New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical ...entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL(-1), they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/GOx/PEI/CNT) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/GOx/PEI/CNT, including 4 mg mL(-1) GOx displays a high electron transfer rate, followed by excellent catalytic activity and EBC performance.
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•Heat treated PdxFey/Cs are prepared for the anodic catalyst of DFAFC.•The formation of Pd–Fe structure is confirmed by XANES spectra.•IFAOR way is activated through heat ...treatment.•Heat treated Pd3Fe1/C shows the best catalytic activity.•The MPD of heat treated Pd3Fe1/C is 1.9 times higher than that of Pd/C.
The palladium–iron based bimetallic catalysts (PdxFey/Cs) and facile synthetic method are introduced to enhance the catalytic activity and operational duration for direct formic acid fuel cells. To improve the properties of PdxFey/C catalysts, such as degree of PdFe alloy and its crystallinity, heat treatment is conducted at 600°C. According to results, the Pd–Fe bond and Fe metal particle are formed after the heat treatment, while iron oxides and Pd particles are observed in the untreated samples. Electrochemical evaluations for measuring the formic acid oxidation reaction rate demonstrates heat treated Pd3Fe1/C (HT-Pd3Fe1/C) is the best catalysts of six samples which are synthesized by using different Pd to Fe ratios (3:1, 1:1, 1:3) before and after heat treatment. This is because the HT-Pd3Fe1/C has high Pd–Fe alloying and Pd contents. Through the heat treatment, the indirect formic acid oxidation reaction way is activated and the resistance to CO poisoning is significantly improved. The maximum power density of direct formic acid fuel cells using HT-Pd3Fe1/C whose open circuit voltage is 0.83V is 137mWcm−2, which is 1.6 and 1.9 times higher than that of direct formic acid fuel cells using untreated catalyst and Pd/C.
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•A new cascade type CNT/PEI/IPA-Hemin/GOx catalyst is introduced.•Onset potential for HRR is positively shifted due to adoption of axial ligands.•Axial ligand forms the coordination ...bonds with Fe core ions within hemin.•MPD of membraneless EBC using a new cathodic catalyst is 66.0 μWcm−2.•CNT/PEI/IPA-Hemin/GOx plays its role well as cathodic catalyst.
A new cascade type cathodic catalyst containing hemin and glucose oxidase (GOx) is suggested for enhancing the performances of enzymatic biofuel cells (EBCs). In the cathodic catalyst, the upper GOx layer generates hydrogen peroxide (H2O2) by glucose oxidation reaction (GOR), and then actual cathodic current is determined by H2O2 reduction reaction (HRR) catalyzed by hemin, using the pre-produced H2O2. The reaction potential of hemin is positively shifted by the formation of coordinate bond between its core ions and amine groups, meaning that that of HRR deciding reduction onset potential of the catalyst is positively shifted. As materials providing the ligand containing amine groups, polyethyleneimine (PEI) and imidazole propionic acid (IPA) are considered. According to evaluations, the reaction potential for HRR is favorably moved as the amounts of available ligand and coordinate bond increase. When IPA is applied, the reduction onset potential for HRR is shifted from 0.4 to 0.51V and reduction reaction rate also increases from 55 to 86 μAcm−2. Based on that, the EBC using catalyst containing IPA shows superior performances, such as maximum power density of 66 μWcm−2 and open circuit voltage of 0.65V.
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•CNT/PEI/GNP-NPT/LAC catalyst is suggested as cathodic catalyst for EBC.•Onset potential and ORR are improved by the adoption of PEI and GNP-NPT.•PEI induces more immobilization of ...laccase molecules.•GNP-NPT acts as electron relay between T1 of laccase and supporter.•EBC using CNT/PEI/GNP-NPT/LAC shows the best performance.
New catalyst for promoting oxygen reduction reaction (ORR) and enzymatic biofuel cell (EBC) performance is suggested. The catalyst consist of laccase (LAC) and gold nanoparticle (GNP)-naphthalenethiol (NPT), which are linked to polyethyleneimine (PEI) and carbon nanotube (CNT) (CNT/PEI/GNP-NPT/LAC). Its onset potential and ORR rate are improved due to adoptions of PEI and GNP-NPT. Namely, CNT/PEI induces more immobilization of LACs and GNP-NPT acts as electron relay between CNP and NPT by thiol-gold bond and between CNT/PEI and LACs by electron collection effect. Even in EBC measurement, maximum power density of EBC using CNT/PEI/GNP-NPT/LAC is highest as 13μWcm−2.
