Different Concentrations Of Phosphoric Acid Research Articles

Effect of Electrolyte Anions on the Activity of Iridium Oxide Catalysts for Water Electrolysis

Developing environmentally friendly and renewable energy sources is essential due to the environmental and energy security issues caused by traditional combustion of fossil fuel-based energy sources. Therefore, as a clean and sustainable energy carrier, hydrogen has attracted great attention in recent years. In this regard, water electrolysis utilizing renewable energy sources to produce hydrogen is considered one of the most promising technologies. It is believed elucidation of the reaction mechanism of highly active iridium oxides is promising for the further development of cost-efficient PEM water electrolysis catalysts. The properties of the MEA could be affected by many parameters such as the catalysts, operating temperature, and pressure1,2. Another important factor is the cation impurities that can be found in the circulating water, which could severely degrade the MEA performance during the operation of a PEM water electrolyze. However, there are less reports on anion impurities such as SO4 2- and PO4 3-. Therefore, in this study, the relationship between electrolyte anions and OER activity was investigated for IrOx catalysts with different crystal structure. By using operando X-ray absorption spectroscopy (XAS), we investigated the electronic state of Ir and O under operation potential.IrOx with different degree of crystallinity (SA3.5 and SA58) were provided by Tanaka Kikinzoku Kogyo K.K., Chemical & Refining Company and named after their BET surface areas. These two samples were then tested for electrochemical properties in different concentrations of phosphoric acid and perchloric acid, respectively. The electrochemical measurements were performed using a standard three-electrode cell connected to an MPG-205-NUC system (Bio-Logic). The cyclic voltammograms (CV) were scanned from 0.1 V to 1.2 V vs. RHE at 50 mV s-1. The electrochemical activities of the catalysts were subsequently investigated using linear sweep voltammetry (LSV) in the range of 1.1 to 1.7 V vs RHE at 10 mV s−1. operando XAS were collected using a home-made flow-type cell, where Pt wire and RHE worked as counter and reference electrodes, respectively. The catalyst ink was coated onto an Nafion membrane to prepare both the X-ray window and working electrode. The electrolyte was circulated at the flow rate of 100 mL min-1.The catalytic performance of IrOx was investigated at different types and content of electrolyte under H3PO4 and HClO4. Figure 1 shows the CVs of SA3.5 and SA58 under different types and content of electrolyte. In the presence of phosphate anions, SA3.5 showed a tendency to decrease Ir redox between 0.6 and 1.1 V with increasing electrolyte concentration. On the other hand, there were no obvious changes in SA58. It was found that IrOx catalysts have an great effect of specific adsorption of anions and low symmetry of monoclinic phase catalysts (SA 3.5) are more susceptible to anion poisoning. Figure 2 shows the result of examining the poisoning mechanism using soft X-ray XAS. O K-edge results present the formation of µ2-O (O-O) bond at around 528.7 eV, which was previously observed by Nong, H. N. et. al. through operando O-K edge measurements during OER process3. The peak intensity at 528.7 eV of the amorphous samples was in the same order as the OER activities. According to potential dependence change of the pre-edge peak, under the presence of phosphate anions, the hole formation to Ir-O hybrid orbitals was suppressed in SA3.5. This result indicates that the anion adsorbs to the active site, poisoning the catalyst surface and inhibiting the reaction. Acknowledgements This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References Zhang, Y.; Zhu, X.; Zhang, G.; Shi, P.; Wang, A.-L.; et al. J. Mater. Chem. A: 2021, 9, 5890-5914.Chen, Z.; Duan, X.; Wei, W.; Wang, S.; Ni, B.-J.; et al. Nano Energy: 2020, 78, 105270.Nong, H. N.; Falling, L. J.; Bergmann, A.; et al. Nature 2020, 587 (7834), 408-413. Figure 1

Efficiency of chemically modified activated carbon derived from banana peel for removal of Pb2+ and Zn2+ from aqueous Solution

