With the continuing advances in technology, electrical energy storage has become increasingly important. Among storage devices supercapacitors’ distinct qualities, such as a long lifespan, quick charge/discharge speeds, and high-power density, make them viable substitutes for traditional batteries. In this study a simple hydrothermal method was used to synthesize a h-MoO3/graphene oxide (GO) composite for such applications. The crystal structure, morphology, and chemical bonding were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and Raman spectroscopy. XRD confirmed the hexagonal crystal structure, and no changes were observed after GO incorporation. The FESEM images revealed that the nanosheets of GO and hexagonal rods MoO3 were well coupled with the GO sheets. The electrochemical properties of the pure h-MoO3 and h-MoO3/GO composites were studied using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The nanocomposite electrode demonstrated a specific capacitance of 134 Fg-1 at a current density of 3 mA/cm-2, an energy density of 26.8 Wh/kg-1, and power density of 560 W/kg-1 in an aqueous acidic electrolyte 1 M H2SO4, which is notably higher than that of pure MoO3. This indicates the promising electrochemical performance of MoO3/GO composite for supercapacitor applications. The enhanced capacitive performance may have resulted from the decrease in the charge transfer resistance (Rct), calculated from the Nyquist plot. Furthermore, the composite material exhibited stability and a capacitive retention of 76 % after 1,000 cycles. This confirms the benefits of incorporating GO to enhance material retention for better long-term results. The results of this study demonstrate its potential to advance energy storage technology. Maintaining the hexagonal crystal structure of h-MoO3 while incorporating GO improves the composite’s structural stability, an important factor for reliable long-term use. Moreover, the observed reduction in crystallite size due to the presence of GO suggests improved electrochemical performance.

Among the products of the electrocatalytic reduction of carbon dioxide (CO2RR), CO is currently the most valuable product for industrial applications. However, poor stability is a significant obstacle to CO2RR. Therefore, we synthesized a series of bimetallic organic framework materials containing different ratios of tungsten to copper using a hydrothermal method and used them as precursors. The precursors were then subjected to pyrolysis at 800 °C under argon gas, and the M-N bimetallic sites were formed after 2 h. Loose porous structures favorable for electrocatalytic reactions were finally obtained. The material could operate at lower reduction potentials than existing catalysts and obtained higher Faraday efficiencies than comparable catalysts. Of these, the current density of WCu-C/N (W:Cu = 3:1) could be stabilized at 7.9 mA ‧ cm-2 and the FE of CO reached 94 % at a hydrogen electrode potential of -0.6 V (V vs. RHE). The novel materials made with a two-step process helped to improve the stability and selectivity of the electrocatalytic reduction of CO2 to CO, which will help to promote the commercial application of this technology.

Achieving cost-effective and defect-free graphene sheets is highly desirable for sensor devices. Aiming this, few-layer graphene (~ 3) sheets are prepared by an electrochemical exfoliation with [NMP] [ HSO4] electrolyte (i.e., Bronsted acidic ionic liquid). A novel approach for the effective exfoliation of graphene sheets is demonstrated by (i) simultaneously applying a constant potential through an electrochemical cell (with different electrolyte concentrations) and (ii) together with sonication. The exfoliated graphene sheets are characterized through state-of-the-art techniques and sprayed on a glass substrate at optimum conditions. Thus, the transparent conducting sensor device is fabricated with a suitable contact electrode and used for ammonia vapor sensing and the sensor performances are highly dependent on the concentration of the ionic liquid used during the electrochemical exfoliation. The sensing response and limit of detection for the exfoliated graphene-based film were calculated as 3.56% and 432 ppb, respectively. Further studies indicated that the fabricated sensors are more selective towards ammonia molecules with quick response and recovery times.

