An overview on chemical processes for synthesis of graphene from waste carbon resources

Abhilash,Swetha Vaidyanathan,Meshram Pratima 한국탄소학회 2022 Carbon Letters Vol.32 No.3

Graphene, the wonder material has brought a revolutionary change in the field of nanotechnology owing to its tremendous properties. Though different methods for the synthesis of graphene have been reported, the chemical synthesis route offers a scalable and high-volume production of graphene. The unreliability of graphite and hydrocarbon resources to serve as steady supplies of carbon resources and further in the synthesis of graphene has led to the exploration and use of alternative low-cost carbon-rich resources (coal, graphite, rice husk, sugarcane bagasse, peanut shells, waste tyres, etc.) as precursors for graphene synthesis. The use of untraditional carbon resources reduces dependence on traditional resources (coal, graphite), reduced cost, increased reliability, and provides a way for the management of waste biomass. This review hence focuses on the synthesis of graphene by the most common approachable method, oxidation–reduction of graphite, along with the various other chemical methods of synthesis from varied carbon resources.

Chemical-hydrothermal synthesis of oval-shaped graphene/ZnO quantum hybrids and their photocatalytic performances

Van Thuan, Doan,Nguyen, Tri Khoa,Kim, Soon-Wook,Chung, Jin Suk,Hur, Seung Hyun,Kim, Eui Jung,Hahn, Sung Hong,Wang, Mingsong Elsevier 2017 CATALYSIS COMMUNICATIONS - Vol.101 No.-

<P><B>Abstract</B></P> <P>Oval-shaped graphene/ZnO quantum hybrid (GZQH) is synthesized via chemical-hydrothermal method and tested for the photoenhanced selective reduction of nitroarenes. A facile molecular fusion process is employed to produce graphene quantum dots (GQDs) from pyrene, which is followed by hydrothermal treatment with embryonic ZnO quantum dots (5nm in size) to yield the GZQHs. Zn<SUP>2+</SUP> ions on ZnO embryo react with a functional group of graphene, which forms Zn-O-C bonding leading to highly crystalline quantum hybrids with uniform interface. The GZQHs have a quenched photoluminescence intensity as compared to the GQDs (2nm in size) due to electron transfer at the graphene-ZnO interface. Hydrogen molecules dissociate into hydrogen atoms by photogenerated electrons which transfer and perturb at the interface under UV irradiation. The GZQHs exhibit an excellent UV-induced catalytic performance for the selective reduction of nitroarenes. The effect of ZnO:graphene ratio on reduction reaction rate constant is also investigated.</P> <P><B>Highlight</B></P> <P> <UL> <LI> Excellent hydrogenation reduction of noble-metal-absent catalyst: Graphene and ZnO. </LI> <LI> Graphene and zinc oxide composite at the quantum scale particle synthesis. </LI> <LI> Hydrogen dissociation at G/ZnO interface and spillover to graphene. </LI> <LI> UV stimulated electron transfer and perturbation within Gr/ZnO. </LI> <LI> Catalytic dependence of NaBH<SUB>4</SUB> and Gr/ZnO ratio and reduction of different nitroarenes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

n-Type NanostructuredThermoelectric Materials Preparedfrom Chemically Synthesized Ultrathin Bi₂Te₃ Nanoplates

Son, Jae Sung,Choi, Moon Kee,Han, Mi-Kyung,Park, Kunsu,Kim, Jae-Yeol,Lim, Seong Joon,Oh, Myunghwan,Kuk, Young,Park, Chan,Kim, Sung-Jin,Hyeon, Taeghwan American ChemicalSociety 2012 Nano letters Vol.12 No.2

