산화 이리듐의 물의 산화반응에 대한 버블 과전압 현상과 촉매 특성 연구

김정중,최용수,권성중,Kim, Jeong Joong,Choi, Yong Soo,Kwon, Seong Jung 한국전기화학회 2013 한국전기화학회지 Vol.16 No.2

Iridium oxide is well known as an electrocatalyst for the water oxidation. Recently, Dr. Bard's group observed the electrocatalytic behavior of individual nanoparticle of Iridium oxide using the electrochemical amplification method by detecting the single nanoparticle collisions at the ultramicroelectrode (UME). However, the electrocatalytic current is decayed as a function of time. In this study, we investigated that the reason of electrocatalytic current decay of water oxidation at Iridium oxide nanoparticles. We identified it is due to the bubble overpotential because the cyclic current decay and recovery were synchronized to the oxygen bubble growth and coming away from an Iridium disk electrode. 산화 이리듐은 물의 산화반응에 대해 좋은 전기촉매 물질로서 많은 연구가 이루어 지고 있다. 최근 전기화학적 증폭방법을 이용하여 산화 이리듐 나노입자의 개별적인 촉매특성을 연구한 결과를 보면 촉매반응에 의한 전류가 지속적으로 유지되지 않고 시간에 따라 감소하는 결과가 얻어 졌다. 이러한 촉매특성의 사라짐에 대한 원인을 규명하고자 사이즈가 큰 이리듐전극을 산화시킨 산화이리듐 전극에서 물의 산화반응을 진행시켰다. 그 결과 나노입자에서와 유사하게 전류가 감소하는 현상이 관찰되었다. 큰 전극에서의 실험에서는 발생하는 산소방울을 관찰 할 수 있었는데 산소방울의 발생 주기가 전류의 증감주기와 일치하는 것으로 보아 전류의 감소는 산소방울에 의한 버블 과전압 때문으로 생각된다.

Preparation of nanopillar array electrode of iridium oxide for high performance of pH sensor and its real‐time sweat monitoring

윤은섭,박홍준,길민식,김주은,이경균,최봉길 대한화학회 2023 Bulletin of the Korean Chemical Society Vol.44 No.6

A highly sensitive potentiometric pH sensor was developed based on nanopil-lar array electrodes of iridium oxide. The as-prepared pH sensor exhibited ahigh pH sensitivity (69.43 mV/pH), fast response time (8.1 s), and good durabil-ity (0.76 mV/h). The sensing performance of the pH sensor was maintainedunder mechanical bending and even after 1000 repetitive bending/releasingcycles. As a proof-of-concept, a wearable headband sensor was fabricated byintegrating the pH sensor with a wireless electronic module based on a printedcircuit board. The on-body test indicated that the wearable pH sensor providesreliable and stable data in the real-time monitoring of pH changes in humansweat during stationary indoor cycling. The pH sensors based on nanopillararray electrodes of iridium oxide have great potential in many portable orwearable applications in healthcare systems, non-invasive diagnostics, environ-mental analysis, and food sensors.

Nanotubular Iridium–Cobalt Mixed Oxide Crystalline Architectures Inherited from Cobalt Oxide for Highly Efficient Oxygen Evolution Reaction Catalysis

Yu, Areum,Lee, Chongmok,Kim, Myung Hwa,Lee, Youngmi American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.40

<P>Here, we report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as IrxCo1-x,O-y, where x is the relative Ir atomic content to the overall metal content. The formation of a variety of Ir Col-xOy (0 <= x <= 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterization clearly confirmed that IrxCo1-xOy polycrystalline nanocomposites had a tubular morphology consisting of Ir/IrO2 and Co3O4, where Ir, Co, and O were homogeneously distributed throughout the entire nanostructures. The facile formation of IrxCo1-xOy nanotubes was mainly ascribed to the inclination of Co3O4 to form the nanotubes during the calcination process, which could play a critical role in providing a template of tubular structure and facilitating the formation of IrO2 by being incorporated with Ir precursors. Furthermore, the electroactivity of obtained IrxCo1-xOy nanotubes was characterized for oxygen evolution reaction (OER) with rotating disk electrode voltammetry in 1 M NaOH aqueous solution. Among diverse IrxCo1-xOy, Ir0.46Co0.54Oy nanotubes showed the best OER activity (the least-positive onset potential, greatest, current density, and low Tafel slope), which was even better than that of commercial Ir/C. The Ir0.46Co0.54Oy nanotubes also exhibited a high stability in alkaline electrolyte. Expensive Ir mixed with cheap Co at an optimum ratio showed a greater OER catalytic activity than pure Ir oxide, one of the most efficient OER catalysts.</P>