A simple and one-pot synthetic procedure using two different sources has been demonstrated to prepare heteroatoms doped reduced graphene oxide such as nitrogen-doped reduced graphene oxide (N-RGO) and sulfur-doped reduced graphene oxide (S-RGO). The N-RGO has been hydrothermally synthesized using urea as nitrogen precursor, wherein the S-RGO has been synthesized using dimethyl sulfoxide (DMSO) as sulfur precursor. The successful N-doping, S-doping and other physicochemical properties of N-RGO and S-RGO have been confirmed with different spectroscopic and electrochemical techniques. The results indicated that doping into the graphene structure exhibits a high conductivity and a better transfer of charge. Moreover, heteroatoms doped graphene (N-RGO and S-RGO) and graphene-related materials (RGO) have been applied for the individual detection of uric acid (UA). Interestingly, the N-RGO exhibited a lower limit of detection (LOD, S/N = 3) of 2.7 10– 5 M for UA (10–1000 μM) compared with undoped RGO and S-RGO. Furthermore, the simultaneous detection of UA in the presence of Xanthine (XA) has been demonstrated a wide linear range of detection for UA: 10–1000 μM, with unchanged concentration of XA to be 200 μM, and exhibited a low limit of detection of 8.7 10− 5 M ( S∕N = 3) for UA. This modified sensor based on N-RGO has revealed a high selectivity and reproducibility thanks to its large surface area, high catalytic properties, and chemical structure. Indeed, the practical applicability of the proposed sensor has been evaluated in milk samples even in the presence of high concentrations of UA with satisfactory results.

Recently, hollow carbon spheres (HCS) have aroused great interests in the field of energy storage and conversion owing to their unique morphology, structure and other charming properties. Nevertheless, unsatisfactory electrical conductivity and relatively poor volumetric energy density caused by inevitable gaps between discrete carbon spheres greatly impede the practical application of HCS. In this work, for the first time we propose a novel dual-template strategy and successfully fabricate interconnected 3D hollow N-doped carbon network (HNCN) by a facile and scalable pyrolysis process. By systematical characterization and analysis, it can be found that HNCN is assembled by HCS and lots of mesoporous carbon. Compared to the counterparts, the obtained HNCN exhibits unique 3D interconnected architecture, larger specific surface area, hierarchical meso/macropore structure, higher structure defects, higher N doping amount and more optimized N configurations (especially for pyridinic-N and graphitic-N). As a result, these advantageous features endow HNCN with remarkably promoted electrochemical performance for supercapacitor and oxygen reduction reaction. Clearly, our proposed dual-template strategy provides a good guidance on overcoming the intrinsic shortcomings of HCS, which undoubtedly broadens their application in energy storage and conversion.

This work describes the facile synthesis of silver nanoparticle-decorated zinc oxide nanocomposite through a simple glycol reduction method. The silver nanoparticle-decorated zinc oxide nanocomposite-based pencil graphite electrode has been validated as a perceptive electrochemical sensing podium towards nitrite. The morphology of the prepared nanocomposite has been characterized via specific spectroscopic and electrochemical techniques. The sensor exhibits a notable enhancement in the cyclic voltammetric response to nitrite oxidation at an ideal peak potential of 0.76 V in pH 6.0 acetate buffer. Under optimum conditions of nitrite directly expanded with their concentration in the range from 30 to 1400 μM with a detection limit of 14 μM.

The composites of carbon nanotube (CNT) supported by Sn-doped MnO2 with enhanced capacitance have been fabricated with varying dopant concentrations. The composites have been subjected to physiochemical, configurational, and morphological analyses by FTIR, UV–Vis spectroscopy, X-ray diffraction and field emission scanning electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction studies. The electrochemical performance of the composite has been evaluated by cyclic voltammetry and charge/discharge techniques. Highest specific capacitances of 940 F g−1 at a current density of 0.35 A g−1 and 927 F g−1 at 5 mV s−1 in 1 M Na2SO4 electrolyte solution was achieved in the case of 5% Sn doped composite. Moreover, the electrode demonstrated good cycling performance and retaining 79.7% of the initial capacitance over 3000 cycles. The superior electrochemical performance is accredited mainly to the porous sheath hierarchical architecture, which consist of inter connected MnO2 nanoneedles uniformly coated over the CNT surface. This peculiar architecture is responsible for fast ion/electron transfer and easy access of the active material.