<P>We herein report on the large-scale synthesis of ultrathin Bi2Te3 nanoplates and subsequent spark plasma sintering to fabricate n-type nanostructured bulk thermoelectric materials. Bi2Te3 nanoplates were synthesized by the reaction between bismuth thiolate and tri-n-octylphosphine telluride in oleylamine. The thickness of the nanoplates was similar to 1 nm, which corresponds to a single layer in Bi2Te3 crystals. Bi2Te3 nanostructured bulk materials were prepared by sintering of surfactant-removed Bi2Te3 nanoplates using spark plasma sintering. We found that the grain size and density were strongly dependent on the sintering temperature, and we investigated the effect of the sintering temperature on the thermoelectric properties of the Bi2Te3 nanostructured bulk materials. The electrical conductivities increased with an increase in the sintering temperature, owing to the decreased interface density arising from the grain growth and densification. The Seebeck coefficients roughly decreased with an increase in the sintering temperature. Interestingly, the electron concentrations and mobilities strongly depended on the sintering temperature, suggesting the potential barrier scattering at interfaces and the doping effect of defects and organic residues. The thermal conductivities also increased with an increase in the sintering temperature because of grain growth and densification. The maximum thermoelectric figure-of-merit, ZT, is 0.62 at 400 K, which is one of the highest among the reported values of n-type nanostructured materials based on chemically synthesized nanoparticles. This increase in ZT shows the possibility of the preparation of highly efficient thermoelectric materials by chemical synthesis.</P>

Ion exchange: an advanced synthetic method for complex nanoparticles

하돈형,Yun-Kun Hong,Yoonsu Park,Geonhee Cho 나노기술연구협의회 2019 Nano Convergence Vol.6 No.17

There have been tremendous efforts to develop new synthetic methods for creating novel nanoparticles (NPs) with enhanced and desired properties. Among the many synthetic approaches, NP synthesis through ion exchange is a versatile and powerful technique providing a new pathway to design complex structures as well as metastable NPs, which are not accessible by conventional syntheses. Herein, we introduce kinetic and thermodynamic factors controlling the ion exchange reactions in NPs to fully understand the fundamental mechanisms of the reactions. Additionally, many representative examples are summarized to find related advanced techniques and unique NPs constructed by ion exchange reactions. Cation exchange reactions mainly occur in chalcogenide compounds, while anion exchange reactions are mainly involved in halogen (e.g. perovskite) and metal-chalcogenide compounds. It is expected that NP syntheses through ion exchange reactions can be utilized to create new devices with the required properties by virtue of their versatility and ability to tune fine structures.

Direct Integration of Polycrystalline Graphene into Light Emitting Diodes by Plasma-Assisted Metal-Catalyst-Free Synthesis

Kim, Yong Seung,Joo, Kisu,Jerng, Sahng-Kyoon,Lee, Jae Hong,Moon, Daeyoung,Kim, Jonghak,Yoon, Euijoon,Chun, Seung-Hyun American Chemical Society 2014 ACS NANO Vol.8 No.3

<P>The integration of graphene into devices is a challenging task because the preparation of a graphene-based device usually includes graphene growth on a metal surface at elevated temperatures (∼1000 °C) and a complicated postgrowth transfer process of graphene from the metal catalyst. Here we report a direct integration approach for incorporating polycrystalline graphene into light emitting diodes (LEDs) at low temperature by plasma-assisted metal-catalyst-free synthesis. Thermal degradation of the active layer in LEDs is negligible at our growth temperature, and LEDs could be fabricated without a transfer process. Moreover, <I>in situ</I> ohmic contact formation is observed between DG and p-GaN resulting from carbon diffusion into the p-GaN surface during the growth process. As a result, the contact resistance is reduced and the electrical properties of directly integrated LEDs outperform those of LEDs with transferred graphene electrodes. This relatively simple method of graphene integration will be easily adoptable in the industrialization of graphene-based devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-3/nn405477f/production/images/medium/nn-2013-05477f_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn405477f'>ACS Electronic Supporting Info</A></P>

Photon-Triggered Current Generation in Chemically-Synthesized Silicon Nanowires

Kim, Jungkil,Kim, Ha-Reem,Lee, Hoo-Cheol,Kim, Kyoung-Ho,Hwang, Min-Soo,Lee, Jung Min,Jeong, Kwang-Yong,Park, Hong-Gyu American Chemical Society 2019 NANO LETTERS Vol.19 No.2