Iridium Oxide–Electrodeposited Nanoporous Gold Multielectrode Array with Enhanced Stimulus Efficacy

Kim, Yong Hee,Kim, Gook Hwa,Kim, Min Sun,Jung, Sang-Don American Chemical Society 2016 NANO LETTERS Vol.16 No.11

<P>A multielectrode array (MEA) was fabricated with electrodes consisting of iridium oxide (IrOx) electrochemically deposited on nanoporous gold (NPG) to improve the moderate charge injection limit (ca. 1 mC cm(-2)) of NPG MEA. IrOx was electrodeposited by performing cyclic voltammetry with an IrOx deposition solution. The IrOx was electrodeposited on Au (EIROF/Au) and on NPG (EIROF/NPG) MEA, and the samples were analyzed in terms of the charge injection limit, charge storage capacity (CSC), and electrochemical impedance. The charge injection limit of the EIROF(100-cycled)/NPG MEA was estimated to be 2.3 mC cm(-2) by measuring the voltage transient, and this value is sufficiently greater than the neural damage threshold (ca. 1 mC cm(-2)) and is also comparable to that of sputtered IrOx films. Considering the low charge injection limit (<0.1 mC cm(-2)) for the EIROF(100-cycled)/Au MEA, the high charge injection limit for the EIROF/NPG MEA was explained to be a result of synergetic combination of the inherently large surface area of the NPG and electrically active EIROF. The EIROF(100-cycled)/NPG exhibited an impedance of 9.7 +/- 0.45 k Omega at 1 kHz and a CSC of 8 mC/cm(-2), respectively, obtained via electrochemical impedance spectroscopy and integration of the cathodic current in a cyclic voltammogram. Scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy are used to conduct an elemental mapping analysis of the cross-sectional structure of the EIROF/NPG and revealed that the EIROF had been uniformly deposited on the surface of the interconnected Au. The efficacy of the improvement in the charge injection limit of the EIROF/NPG MEA was evaluated with rat hippocampal slices. The EIROF/NPG electrodes exhibited a steeper increase in the negative peak amplitude of the field excitatory postsynaptic potentials (fEPSPs), even with an electrical stimulation of a lower amplitude (1-4 V), prolonged negative fEPSPs wave after peak response, and decreased serial reduction of fEPSPs compared to NPG MEA, all of which strongly indicate an improved charge injection for the EIROF/NPG MEA over NPG MEA.</P>

Iridium Oxide Dendrite as a Highly Efficient Dual Electro-Catalyst for Water Splitting and Sensing of H₂O₂

Kim, Soochan,Cho, Misuk,Lee, Youngkwan The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.5

<P>The synthesis and electrocatalytic performance of iridium-oxide ( IrO2) are reported. IrO2 was electrochemically deposited on the gold dendrite template prepared by the chronoamperometry. The influence of the synthetic condition on the morphology, phase composition, and accessible surface area of the IrO2 dendrites was investigated. The optimized IrO(2 d)endrites showed an excellent electrocatalytic activity toward oxygen evolution with a low overpotential of 240 mV at 5 mAcm(- 2) and to the sensing of hydrogen peroxide with a high sensitivity of 692.38 mu AmM(- 1)cm(- 2) in a wide linear range. (C) The Author(s) 2016. Published by ECS.</P>

Electrochemical properties of Ir doped NiCoOx nano structure catalyst for Enhanced Oxygen Evolution in alkaline media

이학주,박경원,박덕혜,이슬기,이우준 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

전 세계적으로 화석연료를 대체할 수 있는 친환경 에너지원으로 수소에 주목을 하고 있다. 이에 따라 전기를 사용해 물을 분해하여 수소를 발생시키는 친환경 수전해 방법이 각광받고 있다. 그 중에서도 저온에서 운용되며 수소생산속도가 빠른 Alkaline 수전해가 주목을 받고 있다. 특히 수전해의 효율을 증가시키기 위해 복잡한 매커니즘을 가지며 에너지 손실이 많이 발생하는 OER(Oxygen Evolution Reaction)에 관해 연구가 많이 진행되고 있다. 수전해의 Anode에서 주로 귀금속 산화물이 많이 사용되는데 매장량과 가격에서 문제점을 가지고 있다. 이 문제점을 극복하기 위해서 매장량이 풍부하고 가격이 저렴한 전이금속 산화물인 Cobalt와 Nickel에 관한 연구가 많이 진행되고 있다. 본 연구에서는 각각의 mono metal oxide보다 전기전도도, 촉매적 활성이 더 좋은 binary metal oxide에 Iridium 을 도핑하는 연구를 진행하였다. Hydrothermal method를 이용한 합성과정에서 nano size의 비표면적이 높은 촉매를 합성하고 alkaline 환경에서 전기화학 평가를 진행하였다.