Carbon supported palladium-copper (Pd-Cu) bimetallic catalysts (Pd
x
Cu
y
/Cs) are fabricated by modified polyol method to enhance the reaction rate of formic acid oxidation reaction (FAOR) and the ...performance of direct formic acid fuel cell (DFAFC) through weakening the bond with the intermediate of formic acid. According to the evaluations, when the ratio of Pd and Cu is 3 : 1 (Pd
3
Cu
1
/C), catalytic activity is best. Its maximum current density is 1.68-times better than that of commercial Pd/C. Even from the optical and spectroscopic characterizations, such as TEM, EDS, XPS and XRD, Pd
3
Cu
1
/C shows an optimal particle size and a higher degree of alloying. This is because in Pd
3
Cu
1
/C catalyst, the d-band center that induces the weakening in adsorption of formate anion groups to Pd surface is most positively shifted, and this positive shift promotes the reaction rate of FAOR, which is the rate determining step. When the performance of DFAFCs using the Pd
x
Cu
y
/C catalysts is measured, the maximum power density (MPD) of DFAFC using Pd
3
Cu
1
/C catalyst is 158 mW cm
−2
, and this is the best MPD compared to that of DFAFCs using other Pd
x
Cu
y
/C catalysts. In addition, in a comparison with commercial Pd/C catalyst, when the same amount of catalyst is loaded, MPD of DFAFC using Pd
3
Cu
1
/C catalyst is 22.5% higher than that of DFAFC using commercial Pd/C.
본 논문에서는 hemin, 폴리에틸렌이민(PEI) 및 탄소나노튜브(CNT)를 이용하여 제조 CNT/PEI/hemin/PEI 복합재에 가교제인 테레프탈알데하이드(TPA)를 첨가하여 전자전달이 개선된 과산화수소 환원 반응(HPRR) 촉매를 합성하였다. 합성된 촉매(CNT/PEI/hemin/PEI/TPA)를 과산화수소 10 mM 농도에서 HPRR 반응성을 ...확인한 결과, 0.2 V (vs. Ag/AgCl)에서 0.2813 mA cm -2 의 전류 밀도로 나타났으며, 이는 가교하지 않은 촉매(CNT/PEI/hemin/PEI)와 범용 가교제인 글루타르알데하이드(GA)에 의해 가교된 촉매(CNT/PEI/hemin/PEI/GA)에 비해 각각 2.43 및 1.87배 증가하였다. CNT/PEI/hemin/PEI/TPA의 HPRR 개시전위는 0.544 V로서 CNT/PEI/hemin/PEI와 CNT/PEI/hemin/PEI/GA의 0.511 및 0.471 V에 비하여 원활한 전자전달에 의해 개선되었음을 확인할 수 있었다. 이는 전기화학 임피던스 분광법(EIS)을 이용한 분석 결과에서도 확인되었는데, CNT/PEI/hemin/PEI/GA의 경우, 전자전달을 방해하는 가교제의 도입에 따라 CNT/PEI/hemin/PEI에 비하여 높은 전자전달저항을 나타낸 반면, CNT/PEI/hemin/PEI/TPA는 6.2% 감소하여, 가장 낮은 전자전달저항을 나타냈다. 막이 없는 흐름형 과산화수소 연료전지를 이용한 평가에서도, CNT/PEI/hemin/PEI/TPA를 환원극으로 활용한 전지의 최대 출력 밀도가 36.34±1.41 μWcm -2 로, CNT/PEI/hemin/PEI (27.87±0.95 μWcm -2 )와 CNT/PEI/hemin/PEI/GA(25.57±1.32 μWcm -2 ) 보다 높게 측정되어, TPA는 전자전달을 개선 성능을 확인할 수 있었다.