<P>A porous Si segment in a Si nanowire (NW), when exposed to light, generates a current with a high on/off ratio. This unique feature has been recently used to demonstrate photon-triggered NW devices including transistors, logic gates, and photodetection systems. Here, we develop a reliable and simple procedure to fabricate porous Si segments in chemically synthesized Si NWs for photon-triggered current generation. To achieve this, we employ 100 nm-diameter chemical-vapor-deposition grown Si NWs that possess an n-type high doping level and extremely smooth surface. The NW regions uncovered by electron-beam resist become selectively porous through metal-assisted chemical etching, using Ag nanoparticles as a catalyst. The contact electrodes are then fabricated on both ends of such NWs, and the generated current is measured when the laser is focused on the porous Si segment. The current level is changed by controlling the power of the incident laser and bias voltage. The on/off ratio is measured up to 1.5 × 10<SUP>4</SUP> at a forward bias of 5 V. In addition, we investigate the porous-length-dependent responsivity of the NW device with the porous Si segment. The responsivity is observed to decrease for porous segment lengths beyond 360 nm. Furthermore, we fabricate nine porous Si segments in a single Si NW and measure the identical photon-triggered current from each porous segment; this single NW device can function as a high-resolution photodetection system. Therefore, our fabrication method to precisely control the position and length of the porous Si segments opens up new possibilities for the practical implementation of programmable logic gates and ultrasensitive photodetectors.</P> [FIG OMISSION]</BR>

메탄올 생산용 고활성 Cu/ZnO 촉매 합성방법

정천우 ( Cheonwoo Jeong ),서영웅 ( Young-woong Suh ) 한국공업화학회 2016 공업화학 Vol.27 No.6

대기 중 이산화탄소의 재활용 기술과 재생에너지에 의한 물 분해 기술의 접목이 최근 가능해지면서 메탄올은 많은 관심을 받고 있다. 경제성이 유리하도록 메탄올 경제를 실현하기 위해서는 고활성 메탄올 합성 촉매를 제조하여야 하며, 이를 위해서는 논리적인 접근법이 필요하다. 공침법을 통해 제조하는 Cu/ZnO 기반의 촉매는 침전, 숙성, 여과, 세척, 건조, 소성, 환원 등의 복잡한 단계로 제조되며, 100년의 역사를 가지고 있음에도 불구하고 최근에야 침전 화학과 촉매 나노구조에 대한 기초적인 이해가 이루어지고 있다. 이에 본 고에서는 단계별로 합성 변수가 침전, 소성, 환원상태 물질의 물성에 미치는 영향에 대한 최근 결과들을 리뷰하고, 화학적 기억 효과라고 부르는 이들 물성들과 최종촉매의 활성 사이의 관련성을 논의하였다. 제조 변수별 설명은 메탄올 합성을 위한 Cu/ZnO 기반 고활성 촉매를 제조하는 방법에 초점이 맞추어져 있다. 논의된 합성 전략은 공침법을 기반으로 하는 타 금속 또는 금속 산화물 담지 촉매의 제조에 활용 가능할 것으로 판단된다. In recent years, methanol has attracted much attention since it can be cleanly manufactured by the combined use of atmospheric CO₂ recycling and water splitting via renewable energy. For the concept of “methanol economy”, an active methanol synthesis catalyst should be prepared in a sophisticated manner rather than by empirical optimization approach. Even though Cu/ZnO-based catalysts prepared by coprecipitation are well known and have been extensively investigated even for a century, fundamental understanding on the precipitation chemistry and catalyst nanostructure has recently been achieved due to complexity of the necessary preparation steps such as precipitation, ageing, filtering, washing, drying, calcination and reduction. Herein we review the recent reports regarding the effects of various synthesis variables in each step on the physicochemical properties of materials in precursor, calcined and reduced states. The relationship between these characteristics and the catalytic performance will also be discussed because many variables in each step strongly influence the final catalytic activity, called “chemical memory”. All discussion focuses on how to prepare a highly active Cu/ZnO-based catalyst for methanol synthesis. Furthermore, the preparation strategy we deliver here would be utilized for designing other coprecipitation-derived supported metal or metal oxide catalysts.

