Impact of the oxygen functional group of nitric acid‑treated activated carbon on KOH activation reaction

Ji‑Hyun Kim,Sang Youp Hwang,Jung Eun Park,Gi Bbum Lee,Ho Kim,Seokhwi Kim,Bum Ui Hong 한국탄소학회 2019 Carbon Letters Vol.29 No.3

To prepare activated carbon with a high specific surface area, oxygen functional groups (OFGs) that can serve as useful electron donors during KOH activation were treated with nitric acid and incorporated into activated carbon. OFGs are incorporated differently according to the surface characteristics of starting materials. Up to 22.46% OFGs are incorporated into wood-based activated carbons (WACs), the C=O, COOH contents was 1.90, 17.05%, respectively. Whereas up to 12.82% OFGs are incorporated into coconut shell-based activated carbons, the C=O, COOH contents was 4.12, 6.15%, respectively. The OFGs used for increasing the specific surface area are the carbonyl group, and as the content of the functional group increases, the carbonyl group spreads to the carboxyl group. The specific surface area of activated carbons increased by 10–68% with an increase in the carbonyl group up to 6% (maximum point of carbonyl group). On the other hand, the specific surface area for WACs increased when the carboxyl group was 10% or below, but decreased by 6–15% when it increased to 10% or excess.

전기이중층 커패시터의 성능에 미치는 산소/질소 함유 관능기들의 영향

김지은 ( Ji Eun Kim ),권용갑 ( Young Kab Kwon ),이중기 ( Joong Kee Lee ),최호석 ( Ho Suk Choi ) 한국화학공학회 2012 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.50 No.6

본 논문에서는 전기이중층 커패시터(EDLC, Eclectical Double Layer Capacitor)의 전극소재로 쓰이는 활성탄소 의 안정화를 위해 산소함유관능기를 최소화하고 질소함유관능기의 도입을 통해 유기용액계의 전해질을 가지는 EDLC의 축전용량을 개선하는 연구를 하였다. 주사전자현미경(SEM, Scanning Electron Microscopy), 후리에 변환 적외선분광기(FTIR, Fourier Transform Infrared), 자동원소분석기(EA, Elemental Analysis), 보엠(Boehm) 적정법, 충·방전 테스트 등의 분석법을 이용하여 그 결과를 확인하였다. 산 처리를 통하여 산소함유관능기가 도입되고 요소 처리를 통하여 질소함유관능기가 도입되었음을 확인하였다. 질소함유관능기 도입을 통하여 EDLC의 g 당 방전용 량을 2mA 상승시켰으며 빠른 속도로 최대 충·방전 성능을 달성하였다. 반면 산소함유관능기는 전해질 속의 전하 가 탄소표면에 흡·탈착되는 것을 방해하기 때문에 낮은 방전용량을 보였고, 충·방전 횟수가 늘어남에 따라 방전용 량의 큰 감소를 보여주었다. In this study, activated carbons (ACs) were modified as electrode materials for an electric double layer capacitor (EDLC) by controlling oxygen- and nitrogen-containing functional groups. The morphological and chemical properties of ACs were analyzed through scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectrometer, automatic elemental analyzer (EA) and Boehm titration. Also, charge/discharge tests were performed to investigate the EDLC performance. Oxygen- and nitrogen-containing functional groups were introduced on the surface of ACs through acid and urea treatments, respectively. ACs with nitrogen-containing functional groups showed 2mA increase of gravimetric discharge capacity and quick achievement of maximum charge/discharge performance. However, ACs with oxygen-containing functional groups showed low discharge capacity and its gradual decrease during further cyclic test, since the functional groups interrupted adsorption/ desorption of charges in the electrolyte on the surface of ACs.

Correlations between electrochemical resistances and surface properties of acid-treated fuel in coal fuel cells

Eom, Seongyong,Ahn, Seongyool,Kang, Kijoong,Choi, Gyungmin Elsevier 2017 ENERGY Vol.140 No.1

<P><B>Abstract</B></P> <P>Herein, we investigate the relationship between fuel surface properties and inner resistances of direct carbon fuel cells (DCFCs) by subjecting raw coal to a liquid-phase chemical treatment and correlating its surface property changes (e.g., degree of oxidation, surface area, and ash composition) with those of electrochemical resistances. Fuel surface characteristics are analyzed by thermogravimetry, gas adsorption, and X-ray photoelectron spectroscopy, with correlations established using the Pearson correlation analysis. The obtained results show that the surface Si content is strongly correlated with electrolyte resistance due to influencing the concentration of carbonate ions. Moreover, charge transfer resistance is strongly negatively correlated with the surface oxygen content, since oxygenated functional groups (e.g., carbonyl and quinone moieties) enhance the oxidation of solid carbon by increasing its reactivity and wettability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of surface properties on resistances are investigated in carbon fuel cell. </LI> <LI> The performance and resistance of raw coal and treated coals are compared. </LI> <LI> Si content on the fuel surface has a correlation with the electrolyte resistance. </LI> <LI> The charge transfer resistance is affected by surface oxygen groups. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Non-uniformly functionalized titanium carbide-based MXenes as an anchoring material for Li-S batteries: A first-principles calculation