Terephthalaldehyde (TPA) is introduced as a cross liker to enhance electron transfer of hemin-based cathodic catalyst consisting of polyethyleneimine (PEI), carbon nanotube (CNT) for hydrogen peroxide reduction reaction (HPRR). In the cyclic voltammetry (CV) test with 10 mM H 2 O 2 in phosphate buffer solution (pH 7.4), the current density for HPRR of the suggested catalyst (CNT/PEI/hemin/PEI/TPA) shows 0.2813 mA cm -2 (at 0.2 V vs. Ag/ AgCl), which is 2.43 and 1.87 times of non-cross-linked (CNT/PEI/hemin/PEI) and conventional cross liker (glutaraldehyde, GA) used catalyst (CNT/PEI/hemin/PEI/GA), respectively. In the case of onset potential for HPRR, that of CNT/PEI/hemin/PEI/TPA is observed at 0.544 V, while those of CNT/PEI/hemin/PEI and CNT/PEI/hemin/PEI/GA are 0.511 and 0.471 V, respectively. These results indicate that TPA plays a role in facilitating electron transfer between the electrodes and substrates due to the π-conjugated cross-linking bonds, whereas conventional GA cross-linker increases the overpotential by interrupting electron and mass transfer. Electrochemical impedance spectroscopy (EIS) results also display the same tendency. The charge transfer resistance (Rct) of CNT/PEI/hemin/PEI/TPA decreases about 6.2% from that of CNT/PEI/hemin/PEI, while CNT/PEI/hemin/PEI/GA shows the highest Rct. The polarization curve using each catalyst also supports the superiority of TPA cross liker. The maximum power density of CNT/PEI/hemin/ PEI/TPA (36.34±1.41 μWcm -2 ) is significantly higher than those of CNT/PEI/hemin/PEI (27.87±0.95 μWcm -2 ) and CNT/PEI/hemin/PEI/GA (25.57±1.32 μWcm -2 ), demonstrating again that the cathode using TPA has the best performance in HPRR.
전 세계에서 수소자동차 충전의 기초로 사용되는 SAE J2601의 내용과 충전 프로토콜의 목적과 개념을 조사하고, 우리나라의 프로토콜 관련 연구 내용을 조사하였다. 그리고, 우리나라에서 개발한 수소 충전 성능평가 장비의 구성 요소와 수소충전소의 성능과 안전을 평가할 수 있는 방법에 대해 검토하고, 현재 국내에서 운영하고 있는 수소충전소에 대해 현장 적용을 ...실시하였다. 또한, 국내에서 운영 중인 수소충전소에서 수집한 데이터를 이용하여 경제성 분석을 하였다. 수소충전소의 안전성과 경제성을 확보하기 위해서는 프로토콜을 만족하여야 하며, 프로토콜을 만족하기 위해서는 충전온도, 충전압력, 충전 유량이 안전한 범위 내에서 제어되고 있는지 평가하는 것이 필요하다.
The purpose of the refueling protocol and the contents of SAE J2601, which is used as the basis for hydrogen vehicles refueling around the world, were investigated, and research contents related to domestic protocols were also investigated. In addition, the components of the hydrogen refueling performance evaluation device developed in Korea and the method for evaluating the performance and safety of hydrogen refueling stations were reviewed. And, the result were analyzed by applying it to the hydrogen refueling stations currently operating in Korea. In addition, an economic feasibility analysis was conducted using data collected from domestic hydrogen refueling stations. In order to secure the safety and economy of a hydrogen refueling station, the protocol must be satisfied, and in order to satisfy the protocol, it is necessary to evaluate whether the refueling temperature, refueling pressure, and refueling flow are controlled within a safe range.
A borate-group functionalized carbon nanotube (Borate-CNT) catalyst is developed to enhance the performance and long term durability of the vanadium redox flow battery (VRFB). To prepare for the ...–Borate-CNT catalyst, carboxylic acid groups (COOHs) adopted onto acidified CNT (CA-CNT) are simply co-treated with sodium hydroxide (NaOH) and boric acid (H3BO3). As a result, the COOHs are transformed into borate groups. The transformation is verified by XPS analysis, showing the increase in oxygen content and the creation of boron-oxygen bonds. The active sites and catalytic activity of Borate-CNT are increased more than those of the catalysts formed by the single treatment of NaOH and CA-NCT or H3BO3 and CA-CNT. This is due to the increase of active sites by the formation of oxygen abundant borate groups and the different electronegativity between the boron and oxygen elements promotes the attraction and subsequent reaction o f vanadium ions. The voltage and energy efficiencies (VE and EE) of the VRFB using Borate-CNT catalyst are better than those of VRFBs using no catalyst or CA-CNT catalyst – even at 200 mA cm−2 – and the efficiencies of Borate-CNT VRFB are well maintained until 300 cycles, whereas the efficiencies of the no catalyst VRFB are considerably decreased (17% and 16% decreases of the initial values in VE and EE). In addition, Borate-CNT shows the effect of protection by suppressing the chemical aging of carbon felt from toxic acidic electrolyte.