In anion exchange membrane fuel cells, Pd nanoparticles are extensively studied as promising non-Pt catalysts due to their electronic structure similar to Pt. In this study, to fabricate Pd nanoparticles well dispersed on carbon support materials, we propose a synthetic strategy using mixed organic ligands with different chemical structures and functions. Simultaneously to control the Pd particle size and dispersion, a ligand mixture composed of oleylamine(OA) and trioctylphosphine(TOP) is utilized during thermal decomposition of Pd precursors. In the ligand mixture, OA serves mainly as a reducing agent rather than a stabilizer since TOP, which has a bulky structure, more strongly interacts with the Pd metal surface as a stabilizer compared to OA. The specific roles of OA and TOP in the Pd nanoparticle synthesis are studied according to the mixture composition, and the oxygen reduction reaction(ORR) activity and durability of highly-dispersed Pd nanocatalysts with different particles sizes are investigated. The results of this study confirm that the Pd nanocatalyst with large particles has high durability compared to the nanocatalyst with small Pd nanoparticles during the accelerated degradation tests although they initially indicated similar ORR performance.

Using a high pressure homonizer, we report on the electrochemical performance of Li4Ti5O12(LTO) particles manufactured as anode active material for lithium ion battery. High-pressure synthesis processing is performed under conditions in which the mole fraction of Li/Ti is 0.9, the synthesis pressure is 2,000 bar and the numbers of passings-through are 5, 7 and 10. The observed X-ray diffraction patterns show that pure LTO is manufactured when the number of passings-through is 10. It is found from scanning electron microscopy analysis that the average size of synthesized particles decreases as the number of passings-through increases. LiCoO2-based active cathode materials are used to fabricate several coin half/full cells and their battery characteristics such as lifetime, rate capability and charge transfer resistance are then estimated, revealing quite good electrochemical performance of the LTO particles as an effective anode active material for lithium secondary batteries.

Electrochemical synthesis was employed to prepare a novel hydroxyapatite/graphene (HAP/ Gr) composite powder suitable for medical applications as a hard tissue implant (scaffold). The synthesis was performed in a homogeneous dispersion containing Na2H2EDTA·2H2O, NaH2PO4 and CaCl2 with a Ca/EDTA/PO4 3− concentration ratio of 0.25/0.25/0.15M, along with 0.01 wt% added graphene nanosheets, at a current density of 137 mA cm−2 and pH value of 9.0. The field emission scanning electron microscopy and transmission electron microscopy observations of the composite HAP/Gr powder indicated that nanosized hydroxyapatite particles were uniformly placed in the graphene overlay. Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction confirmed graphene incorporation in the HAP/Gr powder. The electrochemically prepared HAP/Gr composite powder exhibited slight antibacterial effect against the growth of the bacterial strain Staphylococcus aureus.

Carbazole과 diketopyrrolopyrrole를 기본 골격으로 한 2,5-bis-(2-butyl-octyl)-3,6-bis-[5-(4-carbazol-9-ylphenyl)-thiophen-2-yl] -2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione (PCTDPP12)을 스즈키 커플링 반응을 이용하여 합성하였다. UV-Visible 분광법으로 확인 한 결과 PCTDPP의 용액과 필름의 최대 흡수 피크는 각각 643 nm와 671 nm이며, PCTDPP12의 광학적 밴드갭은 각각 1.84 eV이다. 열처리에 의해 PCTDPP12의 UV-visible 흡광도 및 최대 흡수 파장이 변화된는 것을 관찰 하였다. 그리고 순환 전압 전류법에 의해 조사한 PCTDPP12의 HOMO 및 LUMO 에너지 준위는 –5.34 eV와 -3.54 eV 이다.

