting process, and the concept could be applied for material designing and conditions optimization for other catalytic applications.

Smart release of turmeric as a potential corrosion inhibitor from a pH-responsive polymer encapsulated highly ordered mesoporous silica containers

This study reports on the loading of corrosion inhibitors like benzotriazole (organic), tartrazine, and turmeric (green) into highly ordered mesoporous silica containers encapsulated with a pH-responsive polymer poly(diallyldimethylammonium chloride) (PDDA) for the smart and sustained release. The incorporation and encapsulation of green corrosion inhibitors, release kinetics and its inhibition efficiency is not studied yet. The synthesised containers had a mesoporous micro-rod-like structure with a pore size of 7 nm and a high surface area of 514.26 m2/g. The pH-responsive behaviour of the PDDA encapsulating polymer is confirmed by monitoring the release of the inhibitors in neutral and alkaline solutions using UV–Visible spectroscopy. The corrosion inhibition performance and its mechanism are evaluated in an alkaline environment containing 0.1 M NaCl using electrochemical impedance spectroscopy over a period of 168 h on mild steel. Among the studied corrosion inhibitors, turmeric showed a maximum of 85.4 % inhibition efficiency after 1 h of immersion. However, SBA-15-Turmeric-PDDA exhibited a higher Rp value of 0.96 kΩ cm2 compared to only turmeric after 168 h of exposure. The smart release of turmeric and silica adsorption showed enhanced corrosion protection, which can be used for various industrial applications.

Lignin/mesoporous hollow silica nanosphere thin film nanocomposite loose nanofiltration membrane for dye/salt separation

It has been still expected to explore a green and low-cost raw material for fabricating high performance loose nanofiltration (LNF) membrane with high permeance and dye/salt selectivity. In this report, aminated mesoporous hollow silica (AHS) nanospheres are first synthesized. Then, a lignin-based LNF membrane is fabricated employing aminated lignin as raw material, trimesoyl chloride as a crosslinker, and AHS nanospheres as nano additives by interfacial polymerization. It shows excellent pure water permeance, high dye rejection, and salt permeation. After being modified with L-arginine, the PWP (49.9 LMH bar−1) and salt permeation are further improved. Simultaneously, the dye rejections are kept at a high level. The AHS nanospheres provided abundant water/salt diffusion channels for the lignin-based separation layer. The hollow structure of the nanospheres decreases the diffusion resistance of the water and salt. Moreover, the membrane shows satisfactory structural and separation performance stability during immersion in acid and/or alkaline solutions. After being treated with 5500 ppm h chlorination strength, it still exhibits excellent BBR/NaCl selectivity accompanied by a small permeance increase. Furthermore, the membrane shows excellent fouling resistances, satisfactory bactericidal (92.5 %) and bacterial anti-adhesion properties. The membrane shows excellent performance stability in a long-term (80 h) dye/salt separation process.

Anionic extracellular polymeric substances extracted from seawater-adapted aerobic granular sludge.

Anionic polymers, such as heparin, have been widely applied in the chemical and medical fields, particularly for binding proteins (e.g., fibroblast growth factor 2 (FGF-2) and histones). However, the current animal-based production of heparin brings great risks, including resource shortages and product contamination. Recently, anionic compounds, nonulosonic acids (NulOs), and sulfated glycoconjugates were discovered in the extracellular polymeric substances (EPS) of aerobic granular sludge (AGS). Given the prevalence of anionic polymers, in marine biofilms, it was hypothesized that the EPS from AGS grown under seawater condition could serve as a raw material for producing the alternatives to heparin. This study aimed to isolate and enrich the anionic fractions of EPS and evaluate their potential application in the chemical and medical fields. The AGS was grown in a lab-scale reactor fed with acetate, under the seawater condition (35 g/L sea salt). The EPS was extracted with an alkaline solution at 80 °C and fractionated by size exclusion chromatography. Its protein binding capacity was evaluated by native gel electrophoresis. It was found that the two highest molecular weight fractions (438- > 14,320 kDa) were enriched with NulO and sulfate-containing glycoconjugates. The enriched fractions can strongly bind the two histones involved in sepsis and a model protein used for purification by heparin-column. These findings demonstrated possibilities for the application of the extracted EPS and open up a novel strategy for resource recovery. KEY POINTS: • High MW EPS from seawater-adapted AGS are dominant with sulfated groups and NulOs • Fifty-eight percent of the EPS is high MW of 68-14,320 kDa • EPS and its fractions can bind histones and fibroblast growth factor 2.