수소 캐리어를 위한 CO₂-free 암모니아 합성기술 동향

김지현(Jihyeon Kim),김진호(Jin-Ho Kim),김효식(Hyo Sik Kim),류재홍(Jae-Hong Ryu),강석환(Suk-Hwan Kang),박새미(Sae-Mi Park),정석용(Suk-Yong Jung),이수출(Soo-Chool Lee) 한국에너지기후변화학회 2020 에너지기후변화학회지 Vol.15 No.1

Fossil fuel is a material that is actively used and occupies a significant portion of energy sources. However, environmental pollution occurs due to the use of fossil fuel, research has been actively conducted around the world to develop an alternative energy source. Particularly, as interest in hydrogen energy increases, interest in a medium capable of storing and transporting it also increases. Ammonia, which will be discussed in this paper, not only acts as a storage and transport medium for hydrogen, but is also used as a direct fuel in internal combustion engines or gas turbines due to the combustion characteristics of ammonia. In general, a ton of ammonia requires a significant amount of energy (9 ~ 15 MWh) to be produced and energy loss can occur through the conversion process. Nevertheless, the importance of ammonia as an energy carrier in recent years has been expanding R&D and investment mainly in Australia and Japan. This paper introduces the current state and level of technology developments such as thermal catalyst, electrocatalyst, photocatalyst and chemical roofing for ammonia synthesis.

Improvement of photocatalytic behavior of chemical-vapor-synthesized TiO₂ nanopowders by post-heat treatment

박훈,HyunSeock Jie,채근화,박종구,Masakazu Anpo,Dok-Yol Lee 한국물리학회 2008 Current Applied Physics Vol.8 No.6

Anatase-type TiO₂ nanopowders less than 10 nm in average diameter were synthesized by a chemical vapor synthesis method. The TiO₂ nanopowders showed very poor photocatalytic properties, in spite of their large surface area. With subsequent heat treatment of the TiO₂ powders, their photocatalytic properties determined by measuring the degradation of 2-propanol were improved at temperatures up to 600˚C and then diminished along with formation of a rutile phase. This improvement in the photocatalytic properties of TiO₂ nanopowders was attributed to both a morphology change and a change in the electronic surface characteristics of TiO₂ particles during heat treatment. Anatase-type TiO₂ nanopowders less than 10 nm in average diameter were synthesized by a chemical vapor synthesis method. The TiO₂ nanopowders showed very poor photocatalytic properties, in spite of their large surface area. With subsequent heat treatment of the TiO₂ powders, their photocatalytic properties determined by measuring the degradation of 2-propanol were improved at temperatures up to 600˚C and then diminished along with formation of a rutile phase. This improvement in the photocatalytic properties of TiO₂ nanopowders was attributed to both a morphology change and a change in the electronic surface characteristics of TiO₂ particles during heat treatment.

Development of a kinetic model for Fischer–Tropsch synthesis over Co/Ni/Al2O3 catalyst

Farhad Fazlollahi,Majid Sarkari,Akbar Zare,Ali Akbar Mirzaei,Hossein Atashi 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.4

In the present research an active Co–Ni/Al2O3 catalyst was prepared by impregnation method for synthesis of light olefins in Fischer–Tropsch synthesis. After studying the effects of using optimized operating conditions on catalyst performance, the kinetic experimental study was performed in a differential micro-fixed-bed-reactor by altering reaction temperature (230–270 8C), pressure (2–12 bar),gas hourly space velocity (2000–7200 h-1) and H2/CO feed molar ratio (1–3). Based on Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach, seven different two-parameter kinetic models were considered. The kinetic data of this study were fitted accurately by a simple form -rCO ¼APCOPH2 =ð1 þ bPCOP0:5H2Þ2 that assumed the following kinetically relevant steps, where CO dissociates via interaction with adsorbed hydrogen; the first hydrogenation step of the surface carbon was reversible and fast, while the second one was slow and rate determining. The kinetic parameters were determined using Levenberg–Marquardt (LM) method and the apparent activation energy and heat of adsorption were 78.70 kJ/mol and -14.16 kJ/mol, respectively.