In this study, an electro-catalyst of Pt nanoparticles supported by polypyrrole-functionalized graphene (Pt/PPy-reduced graphene oxide [RGO]) is reported. The Pt nanoparticles are deposited on the PPy-RGO composite by chemical reduction of H2PtCl6 using NaBH4. The presence of graphene (RGO) caused higher activity. This might have been due to increased electro-chemically accessible surface areas, increased electronic conductivity, and easier charge-transfer at polymer-electrolyte interfaces, allowing higher dispersion and utilization of the deposited Pt nano-particles. Microstructure, morphology and crystallinity of the synthesized materials were investigated using X-ray diffraction and transmission electron microscopy. The results showed successful deposition of Pt nano-particles, with crystallite size of about 2.7 nm, on the PPy-RGO support film. Catalytic activity for methanol electro-oxidation in fuel cells was investigated using cyclic voltammetry. The fundamental electrochemical test results indicated that the electro-catalytic activity, for methanol oxidation, of the Pt/PPy-RGO combination was much better than for commercial catalyst.

Single crystalline Cu nanowires with controlled diameters and aspect ratios have been synthesized using electrochemical deposition within confined nanochannels of a porous anodic aluminium oxide(AAO) template. The diameters of nano-sized cylindrical pores in AAO template were adjusted by controlling the anodization conditions. Cu nanowires with diameters of approximately 38, 99, 274 nm were synthesized by the electrodeposition using the AAO templates. The crystal structure, morphology and microstructure of the Cu nanowires were systematically investigated using XRD, FE-SEM, TEM and SAED. Investigation results revealed that the Cu nanowires had the controlled diameter, high aspect ratio and single crystalline nature.

In this work, iron oxide (Fe3O4) nanoparticles were deposited on multi-walled carbon nanotubes (MWNTs) by a simple chemical coprecipitation method and Fe3O4-decorated MWNTs (Fe-MWNTs)/polypyrrole (PPy) nanocomposites (Fe-MWNTs/PPy) were prepared by oxidation polymerization. The effect of the PPy on the electrochemical properties of the Fe-MWNTs was investigated. The structures characteristics and surface properties of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrochemical performances of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were determined by cyclic voltammetry and galvanostatic charge/discharge characteristics in a 1.0 M sodium sulfite electrolyte. The results showed that the Fe-MWNTs/PPy electrode had typical pseudo-capacitive behavior and a specific capacitance significantly greater than that of the Fe-MWNT electrode, indicating an enhanced electrochemical performance of the Fe-MWNTs/PPy due to their high electrical properties.

Mass production-capable powder was synthesized for use as cathode material in state-of-the-art lithium-ion batteries. These batteries are main powder sources for high tech-end digital electronic equipments and electric vehicles in the near future and they must possess high specific capacity and durable charge-discharge characteristics. Amorphous silicone was quite superior to crystalline one as starting material to fabricate silicone oxide with high reactivity between precursors of sol-gel type reaction intermediates. The amorphous silicone starting material also has beneficial effect of efficiently controlling secondary phases, most notably . Lastly, carbon was coated on powders by using sucrose to afford some improved electrical conductivity. The carbon-coated cathode material was further characterized using SEM, XRD, and galvanostatic charge/discharge test method for morphological and electrochemical examinations. Coin cell was subject to 1.5-4.8 V at C/20, where 74 mAh/g was observed during primary discharge cycle.