NiCoMnS/rGO nanocomposite for enzyme-free and ultrasensitive electrochemical catalysis of hydrogen peroxide and glucose

It is attractive to develop non-noble-metal nanomaterials with large surface area and good conductivity as a high-active catalyst electrode for molecular detection in electrochemical sensors. In this work, we successfully fabricated NiCoMnS/rGO by one-step hydrothermal method, which showed good peroxidase-like activity in an acidic environment. The NiCoMnS/rGO modified electrode exhibited excellent enzyme-free electrochemical catalysis performance for hydrogen peroxide (H2O2) reduction in acidic solutions and glucose oxidation in alkaline solutions. For the detection of H2O2, this electrochemical sensor displayed a wide linear range from 10.0 μM to 7.5 mM with a low limit of detection of 1.1 μM. As for glucose, it also showed a wide linear range from 50.0 μM to 1.3 mM with a low limit of detection of 1.0 μM. Moreover, it had good stability and reproducibility. It was also used for the determination of H2O2 and glucose in real samples. This nanomaterial held great promise as an enzyme-free sensing platform toward H2O2 and glucose detection.

Amphiphilic Azo-Functionalized Polyhedral Oligomeric Silsesquioxane; Synthesis and Photo-Switched Efficient Phase Transfer via Host-Guest Encapsulation.

A new amphiphilic azo-functionalized polyhedral oligomeric silsesquioxane (POSS) derivative was synthesized by functionalizing octa(3-aminopropyl)silsesquioxane (OAS-POSS) with 4-((4-(dodecyloxy)phenyl)diazenyl)benzoic acid, affording a hydrophilic amino POSS head and hydrophobic dodecyl tail with a diphenyl-azo connector. Prepared amphiphilic azo-functionalized POSS (azo-POSS) exhibited high ability for encapsulation and transferring cationic dyes into the organic phase by vigorously mixing with aqueous solutions of each dye. The photo-controlled encapsulating properties of the synthesized phase transfer reagent was studied using cationic dyes, such as methylene blue (MB), crystal violet (CV) and thymol blue in acidic conditions. Results showed more than 95 % encapsulation of MB. However, no considerable encapsulation was shown in the case of anionic dyes such as eriochrome black T (EBT) and thymol blue in alkaline solutions. By trans/cis isomerization of the azo moiety of the phase transfer reagent by UV irradiation (365 nm), the amount of dye encapsulation was decreased, which could be attributed to the formation of cis isomer that led to the folding of the dodecyl alkyl tail on the POSS moiety, and therefore prevent to lay the 3-aminopropyl moieties of POSS head to the water/DCM interface to adsorb and encapsulate MB molecules.

Precisely tuning the Ni3N/Pt interface to boost the catalytic activity of alkaline hydrogen evolution reaction

The hydrogen evolution reaction (HER) in alkaline solutions does not access H* directly, resulting in a slower reaction kinetics compared to that in acidic solutions. Here, we report a Cr-doped Ni3N/Pt heterostructure that provides additional active sites to produce H* via the water-cleaving step, in addition to the intrinsic active Pt site for H* absorption. It is demonstrated that the Cr dopant can modulate the charge redistribution between Ni3N and Pt interface, lowering the energy barrier of both the Volmer step and the following Heyrovsky step. As a result, the prepared Cr-Ni3N/Pt catalyst achieves an extreme low overpotential of 20 mV to deliver a current density of 10 mA/cm2 under alkaline conditions, which is significantly better than the commercial Pt/C catalyst (45 mV). Density Functional Theory (DFT) further reveals that the Cr-modified Ni3N/Pt interface undergoes electronic orbital hybridization, enhancing the water adsorption and dissociation processes on the Ni sites. This work presents the feasibility of the electronic structure modulation in low-platinum catalysts, which provides an effective strategy for the design of electrocatalysts used in multi-step reactions.

