Name: Microwave-Assisted Synthesis of &#945;-Ni(OH)2 Nanosheets
Uploaded: 2023-08-18T14:20:00
Description: Watch this Scientific Journal Video about Microwave-Assisted Synthesis of α-NiOH2 Nanosheets at JoVE.com

microwave-assisted synthesis of &#945;-ni(oh)2 nanosheets

Nikel Hidroksit Nanotabakaların Mikrodalga Sentezi ve Karakterizasyonu

Nickel hydroxide, Ni(OH)2, is used for numerous applications including nickel-zinc and nickel-metal hydride batteries1,2,3,4, fuel cells4, water electrolyzers4,5,6,7,8,9, supercapacitors4, photocatalysts4, anion exchangers10, and many other analytical, electrochemical, and sensor applications4,5. Ni(OH)2 has two predominant crystal structures: &#946;-Ni(OH)2 and &#945;-Ni(OH)211. &#946;-Ni(OH)2 adopts a brucite-type Mg(OH)2 crystal structure, while &#945;-Ni(OH)2 is a turbostratically layered form of &#946;-Ni(OH)2 intercalated with residual anions and water molecules from the chemical synthesis4. Within &#945;-Ni(OH)2, the intercalated molecules are not within fixed crystallographic positions but have a degree of orientational freedom, and also function as an interlayer glue stabilizing the Ni(OH)2 layers4,12. The interlayer anions of &#945;-Ni(OH)2 affect the average Ni oxidation state13 and influence the electrochemical performance of &#945;-Ni(OH)2 (relative to &#946;-Ni(OH)2) toward battery2,13,14,15, capacitor16, and water-electrolysis applications17,18.
Ni(OH)2 can be synthesized by chemical precipitation, electrochemical precipitation, sol-gel synthesis, or hydrothermal/solvothermal synthesis4. Chemical precipitation and hydrothermal synthesis routes are widely utilized in the production of Ni(OH)2, and different synthetic conditions alter the morphology, crystal structure, and electrochemical performance. The chemical precipitation of Ni(OH)2 involves adding a highly basic solution to an aqueous nickel (II) salt solution. The phase and crystallinity of the precipitate are determined by the temperature and&#160;identities&#160;and concentrations of the nickel (II) salt and&#160;basic solution used4.
Hydrothermal synthesis of Ni(OH)2 involves heating an aqueous solution of precursor nickel (II) salt in a pressurized reaction vial, allowing the reaction to proceed at higher temperatures than ordinarily allowed under ambient pressure4. Hydrothermal reaction conditions typically favor &#946;-Ni(OH)2, but &#945;-Ni(OH)2 can be synthesized by (i) using an intercalation agent, (ii) using a non-aqueous solution (solvothermal synthesis), (iii) lowering the reaction temperature, or (iv) including urea in the reaction, resulting in ammonia-intercalated &#945;-Ni(OH)24. The hydrothermal synthesis of Ni(OH)2 from nickel salts occurs via a two-step process that involves a hydrolysis reaction (equation 1) followed by an olation condensation reaction (equation 2).19
[Ni(H2O)N]2+ + hH2O &#8596; [Ni(OH)h(H2O) N-h](2-h)++ hH3O+ (1)
Ni-OH + Ni-OH2 Ni-OH-Ni + H2O (2)
Microwave chemistry has been used for the one-pot synthesis of a wide variety of nanostructured materials and is based on the ability of a specific molecule or material to convert microwave energy into heat20. In conventional hydrothermal reactions, the reaction is initiated by the direct absorption of heat through the reactor. In contrast, within microwave-assisted hydrothermal reactions, the heating mechanisms are dipolar polarization of the solvent oscillating in a microwave field and ionic conduction generating localized molecular friction20. Microwave chemistry can increase the reaction kinetics, selectivity, and yield of chemical reactions20, making it of significant interest for a scalable, industrially viable method to synthesize Ni(OH)2.