Natural and anthropogenic activities generally result to large production of heavy metals. These heavy metals produced are indiscriminately discharged into rivers and other water bodies. Wastewater treatment of industrial effluents become very necessary due to toxic effect of heavy metal pollutants and its indirect effect pose to human health. Banana peel, an agricultural waste biomass can be used to produce bio-sorbent for adsorption of heavy metals from industrial wastewater. This study focused on the production of chemically modified activated carbon using various concentrations of phosphoric acid for removal of lead and zinc metals from aqueous solution. Activated carbon was produced from waste banana peel through thermal pretreatment at temperature of 450℃ preceding chemical modification with different concentrations of phosphoric acid of 0.5 M, 1.0 M and 1.5 M. The three different concentrations of the phosphoric acids represent sample X, Y and Z respectively. To study the adsorption efficiency of chemically modified activated carbon using different concentrations of phosphoric acid, batch experiments were conducted on chemically modified samples to assess the adsorption of lead (II) and zinc metals from aqueous solution. The three adsorbents were interacted with varying parameters such as effect of initial concentration of lead and zinc metal of concentration of 10 mg/L and 2 mg/L respectively. Based on batch experiments conducted, results indicated that adsorbent dose, pH, initial concentration as well as contact time are important factors influencing lead (II) and Zinc metals adsorption from aqueous solutions. Percentage adsorption of lead (II) and zinc metals was above 80 % for all three chemically modified adsorbents investigated. The adsorption capacities of the adsorbents under study showed high adsorption capacity for both zinc and lead metals. This implies that sample X, Y and Z are good adsorbents for adsorption of both zinc and lead metals in an aqueous solution.

Properties and Bifunctional Catalytic Activity of Niobium-Doped Silica-Titania: Effect of Phosphoric Acid Treatment

The effect of phosphoric acid treatment on the physical-chemical properties and catalytic activity of the niobium-doped silica-titania bifunctional catalyst was investigated. As part of the synthesis procedure to produce xPO4−/Nb/TiO2-SiO2, different concentrations of phosphoric acid (H3PO4) were used (x= 0, 0.05, 0.10, 0.15, 0.20, 0.25 M). As shown by XRD analysis, the samples synthesized using 0–0.20 M H3PO4 were in amorphous form, as featureless diffractograms were obtained, indicating the PO4− groups were dispersed homogeneously on the surface of Nb doped SiO2-TiO2. Due to the increased concentration of acid, other compounds were formed in the samples by reactions between PO4− and Nb and/or Ti. Additionally, UV-Vis DRS results indicated that the presence of the PO4− group accelerated the transformation of hydrated tetrahedral Ti species into isolated tetrahedral Ti species. An experimental investigation of the catalytic performance of the catalyst was conducted using 1,2-epoxyoctane as an oxidant for the epoxidation of 1-octene to 1,2-octanediol. It has been demonstrated that H3PO4 treatment was essential for oxidative and acidity active site formation. The current research findings strongly suggested that Nb-doped TiO2-SiO2 treated with 0.2 M H3PO4 was the most effective bifunctional catalyst in generating 1,2-octanediol.

Composition and Properties of Triple Superphosphate Obtained from Oyster Shells and Various Concentrations of Phosphoric Acid.

Triple superphosphates [TSPs, Ca(H2PO4)2·H2O] were produced by exothermic reactions of oyster shells and different concentrations of phosphoric acid (10, 20, 30, 40, 50, 60, and 70% w/w) in a molar ratio of 1:2. The percentage yields, P2O5 and CaO contents, metal impurities, and thermal behaviors of all the as-prepared products are dependent on the concentrations of phosphoric acid added during the production processes, which confirm to get the best optimum of 60% w/w phosphoric acid. All the as-prepared products were characterized by several characterization methods [X-ray fluorescence, thermal gravimetric/derivative thermal gravimetric analysis, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy], verifying that all the obtained compounds are TSP that can be used as fertilizers without metal toxic contaminants. From the successful results, the method for TSP production can be applied in the fertilizer industry based on starting waste materials of oyster shells that can replace the use of unsustainable phosphate or calcium minerals obtained from nonliving things.