Experimental study and prediction on tensile behavior of steel fiber-reinforced-carbon/glass hybrid composite bars in concrete environment

The tensile behavior of steel fiber-reinforced-carbon/glass hybrid composite bars (S-CG HCBs) in concrete environment was experimentally investigated. The influences of the steel fiber content (VS) and the carbon-glass ratio (VC/VG) on the tensile behavior of corroded S-CG HCBs were analyzed. The optical microscope (OM) was used to reveal the morphology and corrosion mechanism of S-CG HCBs. The results show that under tensile load, S-CG HCBs exhibited a pseudo-yield platform due to the separate fracture of the three types of fibers and the buckling of steel fibers. The retentions of yield and ultimate strengths of the S-CG HCBs in alkaline solution increased with the VS or VC/VG increased due to the reduction of glass fiber content and its more inferior alkali resistance than carbon and steel fibers. After 63 days of corrosion at a 40 ℃, the specimen (S30C1G6), whose VS and VC/VG are 30% and 1/6, respectively, exhibited the highest tensile strength retention rate of 87.88% compared to other specimens. In addition, the tensile stress retention of S-CG HCBs serviced in concrete environment under various ambient temperatures was predicted based on the Arrhenius equation.

Enhancing reactivity of granite waste powder toward geopolymer preparation by mechanical activation

Granite waste powder (GWP) is a solid waste produced during stone processing, and its accumulation has brought serious environmental and ecological problems. Due to its rich Si and Al components, GWP is a potential raw material for the preparation of geopolymers, but its low reactivity limits its utilization. This study aimed to enhance the reactivity of GWP toward geopolymer preparation by mechanical activation. During mechanical activation, the particle size of GWP decreased rapidly, and its internal pore volume gradually increased, which made its specific surface area continuously increase. The relative crystallinity of the main mineral phases in GWP decreases continuously with mechanical activation, and the aluminosilicate minerals (including albite, microcline, and biotite) are more easily amorphized than quartz. Leaching tests show that activated GWP can dissolve higher percentages of silicon and aluminum components in alkaline solutions. After 120 min of activation, the dissolution percentage of Si increased from 1.55% to 6.25%, and that of Al increased from 4.83% to 20.86%. The reaction heat result shows that the early geopolymerization involving activated GWP releases higher cumulative heat, which reflects a higher degree of reaction. Also, geopolymer incorporated with activated GWP, its compressive strength increased from 50.83 MPa to 78.94 MPa, and its flexural strength increased from 7.2 MPa to 10.0 MPa. These results confirmed that the reactivity of GWP can be significantly enhanced by mechanical activation. This technology may provide an efficient and promising method to improve the reactivity of GWP and promote its utilization in the preparation of geopolymers.

Surface-sulphurated nickel–molybdenum alloy film as enhanced electrocatalysts for alkaline overall water splitting

Nickel-molybdenum (NiMo) alloys are a kind of promising HER electrocatalysts to supersede precious metal based materials due to their highly active hydrogen evolution reaction (HER) kinetics in alkaline solution. However, the poor stability of NiMo, caused by the Mo dissolution mainly due to the thermodynamically instability of Mo in alkaline media, significantly limits its practical applications. Herein, a facile strategy is developed to modify the surface of the electrodeposited NiMo alloy film via a simple surface sulphuration treatment. Material characterizations show that the NiS homogeneously covers the surface of the NiMo alloy, resulting in a NiS/NiMo heterostructure. Electrochemical measurements show that the NiS/NiMo heterostructure exhibits outstanding HER activity (η-10 mA cm-2 = 77 mV) and good stability for 24 h stability test. Surprisingly, the heterostructure also displays excellent OER kinetics by delivering an ultra-low overpotential of 245 mV (10 mA cm−2). The constructed electrolyzer with NiS/NiMo acted as both cathode and anode needs only 1.547 V to power the water splitting at 10 mA cm−2. The formation of heterostructure and the enhanced electrochemically active surface area are responsible for the exceptional HER/OER electrocatalytic performance. This work offers a simple way to build sulfide/alloy heterostructures to improve the electrocatalytic activity of electrocatalysts.

An electrochemical catalyst of CUST-581 for methanol oxidation and hydrogen peroxide detection

A new Ni-MOF(CUST-581), [(Ni)2(BIMB)1.5(BTB)] [CUST-581, H3BTB = 1,3,5-tris(4-carboxyphenyl)benzene, BIMB = 1,4-bis((1H-imidazolyl)methyl)benzene], was synthesized using the solvothermal method. CUST-581 exhibited not only high current density but also long-term electrochemical stability during the measurement of methanol oxidation reactions. Moreover, CUST-581 was used as an enzyme-free electrochemical sensing platform for the determination of H2O2. The electrochemical sensing performance of the CUST-581 modified glassy carbon electrode for H2O2 was evaluated by cyclic voltammogram and time measurements in alkaline solutions. The sensor showed a good linear range (20 μM-5000 μM), a low detection limit of 0.28 μM, high sensitivity (0.37 mA mM−1 cm−2) and fast response. Importantly, good reproducibility and repeatability, long time stability and excellent selectivity were obtained in the fabricated H2O2 sensor. The results of the actual samples suggest that the Ni-MOF/GCE sensor could be a promising candidate for H2O2 sensing applications.