For alkaline battery cathodes, the &#945;-Ni(OH)2 phase provides improved electrochemical capacity compared with the &#946;-Ni(OH)2 phase13, and synthetic methods to synthesize &#945;-Ni(OH)2 are of particular interest. &#945;-Ni(OH)2 has been synthesized by a variety of microwave-assisted methods, which include microwave-assisted reflux21,22, microwave-assisted hydrothermal techniques23,24, and microwave-assisted base-catalyzed precipitation25. The inclusion of urea within the reaction solution significantly influences the reaction yield26, mechanism26,27, morphology, and crystal structure27. The microwave-assisted decomposition of urea was determined to be a critical component for obtaining &#945;-Ni(OH)227. Water content in an ethylene glycol-water solution has been shown to impact the morphology of microwave-assisted synthesis of &#945;-Ni(OH)2 nanosheets24. The reaction yield of &#945;-Ni(OH)2, when synthesized by a microwave-assisted hydrothermal route using an aqueous nickel nitrate and urea solution, was found to depend on the solution pH26. A prior study of microwave synthesized &#945;-Ni(OH)2 nanoflowers using a precursor solution of EtOH/H2O, nickel nitrate, and urea found that temperature (in the range of 80-120 &#176;C) was not a critical factor, provided the reaction is conducted above the urea hydrolysis temperature (60 &#176;C)27. A recent paper that studied the microwave synthesis of Ni(OH)2 using a precursor solution of nickel acetate tetrahydrate, urea, and water found that at a temperature of 150 &#176;C, the material contained both &#945;-Ni(OH)2 and &#946;-Ni(OH)2 phases, which indicates that temperature can be a critical parameter in the synthesis of Ni(OH)228.
Microwave-assisted hydrothermal synthesis can be used to produce high-surface area &#945;-Ni(OH)2 and &#945;-Co(OH)2 by using a precursor solution composed of metal nitrates and urea dissolved in an ethylene glycol/H2O solution12,29,30,31. Metal-substituted &#945;-Ni(OH)2 cathode materials for alkaline Ni-Zn batteries were synthesized using a scaled-up synthesis designed for a large-format microwave reactor12. Microwave-synthesized &#945;-Ni(OH)2 was also used as a precursor for obtaining &#946;-Ni(OH)2 nanosheets12, nickel-iridium nanoframes for oxygen evolution reaction (OER) electrocatalysts29, and bifunctional oxygen electrocatalysts for fuel cells and water electrolyzers30. This microwave reaction route has also been modified to synthesize Co(OH)2 as a precursor for cobalt-iridium nanoframes for acidic OER electrocatalysts31 and bifunctional electrocatalysts30. Microwave-assisted synthesis was also used to produce Fe-substituted &#945;-Ni(OH)2 nanosheets, and the Fe substitution ratio alters the structure and magnetization32. However, a step-by-step procedure for microwave synthesis of &#945;-Ni(OH)2 and the evaluation of how varying reaction time and temperature within a water-ethylene glycol solution affects the crystalline structure, surface area, and porosity, and local environment of interlayer anions within the material&#160;has not been previously reported.
This protocol establishes procedures for high-throughput microwave synthesis of &#945;-Ni(OH)2 nanosheets using a rapid and scalable technique. The effect of reaction temperature and time were varied and evaluated using in situ reaction monitoring, scanning electron microscopy, energy dispersive X-ray spectroscopy, nitrogen porosimetry, powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy to understand the effects of synthetic variables on reaction yield, morphology, crystal structure, pore size, and local coordination environment of &#945;-Ni(OH)2 nanosheets.