We synthesized porous Co3O4/RuO2 composite using the soft template method. Cetyl trimethyl ammonium bromide (CTAB) was used to make micell as a cation surfactant. The precipitation of cobalt ion and ruthenium ion for making porosity in particles was induced by OH- ion. The porous Co3O4/RuO2 composite was completely synthesiszed after anealing until 250˚C at 3˚C/min. From the XRD ananysis, we were able to determine that the porous Co3O4/RuO2 composite was comprised of nanoparticles with low crystallinity. The shape or structure of the porous Co3O4/RuO2 composite was studied by FE-SEM and FE-TEM. The size of the porous Co3O4/RuO2 composite was 20~40 nm. From the FE-TEM, we were able to determine that porous cavities were formed in the composite particles. The electrochemical performance of the porous Co3O4/RuO2 composite was measured by CV and charge-discharge methods. The specific capacitances, determined through cyclic voltammetry (CV) measurement, were ~51, ~47, ~42, and ~33 F/g at 5, 10, 20, and 50 mV/sec scan rates, respectively. The specific capacitance through charge-discharge measurement was ~63 F/g in the range of 0.0~1.0 V cutoff voltage and 50 mAh/g current density.

WCl6-EtAlCl2 촉매계를 이용하여 비교적 큰 분자량을 갖는 폴리(페닐아세틸렌)을 합성하였다. 중합반응이 잘 진행되었으며 중합수율은 81%였다. 합성한 폴리(페닐아세틸렌) 분자구조를 NMR(1H-,13C-), IR, UV-visible, 원소분석 등으로 분석한 결과 페닐 치환기를 갖는 공액구조 고분자가 합성되었음을 확인할 수 있었다. 아울러 332 nm의 빛으로 여기시킬 경우 PL 최대 peak는 424 nm에서 관찰되었는데, 이는 2.93 eV의 광 에너지에 해당한다. 이 고분자의 순환 전압전류 그림은 도핑과 탈도핑사이에서 비가역적인 전기화학적 거동을 보여주었다. 이 고분자의 전기화학적 과정이 매우 안정하였으며, 스캔속도에 따른 산화전류 밀도 실험으로부터 이 고분자의 산화-환언 과정은 확산-제어과정에 따르는 것으로 분석되었다.

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, TiCl4·YCl3 solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical TiO2 precursor. Then, the Li4Ti5O12 was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical TiO2 precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which Li4Ti5O12 spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at 50˚C for 30 minutes and at 850˚C for 6 hours heat treatment time were optimized. Li4Ti5O12 was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.

The benzophenone derivatives(4-CH3O-4'-NO2 and 3,4'-di-NO2) are synthesized by the Fridel-Craft acylation and the nitration method. Electrochemical redox potentials of the benzophenone derivatives (4-CH3O, H, 3-Cl, 3-NO2, 4-NO2, 4-CH3O-4'-NO2, 3,4'-di-NO2) are measured by using cyclic voltammometry. In the relationship of summing Hammett value and redox potential, we find a proportional constant(σ) that shows a good relation with an electrochemical property and a reactivity of the benzophenone derivatives. The benzophenone substituted with the electron donating groups(4-OCH3 and 4-OCH3-4'-NO2) are higher the energy in the LUMO level, then increasing a band-gap energy(Eg), their Egs are obtained as a 3.94 eV and 3.59 eV, respectively.

Aluminum was anodized in a H2SO4 solution, and titanium (IV) oxide (TiO2) was electrodeposited into nanopores of anodic porous alumina in a mixed solution of TiOSO4 and (COOH)2. The photocatalytic activity of the prepared film was analyzed for photodegradation of methylene blue aqueous solution. Consequently, we found it was possible to electrodeposit TiO2 onto anodic porous alumina, and synthesized it into the nanopores by hydrolysis of a titanium complex ion under AC 8-9 V when film thickness was about 15-20μm. The photocatalytic activity of TiO2-loaded anodic porous alumina (TiO2/Al2O3) at an impressed voltage of 9 V was the highest in every condition, being about 12 times as high as sol-gel TiO2 on anodic porous alumina. The results revealed that anodic porous alumina is effective as a substrate for photocatalytic film and that high-activity TiO2 film can be prepared at low cost.