A layered hollow sphere architecture of iridium-decorated carbon electrode for oxygen evolution catalysis

Lee, Sang Ha,Lee, Hyuck,Cho, Misuk,Lee, Youngkwan Elsevier 2017 Carbon Vol.115 No.-

<P>Here, we introduce a layered hollow sphere (LHS) architecture of iridium -decorated carbon electrode. The electrode was prepared by coating of a solution composed of graphene oxide (GO), IrC1(3), and polystyrene bead followed by subsequent pyrolysis. The morphology of the electrode was investigated according to the composition of solution, and the electrocatalytic properties were characterized. The usage of GO highly enhanced the electrochemical surface area of the electrode (by similar to 6 times). The LHS electrode also showed outstanding electrocatalytic properties: a current density of 89.99 mA/cm(2) could be obtained at a potential of 1.6 V. (C)2017 Elsevier Ltd. All rights reserved.</P>

Observation of Electrocatalytic Amplification of Iridium Oxide (IrOx) Single Nanoparticle Collision on Copper Ultramicroelectrodes

최용수,Seung Yeon Jung,Jin Woo Joo,권성중 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.8

Recently, the observation of the electrocatalytic behavior of individual nanoparticles (NPs) by electrochemical amplification method has been reported. For example, the Iridium oxide (IrOx) NP collision on the Pt UME was observed via electrocatalytic water oxidation. However, the bare Pt UME had poor reproducibility for the observation of NP collision signal and required an inconvenient surface pre-treatment for the usage. In this manuscript, we has been investigated other metal electrode such as Cu UME for the reproducible data analysis and convenient use. The IrOx NP collision was successively observed on the bare Cu UME and the reproducibility in collision frequency was improved comparing with previous case using the NaBH4 pre-treated Pt UME. Also, the adhesion coefficient between NP and the Cu UME was studied for better understanding of the single NP collision system.

Observation of Electrocatalytic Amplification of Iridium Oxide (IrO_x) Single Nanoparticle Collision on Copper Ultramicroelectrodes

Choi, Yong Soo,Jung, Seung Yeon,Joo, Jin Woo,Kwon, Seong Jung Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.8

Recently, the observation of the electrocatalytic behavior of individual nanoparticles (NPs) by electrochemical amplification method has been reported. For example, the Iridium oxide ($IrO_x$) NP collision on the Pt UME was observed via electrocatalytic water oxidation. However, the bare Pt UME had poor reproducibility for the observation of NP collision signal and required an inconvenient surface pre-treatment for the usage. In this manuscript, we has been investigated other metal electrode such as Cu UME for the reproducible data analysis and convenient use. The $IrO_x$ NP collision was successively observed on the bare Cu UME and the reproducibility in collision frequency was improved comparing with previous case using the $NaBH_4$ pre-treated Pt UME. Also, the adhesion coefficient between NP and the Cu UME was studied for better understanding of the single NP collision system.

Carbonic anhydrase의 metal 교환을 통한 water oxidation 촉매개발

김민철,이상엽 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

최근 들어 water oxidation 촉매에 대한 연구가 전 세계적으로 활발히 연구되어지고 있다. 그 중에서도 특히 iridium oxide는 촉매 활성 부분에서 가장 좋은 성능을 가진 것으로 알려져 있지만 매장량 문제로 인해 그 가격이 매우 비싸 대체 물질 개발의 필요성이 대두 되고 있다. 따라서 iridium을 이용하여 성능이 좋고 안정성을 가진 새로운 complex를 만드는 연구들이 많이 나오고 있는데 본 연구에서는 iridum과 안정하게 complex를 시키게 하기 위하여 CO₂변환 촉매로 잘 알려진 Carbonic anhydrase(CA)를 이용하였다. CA는 가운데 금속 Zn와 주위에 imidazole로 결합된 구조를 가지고 있는데 이 Zn를 빼내고 ir을 새롭게 결합시킴으로써 water oxidation 촉매를 위한 물질로 새롭게 합성 할 수 있었다. 이렇게 합성된 물질을 사용하여 물에서 산화 되어 발생되는 산소양을 측정할 수 있었고 iron silica particle에 고정화시킴으로써 재사용도 가능함을 실험을 통해 알 수 있었다. 이렇게 천연효소의 우수한 능력인 metal과의 결합력을 water oxidation 연구에 이용함으로써 향후 다양한 연구에도 응용될 수 있음을 기대할 수 있겠다.