Structural and Physico-mechanical Investigations of Mine Tailing-Calcined Kaolinite Based Phosphate Geopolymer Binder

This work explores the possibility of using Mine tailing (MT) as a feedstock in the synthesis of phosphate geopolymer binder. MT was activated at different concentrations of phosphoric acid (4, 6, 8, 10 and 12 M). The modification of the Si/Al weight ratio was done by the incorporation of 5, 10, 15, 20 and 25 wt% of calcined kaolinite (CK). After 28 days of curing, the products obtained were analyzed using XRD, FTIR, compressive strength and water absorption. The results of the XRD and FTIR analyses reveal a partial dissolution of the crystalline phase of iron oxide in this medium and the formation of aluminium phosphate hydrate as new crystalline phase. The optimum values of compressive strength (45.5 MPa) and water absorption (3.0 %) show that the binder obtained by activation with 6 M phosphoric acid and 10 wt% CK incorporation can be used in the manufacture of structural materials. Acid activation of MT thus appears as an innovative way to recycle these fine wastes in the synthesis of geopolymer.

Effect of varying concentrations on the yield of activated carbon produced from African star apple

Activated carbon has been developed using different techniques and activating agents. The activation of carbon is done using different chemical, physical, and bio activating agents. This activating agent gives various outcomes of the activated carbon depending on the structure of the cursor used. The increase in population has also brought about a significant increase in waste generated. In this work, we were able to produce activated carbon from African star apple seed using the seed, husk, and shell. This work was carried out using a furnace at 500 C. The carbon produced was then activated using different concentrations of Phosphoric acid (H3PO4), which are 0.2M, 0.4 M, 0.6 M, 0.8 M and 1.0 M. Whole seed which was impregnated with 0.2 M gave the highest yield of 87.192%. The amount of activating agent used did not determine the yield.

Interaction between phosphorus and zeolite/binder: A realumination study on beta zeolites

Abstract Zeolite/binder (beta/Al2O3) was treated with different concentrations of phosphoric acid, and the samples pre- and post-treatment were characterized by several methods. It was found that the content of tetrahedral framework Al species in the beta zeolite increased after the sample was impregnated with phosphoric acid, and the generated aluminophosphate reduced the external surface area of the catalyst but had no effects on the catalytic ability of the beta zeolite. The realumination behavior of beta zeolite is proposed in this work. Polyphosphate reacted with hexa-coordinated aluminum, resulting in the formation of amorphous aluminophosphate species, which were then transferred to the silicon hydroxyl structure cavity on the zeolite to complete realumination. The influence of the sample before and after phosphoric acid modification on the activity of synthesized polyoxymethylene dimethyl ethers was discussed. When the phosphoric acid concentration was 0.5 M, the time to reach the same conversion of trioxane (about 94%) was shortened by 60 min compared to the parent sample.

Tailoring Chemical, Physical, and Morphological Properties of Sugarcane Bagasse Cellulose Nanocrystals via Phosphorylation Method

ABSTRACT In this work, three different concentrations of phosphoric acid (H3PO4) were used (i.e. 5 M, 8 M, and 11 M) to isolate cellulose nanocrystals (hereafter labeled as 5-PCNC, 8-PCNC and 11-PCNC, respectively) from sugarcane bagasse. The PCNC was analyzed using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). From TEM and XRD results, it was found that the morphology and crystallinity index of the PCNC was influenced by the different concentration of phosphoric acid. FTIR and XPS results indicate that self-interaction of CNC occurs via P–O–P linkages. These data are important for PCNC selection in application; one may consider the aspect ratio (5-PCNC could be a good choice); while other may require higher crystallinity index (8-PCNC and 11-PCNC could be a good candidate).

Phosphoric acid contaminated calcareous soils: Volume change and morphological properties

Contamination of soils is a critical problem as a result of malfunctioning industries like possible leakage and inferior disposal of wastes. The leakage and spillage of acids infiltrate to the ground and cause swelling of the foundations because of their reaction with the active minerals in the soils. Calcareous soils are widely used in construction. Hence, the carbonate soils are liable to volumetric changes when contaminated with acids. The current work examines the effect of the changes of volume as well as the microstructure of calcareous soils when infiltrated by different concentrations of phosphoric acid. The samples of soil were equipped with molds of acid resistance high-density polyethylene. The volume change was measured by the linear variable differential transformer. The compositional analysis was performed for the acid-contaminated samples. The results indicate there is a volume change with varying the acid concentration, however, silty clayey sand exhibited extensive expansion. This can be attributed to the severe reactions of phosphoric acid and carbonate mineral and the products blocked off the passage for the acid to permeate to the other parts of the soil sample as evidenced by the morphological and compositional analysis of the contaminated samples.