In situ synthesis of Fe2O3/Fe3O4 nanoarray hybrid as highly effective electrocatalysts for alkaline hydrogen evolution

It is of great importance to rationally develop and design cost-effective, high durable and non-noble metal catalysts for electrocatalytic water splitting. Here, self-supported well-defined crystalline iron oxides hybrid (FeOx/IF) was successfully fabricated by facile in-situ thermal air oxidation of iron foam. An investigation into the effects of thermal oxidation temperature on the crystalline structure and surface appearance of FeOx/IF was studied. The resultant FeOx/IF-550 reveals nanoarrays morphology composed of Fe2O3 and Fe3O4 hybrid with Fe2O3 and Fe3O4 heterojunctions, which exhibits remarkably superior catalytic activity towards HER with a low overpotential of only 98 mV to drive a current density of 10 mA cm−2 in alkaline solution. Meanwhile, FeOx/IF-550 exhibits good durability with negligible attenuation of overpotential at a large current density of 500 mA cm−2 for 24 h in alkaline solution. The excellent HER performance of FeOx/IF is mainly attributed to the synergistic effect of Fe2O3 and Fe3O4, increased accessible active sites and accelerated charge transfer. The present study provides new insights into the design of cost-effective electrocatalysts with high activity and excellent stability for industrialization.

Electrochemical Investigation of Chloride Ion-Induced Breakdown of Passive Film on P110 Casing Steel Surface in Simulated Pore Solution: Behavior and Critical Value Determination

In the petroleum industry, the casing steel is fixed with a cement sheath to ensure reliable service in demanding conditions characterized by high temperature, high pressure, and exposure to multiple types of media. After the hydration of the cement, a porous material is produced with a highly alkaline solution filling the pores, commonly referred to as the pore solution. The casing will form a protective passive film when in contact with a highly alkaline pore solution. Nevertheless, once the cement sheath cracks, chloride ions in the stratum will pass through the cement sheath to the surface of the casing. When chloride ions accumulate to a certain concentration, the passive film will be destroyed, without exerting a protective influence on the substrate. After chloride ions come into direct contact with the casing, the casing is prone to severe failure due to corrosion perforation. The casing failure can cause a blowout outside the casing and even scrapping of the oil well. Controlling casing corrosion and ensuring casing integrity relies on understanding the critical chloride ion concentration that can cause the degradation of the passive film. Therefore, to assess the electrochemical properties and analyze the damage process of the passive film under varying chloride ion concentrations, several characterization techniques were employed. These included potential–time curves (E-t), polarization curves, electrochemical impedance spectroscopy (EIS), and Mott–Schottky curves. In addition, the composition of the passive film on the surface of the P110 casing steel was qualitatively analyzed using X-ray photoelectron spectroscopy (XPS). To further understand the surface morphology of the P110 casing steel, scanning electron microscopy (SEM) was used.

Effect of Adsorbed Carboxylates on the Dissolution of Boehmite Nanoplates in Highly Alkaline Solutions.

Understanding the dissolution of boehmite in highly alkaline solutions is important to processing complex nuclear waste stored at the Hanford (WA) and Savannah River (SC) sites in the United States. Here, we report the adsorption of model carboxylates on boehmite nanoplates in alkaline solutions and their effects on boehmite dissolution in 3 M NaOH at 80 °C. Although expectedly lower than at circumneutral pH, adsorption of oxalate occurred at pH 13, with adsorption decreasing linearly to 3 M NaOH. Classical molecular dynamics simulations suggest that the adsorption of oxalate dianions onto the boehmite surface under high pH can occur through either inner- or outer-sphere complexation mechanisms depending on adsorption sites. However, both adsorption models indicate relatively weak binding, with an energy preference of 1.26 to 2.10 kcal/mol. By preloading boehmite nanoplates with oxalate or acetate, we observed suppression of dissolution rates by 23 or 10%, respectively, compared to pure solids. Scanning electron microscopy and transmission electron microscopy characterizations revealed no detectable difference in the morphologic evolution of the dissolving boehmite materials. We conclude that preadsorbed carboxylates can persist on boehmite surfaces, decreasing the density of dissolution-active sites and thereby adding extrinsic controls on dissolution rates.

