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

characterization and analysis of &#945;-ni(oh)2 nanosheets

Nickel Hydroxide Nanosheets의 마이크로파 합성 및 특성화

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.

저자 스포트라이트: 수산화니켈 나노시트의 신속한 마이크로파 보조 열수 합성 

마이크로파 합성 조건이 수산화니켈 나노시트의 구조에 미치는 영향

Watch this Scientific Journal Video about Characterization and Analysis of α-NiOH2 Nanosheets at JoVE.com

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

α-Ni(OH)2 나노시트의 특성화 및 분석

SEM 및 EDS에 의한 마이크로파 합성 수산화 니켈 나노 시트의 형태 및 조성을 특성화하려면 수조 초음파 발생기를 사용하여 에탄올 1 밀리리터에 소량의 수산화 니켈 분말을 현탁시켜 샘플을 준비합니다. 그런 다음 수산화니켈과 에탄올 혼합물을 SEM 스텁에 떨어뜨리고 SEM 현미경 사진 및 EDS 스펙트럼을 수집하기 전에 섭씨 70도의 샘플 오븐에서 스텁을 가열하여 에탄올을 증발시킵니다. 나노 시트의 표면적과 다공성을 측정하기 위해 25 밀리그램의 수산화 니켈 나노 시트를 샘플 튜브에 첨가하십시오.섭씨 120도에서 16시간 동안 진공 상태에서 사전 분석 탈기 및 건조 절차를 수행합니다. 마지막으로 시료 튜브를 탈기 포트에서 분석 포트로 옮겨 질소 등온선을 수집합니다. X선 회절 또는 XRD를 사용한 구조 분석의 경우 배경이 없는 분말 XRD 홀더의 샘플 웰을 수산화니켈로 채웁니다.0.01 단계 단위로 2도에서 80도 사이의 2-세타 사이의 구리 K-알파 방사선 소스를 사용하여 분말 X선 회절도를 수집합니다. 감쇠된 총 반사율 또는 ATR 부착물을 푸리에 변환 적외선 또는 FTIR 분광기에 장착합니다. 두 개의 유리 슬라이드 사이에 소량의 수산화니켈 분말을 눌러 펠릿을 만듭니다.그 때 실리콘 ATR 결정에 니켈 수산화물 펠릿을 두고 404 사이 FTIR 스펙트럼, 4개의 상호 센티미터의 해결책을 가진 16의 개인적인 검사의 평균으로 000의 상호 센티미터를 얻는다. SEM은 마이크로파 합성 수산화 니켈이 무작위로 짜여진 초박형 나노 시트 응집체로 구성되어 있음을 밝혔습니다. 그러나 반응 온도를 섭씨 120도에서 180도로 높이면 응집체에서 개별 나노시트의 측면 시트 치수가 증가했습니다.또한, 섭씨 120도에서 반응 시간을 13분에서 30분으로 증가시킴으로써, 핵화된 응집체 크기가 약 3미크론에서 5미크론으로 증가하였다. EDS는 합성된 모든 나노시트 내에서 니켈, 산소, 탄소 및 질소의 균일한 분포를 보여주었습니다. 나노 시트는 그램 당 61에서 85 평방 미터 범위의 BET 표면적, 21에서 35 옹스트롬의 평균 기공 직경, 그램 당 0.4에서 0.6 입방 센티미터의 누적 불량 부피를 가졌습니다.세 가지 마이크로파 합성 샘플 모두의 XRD 패턴은 알파 니켈 수산화물의 특징적인 피크를 보여주었습니다. 그러나 반응 시간과 온도는 001 비행기의 이동에 의해 입증 된 것처럼 피크에 영향을 미쳤습니다. 마이크로파 합성 나노시트의 ATR-FTIR 스펙트럼은 특징적인 니켈 산화물 격자 모드를 나타냈다.리간드 및 구조 분자, 시안산염 띠 및 알파 수산화물 격자 모드의 모드. 반응 온도를 섭씨 120도에서 180도로 높이면 시안산염, 질산염, 수산기 및 물 진동 모드의 주파수와 상대 강도가 변경되었습니다.

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JoVE Journal

Chemistry

Characterization and Analysis 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 ...