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•Borate-CNT is suggested as a catalyst for both side of VRFB.•The performance and long term durability of VRFB is enhanced by Borate-CNT.•Co-treatment by NaOH and boric acid increase the active site on the surface of CNT.•Boron-oxygen bonds promote the redox reaction of vanadium ions.•VE and EE are improved considerably by adoption of Borate-CNT on carbon felt.
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•Co(TiPA) and Fe(TiPA) are suggested as redox couple of RFB.•TiPA complexes have high stabilization constant.•TiPA complexes has better long cycle stability than TEA complexes.•Energy ...efficiency and power density of RFB using Co(TiPA) and Fe(TiPA) are high.•RFB using Co(TiPA) and Fe(TiPA) shows excellent capacity retention for 298 h.
Two metal-organic complexes consisting of new triisopropanolamine (TiPA) ligand and two transition cobalt (Co) and iron (Fe) metals (Co(TiPA) and Fe(TiPA)) are suggested and used as redox couple for redox flow battery (RFB) with potassium hydroxide (KOH) electrolyte. The redox reactivity of Co(TiPA) and Fe(TiPA) adopting TiPA ligand is measured and their reaction mechanism is compared with that of complexes containing triethanolamine (TEA) ligand (Co(TEA) and Fe(TEA)) that are conventionally considered. According to evaluations, the reaction rate of all complexes is controlled by their diffusion rate. In a comparison of the complexes, that of TEA complexes is faster than that of TiPA complexes. This means that the viscosity of TEA complexes is lower than that of TiPA complexes. However, regarding the stability in KOH, the stability of TiPA complexes is much better than that of TEA complexes, enabling the stable redox reactions over a long period. Considering the reduction potential of complexes and their stabilization constant, TiPA complexes have a higher stabilization constant than TEA complexes because the redox reaction of TiPA complexes is stably performed, whereas the Fe ions of Fe(TEA) are precipitated for charging process and the preciptation induces irreversible reaction in KOH. This is confirmed by the solidified Fe atoms observed onto carbon felt after RFB test. When the performance of RFB using Co(TiPA) and Fe(TiPA) is measured, its capacity retention is well maintained for 100 cycle (298 h), while this RFB shows superior energy efficiency (77% at 40 mA cm−2) and power density (81.3 mW cm−2 at 160 mA cm−2).
Organometallic complexes consisting of iron- and cobalt-triethanolamine ligand (Fe (TEA) and Co(TEA)) are proposed as redox couple of aqueous redox flow battery (ARFB). Fe (TEA) and Co(TEA) are ...dissolved in sodium hydroxide (NaOH) electrolyte, while their chemical stability and electrochemical reactivity are quantitatively characterized. As a result, the chemical stability of Co(TEA) is degraded for multiple charge/discharge cycle test due to the deformation of unchelated TEAs by the chemical reaction with hydroxyl ion (OH−) and the catalytic effect of Co(TEA). To address the issue, the ratio of Co to TEA and the concentration of NaOH are manipulated. When the ratio is 1:1, the redox reactivity of Co(TEA) is improved because the amount of unchelated TEAs that is a reason for lowering its redox reactivity is minimized, while 4 M NaOH is proper to supply enough amount of OH−, preserving its chemical structure and reducing mass transfer retardation. Regarding Fe (TEA), with 1:2.5 ratio of Fe to TEA in 4 M NaOH, the stability and performance of Fe (TEA) are best. Performance of ARFB using 1:2.5 Fe (TEA) and 1:1 Co(TEA) shows excellent results of high charge and energy efficiencies of 99% and 62% at 40 mA cm−2, and high power density of 35 mWcm−2.
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•Fe (TEA) and Co(TEA) are proposed as redox couple of ARFB.•Optimal ratio of Co ion and TEA ligand is determined for optimal Co(TEA).•4 M NaOH is required for optimizing 1:2.5 Fe (TEA) and 1:1 Co(TEA).•ARFB using this redox couple shows excellent CE (99%) and power density (35 mW cm−2).•Electrolyte cost per capacity of ARFB is 43% lower than VRFB.