Yazar Spotlight: Nikel Hidroksit Nanotabakalarının Hızlı, Mikrodalga Destekli Hidrotermal Sentezi 

Mikrodalga Sentez Koşullarının Nikel Hidroksit Nano Levhaların Yapısına Etkisi

Watch this Scientific Journal Video about Microwave-Assisted Synthesis of α-NiOH2 Nanosheets at JoVE.com

Microwave-Assisted Synthesis of &#945;-Ni(OH)2 Nanosheets  

α-Ni(OH)2 Nanotabakaların Mikrodalga Destekli Sentezi

105 mililitre etilen glikol ve 15 mililitre ultra saf suyu karıştırarak öncü çözeltiyi hazırlamaya başlayın. Daha sonra 4.1 gram üri ekleyin ve 5.0 gram nikel nitrat heksahidrat ekleyin ve çözeltiyi kapatın. Öncü çözeltiyi 30 dakika boyunca 40 kilohertz frekansında ve nabızsız tam güçte buz ve su ile dolu bir banyo sonikatöründe sonikleştirin.20 mililitre sonik öncü çözeltiyi bir PTFE karıştırma çubuğu ile donatılmış bir mikrodalga reaksiyon şişesine aktarın. PTFE astarlı bir kilitleme kapağı kullanarak reaksiyon kabını kapatın. Şişeyi mikrodalga reaktörün içine yerleştirin ve reaktör programını, istenen sıcaklığa ulaşılana kadar maksimum güç uygulayan mümkün olduğunca hızlı olacak şekilde ayarlayın.Daha sonra, reaksiyon sıcaklığını 13 ila 30 dakika korumak için değişken güç uygulayın. Reaksiyonun tamamlanmasının ardından, çözelti sıcaklığı 55 santigrat dereceye ulaşana kadar reaksiyon odasını basınçlı hava ile havalandırın. Reaksiyon sonrası çözeltiyi 50 mililitrelik santrifüj tüplerine aktarın.Tüpleri oda sıcaklığında dört dakika santrifüjleyin ve süpernatanı boşaltın. Elde edilen nikel hidroksit nano tabakalarını 25 mililitre ultra saf su içinde yeniden süspanse edin ve daha önce gösterildiği gibi bir kez daha santrifüjleyin. Süpernatanı boşalttıktan sonra, olası kontaminasyonu en aza indirmek için santrifüj tüplerini gözenekli bir örtü görevi gören bir kağıt mendil veya kağıt havluyla örtün.Son olarak, nano tabakaları ortam atmosferi altında 70 santigrat derecede 21 saat boyunca örnek bir fırında kurutun. 120 santigrat derecede, üretilen maksimum reaksiyon basıncı, inç kare veya PSI başına dokuz ila 11.5 pound idi. 180 santigrat derecede ise 138 PSI'ye yükseldi.Reaksiyon sıcaklığının 120 santigrat dereceden 180 santigrat dereceye çıkarılması, reaksiyon sonrası süpernatan rengini yeşilden maviye değiştirdi. C2'de, 180 santigrat derecedeki reaksiyonun fotoğrafları, reaksiyon sona erdiğinde bulanık yeşil bir renk gösterdi, ancak reaksiyon soğudukça bulanık maviye dönüştü. Santrifüjleme, yıkama ve kurutmadan sonra, zaman ve sıcaklıktan bağımsız olarak tüm reaksiyonlar yeşil bir toz üretti.180 santigrat derece reaksiyonunun süpernatantının pH'ı, 120 santigrat derece reaksiyon süpernatantlarına göre çok daha yüksekti. 180 santigrat derece reaksiyonu ayrıca 120 santigrat derecedeki reaksiyonlardan çok daha yüksek bir verim kaydetti.

Research

JoVE Journal

Chemistry

Microwave-Assisted Synthesis of &#945;-Ni(OH)2 Nanosheets

Effect of Microwave Synthesis Conditions on the Structure of Nickel Hydroxide Nanosheets

A protocol for rapid, microwave-assisted hydrothermal synthesis of nickel hydroxide nanosheets under mildly acidic conditions is presented, and the effect ...

Kimya

Characterization and Analysis of &#945;-Ni(OH)2 Nanosheets

Characterization and Analysis of &#945;-Ni(OH)2 Nanosheets  

α-Ni(OH)2 Nanotabakalarının Karakterizasyonu ve Analizi