Synthesis of composites glauconite/polyaniline doped phosphatic acid and their properties

Polyaniline (PAn) and composites of glauconite/polyaniline (Gl/PAn) were synthesized by chemical oxidation polycondensation of aniline with ammonium peroxodisulfate in aqueous solutions of different concentrations of phosphoric acid, namely 0.60 M or 0.80 M, or 1.65 M, or 3.30 M. The content of glauconite in the reaction mixture was1 g, and the ratio of aniline : glauconite was 1 : 1. The properties of synthesized samples are investigated using by modern physical methods of analysis. The physical analysis of samples properties has been carried out using a Dron-4-07 diffractometer (Cu Kα radiation; l=1.54060 A) in the reflection mode. Fourier-transform infrared (FTIR) spectrа of powders sample were recorded out using a NICOLET IS 10 ATR spectrophotometer in the mode of reflection, which was later transformed into transmission mode. Thermal properties of synthesized samples has been analyzed using Q 1 500-D Derivatograph in the temperature range of 20–900 °C under a heating rate of 10 о /min in the atmosphere of air (corundum crucibles; standard – Al 2 O 3 ; weight of samples – 100 mg). The electrical conductivity of the pelleted samples was determined by measuring their resistance in the sandwich type cells at a temperature of 20±1 о С using a Rigol DM 3 068 set of equipment for resistance measuring. It was found that with increasing by concentration of phosphate acid in the initial reaction mixtures, the crystallinity of polyaniline in samples of pure PAn increases, whereas in samples of composites of Gl/PAn, the polyaniline are preferably amorphous. Intermolecular interaction between the components of the composite is due to the formation of hydrogen bond. Comparison of the results of derivatographic studies showed that the thermal properties of composites depend on the content of glauconite. Thermal stability is higher in samples containing glauconite. It is established that the process of thermodestruction of composites is complex and multistage. Specific electrical conductivity of the received composites of Gl/PAn is less than in PAn samples synthesized at different concentrations of phosphoric acid. Keywords: polyaniline, glauconite, composite materials, structure, thermal analysis, electrical conductivity.

Modeling studies for adsorption of phenol and co-pollutants onto granular activated carbon prepared from olive oil industrial waste

Granular activated carbon (OSAC) which was derived from olive oil industrial solid waste was chemically activated with different concentrations of phosphoric acid. OSAC-materials were evaluated for their ability to remove phenol from aqueous solution in a batch technique. Adsorption isotherms were determined and modeled with five linear Langmuir forms, namely the Freundlich, Elovich, Temkin, Kiselev and Hill-de Boer models. The experimental data for the adsorption of phenol onto OSAM-materials were fitted well with the Langmuir-1 and 2, Freundlich, Kiselev and Hill-de Boer models. Adsorption was carried out on energetically different sites as localized monolayer adsorption and was an exothermic process. The uptake of phenol onto OSAC increased in the following order: OSAC-80%> OSAC-70%> OSAC-60%; the maximum adsorption capacities of phenol were found to be 114.416, 125.628 and 262.467 mg/g onto OSAC-60%, OSAC-70% and OSAC-80%, respectively. On the other hand, OSAC-80% was used as a good adsorbent for the removal of phenol and Cd2+ as co-pollutants from waste aqueous solutions. 80.25% of phenol and 50.66% of Cd2+ can be simultaneously removed by OSAC-80%.