Surface and bulk transformations of Ag2CuMnO4 delafossite during the interaction with CO+O2 mixture

Ternary oxide of silver, copper and manganese (Ag2CuMnO4) with delafossite-type structure demonstrates excellent catalytic activity in the reaction of CO oxidation at room temperature and even below. To prepare delafossite-based catalyst the hydrothermal approach using metal nitrates in alkaline solution with an excess of peroxodisulphate was applied. X-ray diffraction pattern of Ag2CuMnO4 particles was successfully simulated taking into an account crystallite shape anisotropy, particle size distribution, the presence of stacking faults, and the lattice expansion along c axis. As-prepared Ag2CuMnO4 sample was characterized by the presence of Ag1+-, Cu2+- and Mn4+-like surface species predominantly. In situ XRD data revealed the thermal stability of delafossite-type structure in catalytic CO+O2 mixture up to 500 °C, while ex situ XPS showed an evident reorganization of Ag2CuMnO4 surface at markedly lower temperatures (200–250 °C). Heating in CO+O2 medium at 150–400 °C also resulted in significant catalytic activation of Ag2CuMnO4 owing to the Mn enrichment and optimization of manganese and copper electronic exchange. The low-temperature activity of Ag2CuMnO4 catalyst in CO+O2 reaction was proposed to be mainly provided by redox transitions with the participation of Cu1+/Cu2+ and Mn3+/Mn4+ couples, while the catalytic role of silver species is considered as auxiliary only. The innovation point of this work is related to the investigation of the dynamics of surface and bulk structure transformations in connection with the catalytic activation of delafossite particles for the low-temperature oxidation.

Promotion effect of epoxy group neighboring single-atom Cu site on acetylene hydrochlorination

Carbon materials have been used as the support for catalysts in the field of acetylene hydrochlorination, the influence of inevitable oxygen-containing moieties on the reaction is often ignored and the mechanism of the oxygen-doping structure remains ambiguous. Herein, we explored the effect of the oxygen-containing group (COC) in the support on the activity of single-atom dispersed Cu catalysts. By immersing the Cu single-atom catalyst in an alkaline solution, the epoxy species on the carbon support was cleaved to obtain a pure ether species while the Cu site was modified to a more electron-deficient state. The turnover frequency value of Cu/O-FLP catalyst with epoxy groups was 1.6-fold higher than that of alkaline treated catalyst. Our result indicated that the epoxy groups could assist adjacent single-atom Cu sites to synergistically promote the adsorption and cleavage of the reactant hydrogen chloride toward form COH and CuCl bonds, and reduce the reaction energy barrier. The presence of electron deficient Cu sites and ether species could induce competitive adsorption of the acetylene and hydrogen chloride, thereby reducing the activity of the catalyst. This study highlights the influence of surface oxygen species and the tunability of the support, providing the foundation for the fabrication of higher-activity Cu catalysts for acetylene hydrochlorination.

Ultrasonic treatment duration: A nuanced parameter in synthesis affecting structural properties and ORR performance of KOH-activated carbon

In this study, we investigate the effects of the duration of ultrasonic treatment during the impregnation process of a carbon precursor with an aqueous alkaline solution on the structural and electrochemical properties of KOH-activated carbon materials. Our findings using polyacrylonitrile (PAN)-derived carbon materials reveal that extended ultrasonic treatment leads to a more consistent distribution of the activating agent, promoting more uniform surface activation. This leads to notable shifts in the material's structure and surface chemistry, thereby influencing its functionality as an electrode material in supercapacitors and its electrocatalytic activity in the oxygen reduction reaction (ORR). Our results indicate a 6 % difference in the specific surface area and an 8 wt% rise in oxygen content when comparing samples without ultrasonic treatment to those treated for 10 min. Moreover, the specific capacitance increases from 133.9 to 163.5 F g−1, and the ORR activity ascends from 1.88 to 2.23 mA cm−2. This research highlights the potential of ultrasonic treatment duration as a variable to fine-tune the structure and properties of porous carbon materials, emphasizing its scientific and technological significance in the production of stable porous carbon materials.