Sim, Eun Seob,Chung, Yong-Chae Elsevier BV * North-Holland 2018 Applied Surface Science Vol.435 No.-

<P><B>Abstract</B></P> <P>In this study, the influence of the non-uniform surface of F- and O-functionalized Ti<SUB>2</SUB>C on the anchoring behavior of lithium polysulfide (LiPS) is investigated using density functional theory. In order to consider the non-uniform surface, the substitutional, vacancy, and S-trapped sites of F- and O-functionalized Ti<SUB>2</SUB>C are designed. The anchoring behavior is investigated considering the adsorption energy of LiPS, reactivity between Li atoms and the substrate, and the reduction state of the S atoms. On the F-substitutional site of the O-functionalized surface, it is confirmed that the suppressing mechanism changes from the neutralization of S atoms to the anchoring of LiPS. However, too strong of an interaction between Ti atoms exposed at the vacancy site and S atoms induces trapping of the S atom at the vacancies of both F- and O-functionalized surfaces. As a result of the trapping of the S atom, the use of active material decreases. In addition, the S-trapped site originated from the vacancy site does not affect the suppressing mechanism. In conclusion, to optimize the Ti<SUB>2</SUB>C-based MXene as an anchoring material for Li-S batteries, the preparation process should be focused on eliminating the vacancy of functional groups.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Substitutional, vacancy, S-trapped sites are designed to consider non-uniform Ti<SUB>2</SUB>C. </LI> <LI> Neutralization of S does not occur on F-substitutional site of O-functionalized Ti<SUB>2</SUB>C. </LI> <LI> S atoms are trapped on vacancy site of both F- and O-functionalized Ti<SUB>2</SUB>C. </LI> <LI> Suppressing mechanism is not affected by S-trapped site. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Impact of the oxygen functional group of nitric acid-treated activated carbon on KOH activation reaction

김지현,황상엽,박정은,이기범,김호,김석휘,홍범의 한국탄소학회 2019 Carbon Letters Vol.29 No.3

To prepare activated carbon with a high specific surface area, oxygen functional groups (OFGs) that can serve as useful electron donors during KOH activation were treated with nitric acid and incorporated into activated carbon. OFGs are incorporated differently according to the surface characteristics of starting materials. Up to 22.46% OFGs are incorporated into wood-based activated carbons (WACs), the C=O, COOH contents was 1.90, 17.05%, respectively. Whereas up to 12.82% OFGs are incorporated into coconut shell-based activated carbons, the C=O, COOH contents was 4.12, 6.15%, respectively. The OFGs used for increasing the specific surface area are the carbonyl group, and as the content of the functional group increases, the carbonyl group spreads to the carboxyl group. The specific surface area of activated carbons increased by 10–68% with an increase in the carbonyl group up to 6% (maximum point of carbonyl group). On the other hand, the specific surface area for WACs increased when the carboxyl group was 10% or below, but decreased by 6–15% when it increased to 10% or excess.

Adsorption Behaviors of Noxious Gases on Chemically Surface-treated Activated Carbons

Park, Soo-Jin,Shin, Jun-Sik 한국탄소학회 2003 Carbon Letters Vol.4 No.1

The specific adsorption behaviors of activated carbons (ACs) treated with 30 wt% $H_3PO_4$ or NaOH were investigated in the removals of NO or $NH_3$. The acid and base values were determined by Boehm's titration method. And, the surface properties of ACs were studied by FT-IR and XPS analyses. Also, $N_2/77K$ adsorption isotherm characteristics, including the specific surface area and micropore volume were studied by BET and t-plot methods, respectively. From the adsorption tests of NO and $NH_3$, it was revealed in the case of acidic treatment on ACs that the $NH_3$ removal was more effective due to the increase of acidic functional groups in carbon surfaces. Also, the NO removal was increased, in the case of basic treatment, due to the improvement of basic functional groups, in spite of significant decreases of BET's specific surface area and total pore volume. It was found that the adsorption capacity of ACs was not only determined by the textural characteristics but also correlated with the surface functional groups in the acid-base intermolecular interactions.