Effect of Crambe abyssinica oil degumming in phosphorus concentration of refined oil and derived biodiesel

Abstract In the present study, the effect of different degumming processes on the phosphorus content of Crambe abyssinica oil and resultant biodiesel was evaluated. The non-edible oil was submitted to water degumming and chemical degumming with different concentrations of phosphoric acid and varying the acid to oil volume percentages. Phosphorus content of the products was measured by UV spectroscopy after sample calcination, according to NP 1994:2000. Biodiesel was produced by transesterification using a 6:1 methanol to oil molar ratio and 1 wt% sodium hydroxide as catalyst at 65 °C, during 1 h. The biodiesel produced directly from the crude oil presented high phosphorus concentration (>20 ppm); consequently, a degumming process was required to fulfil the quality standard (

Selective demineralisation of dentine extrafibrillar minerals—A potential method to eliminate water-wet bonding in the etch-and-rinse technique

ObjectiveThe present study tested the central hypothesis that selective demineralisation of dentine extrafibrillar minerals by lowering the phosphoric acid concentration improves the quality of the resin-dentine interface. MethodsDentine surfaces were etched with different concentrations of phosphoric acid (1, 5, 10, 20, 30 or 40wt%). Scanning electron microscopy was used to observe the micromorphology of the etched dentine surfaces. Energy dispersive X-ray analysis was performed to determine the residual Ca-content of the demineralised dentine matrix. Atomic force microscopy-based nanoindentation was used to analyse the nanomechanical properties of the treated dentine surfaces. The influence of H3PO4 concentration on resin-dentine bond strength was evaluated by microtensile bond strength testing. One-way ANOVA was used to compare the residual Ca-content ratio, reduced elastic modulus (Er) of the treated dentine surfaces and microtensile bond strength among groups. ResultsCollagen fibrils appeared to be wider in diameter after etching with 5% and 10% H3PO4. The partially-demineralized collagen scaffold retained part of its rigidity to maintain an uncollapsed three-dimensional structure. Etching with 1% H3PO4 resulted in the highest residual Ca-content ratio and Er of demineralised dentine matrix, followed by 5% H3PO4. Those values were all significantly higher than values derived from the other groups. Etching with 30% H3PO4 resulted in the lowest Ca-content ratio and Er. Using 5% H3PO4 as etchant resulted in the highest resin-dentine bond strength. ConclusionsSelective demineralisation of the dentine matrix may be achieved by lowering the H3PO4 concentration to 5wt%, to achieve better bonding performance. Clinical relevanceBy retaining intrafibrillar minerals, more through air-drying of the partially demineralised collagen matrix may be accomplished without the need to worry about collapsing a mineral-free collagen matrix during air-drying. This may result in the elimination of water-wet bonding during the application of etch-and-rinse adhesives.

English

The weed Adenocalymma peregrinum that is popularly known in Brazil as “ciganinha”, belongs to the family Bignoniaceae. The only way to control this plant species in crop fields is by the application of herbicides on the stump or directly on the stem. The present study aimed to analyze the effect of glycerine in controlling A. peregrinum (MIERS) L.G.Lohmann when applied on the stem. The glycerin used as a spray application of herbicide, underwent pre-purification processes with different concentrations of phosphoric acid (85%) and was characterized for water content, sulphated ash, total glycerol, matter organic non-glycerol (MONG), methanol and pH. For the analysis of the chemical composition of the stem lignin, holocellulose, extractives, calorific value and elementary quantitative determination of C, N, H, S were determined, as well as the total content of oxygen from the stem. The field work was installed at the town of Alvorada-TO, following the randomized complete block design with six treatments and four replications. Results show that the stem of A. peregrinum contains a significant amount of nitrogen, compared to other species, and high lignin content which makes it the most resistant species. The use of glycerin combined to the herbicide (picloram and triclopyr), was not efficient when compared to diesel oil. It was observed that the glycerin has potential as a vehicle for applying herbicides, leaving much to the development of new studies to make changes in its physicalchemical characteristics. Key words : Weeds, pastures, management, Adenocalymma peregrinum.

Electrolyte Effect on the Surface Roughness Obtained by Electropolishing of AISI 316L Stainless Steel

Electropolishing is a process for the surface finishing of metals and alloys, achieving brilliant surface finish with very low surface roughness values. The most common electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface finish of electropolished stainless steel. Each electrolyte had different concentrations of phosphoric acid, sulphuric acid, and chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, initial textures, and electrode positions. This study on the performance of three industrial electrolytes for the polishing of stainless steel AISI 316L revealed that adding chromic acid does not significantly enhance surface finish, and electropolishing ranges were quite similar for all three electrolytes.