Surface modification and adsorption of eucalyptus wood-based activated carbons: Effects of oxidation treatment, carbon porous structure and activation method

Chaiyot Tangsathitkulchai,Yuvarat Ngernyen,Malee Tangsathitkulchai 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.5

The incorporation of oxygen functional groups onto the surface of eucalyptus activated carbon and its surface chemistry were investigated as a function of oxidation conditions, carbon porous properties and carbon preparation method. Under all treatment conditions of increasing time, temperature and oxidant concentration, liquid oxidation with HNO3, H2O2 and (NH4)2S2O8 and air oxidation led to the increase of acidic group concentration, with carboxylic acid showing the largest percentage increase and air oxidation at the maximum allowable temperature of 350℃ produced the maximum content of both carboxylic acid and total acidic group. Nitric acid oxidation of chemically activated carbon produced higher total acidic content but a lower amount of carboxylic acid compared to the oxidized carbon from physical activation. The increased contents of acidic groups on oxidized carbons greatly enhanced the adsorption capacity of water vapor and heavy metal ions.

Enhancement of surface stability of lithium manganese oxide spinel by silyl-group functionalized fluoride-responsive ionic liquid additives

Seo, Hyoree,Na, Subin,Lee, Boeun,Yim, Taeeun,Oh, Si Hyoung Elsevier 2018 Journal of industrial and engineering chemistry Vol.64 No.-

<P><B>Abstract</B></P> <P>Spinel-structured lithium manganese oxides are considered as promising cathode material, however, their widespread commercial application remains hampered by their poor surface instability. To overcome these problems, we designed and synthesized task-specific ionic liquid additives that can effectively scavenge trace amounts of fluoride in the cell. Addition of ionic liquid additives in the electrolyte significantly improves cycling retention. <SUP>1</SUP>H- and <SUP>19</SUP>F-nuclear magnetic resonance spectroscopy measurements and inductively coupled plasma mass spectrometry elemental analysis collaboratively provides clear evidence that the ionic liquid additives selectively suppress parasitic reactions of the electrolyte with the surface of lithium manganese oxides cathode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Surface instability of LMO spinel is improved by IL additives with silyl-functional group. </LI> <LI> Silyl-group functionalized fluoride-responsive ILs are synthesized and characterized. </LI> <LI> IL with silyl functional group can effectively eliminate nucleophilic fluorides. </LI> <LI> Chemical reactivity of IL with F<SUP>−</SUP> is confirmed by NMR analysis. </LI> <LI> LMO spinel with IL additives exhibits excellent electrochemical performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

습식 표면개질 처리된 폴리이미드 필름 표면의 특성에 관한 연구

구석본(S.B. Koo),이홍기(H.K. Lee) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.4

Metallized Polyimide films are extensively used as base materials in microelectronics, optical and automotive applications. However it is difficult to deposit metals on those because of their structural stabilities. In this work, polyimide films are modified by a wet process with alkalinemetalhydroxide and additives to introduce functional groups. The surface molecular structures of polyimide are investigated using X-ray photoelectron spectroscopy(XPS), fourier transform infrared reflection spectroscopy(FTIR-ATR), atomic force microscopic(AFM). XPS spectra and FTIR spectra show that the surface structure of polyimide is converted into potassium polyamate. AFM image and AFM cross-sectional analyses reveal the increased roughness on the modified surface of polyimide films. As a result, it is shown that the adhesion strength between polyimide surface and electroless nickel layer is increased by the nano-anchoring effect.

Selective Removal of Cr (VI) and Cr (III) in Aqueous Solution by Surface Modified Activated Carbon

Lee, Jeong-Min,Kim, Min-Il,Lee, Young-Seak Korean Carbon Society 2008 Carbon Letters Vol.9 No.1

The adsorption and reduction of Cr (VI) to Cr (III) by surface modified activated carbon (AC) in an aqueous solution was studied. The effects of surface modifications on the properties of the carbons were investigated by the analysis of specific surface area, carbon surface pH, acid/base surface values and functional groups. In order to understand the Cr(VI) adsorption and reduction ratio from Cr(VI) to Cr(III), the Cr adsorption capacity of AC was also measured and discussed by using inductively coupled plasma and UV spectrophotometer. The modifications bring about substantial variation in the chemical properties whereas the physical properties such as specific surface area, pore volume and pore size distribution nearly were not changed. Total Cr adsorption efficiency of as-received activated carbon (R-AC) and nitric acid treated activated carbon (N1-AC and N2-AC) were recorded on 98.2, 99.7 and 100%. Cr(III) reduction efficiency of R-AC increased largely from 0.4% to 28.3% compared to N1-AC and N2-AC.