Synthesis andin vitrodegradation of a novel magnesium oxychloride cement

Magnesium oxychloride cement (MOC) has been used in civil engineering as it exhibits a relatively high early strength and a low coefficient of thermal expansion. Its poor water resistance, although, has prevented its widespread use. Steady degradation when immersed in an aqueous environment, however, could be a beneficial property for a resorbable bone replacement. In this study, we have evaluated how different concentrations of phosphoric acid may be used to enhance water resistance providing some control over the rate of degradation. The phase compositions, microstructures, mechanical properties, and the degradation of MOC have been evaluated. As a preliminary assessment of biological suitability, the response of a population of bone marrow stromal cells to the surface was evaluated. X-ray diffraction data demonstrate that 5Mg(OH)₂ ·MgCl₂·8H₂O (phase 5) was formed in all MOC samples. The MOC modified with H₃PO₄ exhibits good water resistance and can sustain strength in aqueous medium and by adjusting H₃ PO₄ concentration; degradation speed may be controlled. Cells cultured on the surface of the MOC attached and retained viability over the duration of the study.

Electrochemical and structural characteristics of activated carbon-based electrodes modified via phosphoric acid

To improve the electrochemical performance of an activated carbon (AC)-based electric double-layer capacitor (EDLC), the AC surface, which is used as an electrode, was modified using different concentrations of phosphoric acid. The effects of the treatment on the surface and electrochemical properties of the AC electrodes were investigated. The specific capacitance increased from 256F/g for an untreated sample to 452F/g for a sample treated with a 2M solution at a scan rate of 5mV/s. This increase can be attributed to an increase in the mesopore volume caused by the etching effect of the reaction between the carbon surfaces and phosphoric acid. In addition, oxygen functional groups, which were introduced by the treatment, improved the electrochemical properties of the resulting AC-based electrode. Therefore, simultaneous etching and oxygen introduction with phosphoric acid can easily bind oxygen functional groups (particularly CO) onto the surface of an AC electrode. This method is effective at preparing AC for use in an EDLC with improved electrochemical properties.

Characterization of Surface Finish of Electropolished Stainless Steel AISI 316L with Varying Electrolyte Concentrations

Electropolishing is a process for the surface finishing of metals and alloys, achieving brilliant surface finish with very low surface roughness values. The most common electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface finish of electropolished stainless steel. Each electrolyte had different concentrations of phosphoric acid, sulphuric acid, and chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, initial textures, and electrode positions. This study on the performance of three industrial electrolytes for the polishing of stainless steel AISI 316L revealed that adding chromic acid does not significantly enhance surface finish, and electropolishing ranges were quite similar for all three electrolytes.

The Effect of Concentration of Phosphoric Acid on the Degree of Reduction of VPO Catalyst

Making VPO catalyst in the condition of different concentrations of Phosphoric acid and the temperatures，determine the average valence of vanadium. with the method of Potassium permanganate-Ferrous ammonium sulfate, to investigate the effect of different concentration of phosphoric acid on the average valence of catalyst, under the different temperatures. The structure, composition, crystal, and the Particle size has been characterized by XRD and SEM. The results confirmed that compare with higher concentration of phosphoric acid，the catalyst that were made with lower concentration phosphoric acid had the low average valence, greater specific surface area, better crystallinity, and more compact structure.

Influence of phosphoric acid treatment on hydrogen adsorption behaviors of activated carbons

The scope of this work investigates the relationship between the amount of oxygen-functional groups and hydrogen adsorption capacity with different concentrations of phosphoric acid. The amount of oxygen-functional groups of activated carbons (ACs) is characterized by X-ray photoelectron spectroscopy. The effects of chemical treatments on the pore structures of ACs are investigated by N2/77 K adsorption isotherms. The hydrogen adsorption capacity is measured by H2 isothermal adsorption at 298 K and 100 bar. In the results, the specific surface area and pore volume slightly decreased with the chemical treatments due to the pore collapsing behaviors, but the hydrogen storage capacity was increased by the oxygen-functional group characteristics of AC surfaces, resulting from enhanced electron acceptor-donor interaction at interfaces.