• Resources Recycling
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• v.26 no.3
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• pp.26-31
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• 2017

LIX 63 showed a selectivity for the extraction of Pd(II) over other PGMs, such as Pt(IV), Ir(IV) and Rh(III) from 6 M HCl solution. Moreover, HCl solution has significant effect on the oxidation-reduction reaction between Ir(IV) and LIX 63. Therefore, the applicability of employing LIX 63 for the separation of the 4 PGMs was investigated from 3 M HCl solution. From 3 M HCl solution, only Pd(II) was selectively extracted by LIX 63 and its extraction percentage was higher than from 6 M HCl solution. Extraction of the Pd(II) free raffinate with TBP led to the selective extraction of Pt(IV). After oxidation of Ir(III) with $NaClO_3$ to Ir(IV), extraction of the Pt(IV) free raffinate with Aliquat 336 selectively extracted Ir(IV). For each extraction step, optimum stripping conditions were obtained. By this process, it was possible to separate the 4 PGMs by solvent extraction from 3 M HCl solution.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.5
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• pp.26-34
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• 2008

The performance of several catalysts to decompose the high test peroxide (HTP) was described in this paper. Manganese oxide, Platinum and Iridium were coated on the gamma alumina. The catalyst activity as active materials was measured at the flask reactor. The response time of various catalysts was also measured with a 50 Newton class thruster. $Ir/Al_2O_3$ that showed the best activity in the flask reactor and response time at the thruster, failed the reaction when continuous mode test was carried out with the thruster. $Pt/Al_2O_3$ and $MnO_2/Al_2O_3$ can be substitutes to decompose the HTP. In addition, for larger thruster, $MnO_2/Al_2O_3$ can be a good catalyst because its cost is below 5 % of $Pt/Al_2O_3$.

• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.35-39
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• 1995

Simultaneous measurements of trace platinum and rhodium, based on catalytic reduction of protons by the adsorbed Pt-formazone and Rh-formaldehyde complexes formed in formaldehyde-hydrazine-sulfuric acid medium, were demonstrated. The conditions for the measurements of Pt and Rh both present at trace levels (>10-10 M) were 0.004% (w/v) formaldehyde-0.0012% (w/v) hydrazine-0.75 M sulfuric acid. In this medium method detection limits are 7.3${\times}$10-11 M Pt and 3.2${\times}$10-11 M Rh. And dynamic ranges are 5${\times}$10-10~6${\times}$10-8 M and 1${\times}$10-10∼2${\times}$10-8 M for platinum and rhodium respectively. In the linear dynamic ranges, Rh and Ir interfere platinum in the presence of only 10 and 100 times that of Pt respectively. There are no interferences from other platinum group metal ions for rhodium even in the presence of a 500-fold excess of Ir(IV), a hundredfold excess of platinum.

• Resources Recycling
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• v.18 no.4
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• pp.3-13
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• 2009

Rare platinum group (RPG)including rhodium, ruthenium, iridium, osmium, exists at the rate of 0.4 ppb or less in the earth's crust. For the purpose of suggestion to developing necessity for recycling technology with the RPG, survey on the characteristics and the recovery technologies was carried out by using patent information.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.371-374
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• 2008

The performance of several catalysts to decompose the high test peroxide (HTP) was described in this paper. Manganese oxide, Platinum and Iridium were coated on the gamma alumina. The response time of various catalysts was measured with a 50 Newton class thruster. Ir/$Al_2O_3$ that showed the fastest response time at the thruster, failed the reaction when continuous mode test was carried out with the thruster. Pt/$Al_2O_3$ and MnO_2/Al_2O_3$ can be substitutes to decompose the HTP. In addition, for larger thruster, MnO_2/Al_2O_3$ can be a good catalyst because its cost is below 5 % of Pt/$Al_2O_3$.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.12-18
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• 2012

The prohibitively high cost of Pt catalyst might be the biggest barrier for the commercialization of proton exchange membrane fuel cells (PEMFC) of which wide application is expected. Worldwide research efforts for the development of alternative to Pt oxygen reduction reaction (ORR) catalyst are made recently. One of the important considerations in the catalyst development is durability issue as well as economic aspect. From this point of view, platinum group metals (PGM) except Pt can be a candidate for replacing Pt catalyst because the material properties and the catalytic activity of PGM are expected to be similar to Pt. In contrast to Ir, Rh and Os to which not so much attention has been paid as an ORR catalyst, Pd that is most similar to Pt in terms of material properties and catalytic activity and Ru that is in the form of chalcogenide have been studied intensively. Activity comparison between non-Pt and Pt oxygen reduction catalysts by half cell test using RDE (rotating disk electrode) or PEMFC MEA (membrane electrode assembly) operation indicates that Pd-based catalysts show the most similar activity to Pt. In this paper we analyze the composition of PGM ORR catalyst in literature to promote the development of non-Pt ORR catalyst.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.727-734
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• 2017

The electrochemical conversion of $CO_2$ is one of the methods for reducing $CO_2$. Four materials (Ag, Ni, Pt, and Ir) were selected as the electrodes. The electrochemical conversion was performed under a cell voltage of 4.0 V at $600^{\circ}C$. The amounts of $CO_2$ reduction and carbon production were at the highest for Ag, followed by, Pt, Ni, and then Ir. The produced carbon samples were analyzed by thermogravimetric analysis and XRD. The thermogravimetric analysis results indicated that all the carbon produced at each electrode exhibited similar thermal reactivity. The XRD results showed that the crystallization of carbon was different depending on the electrode utilized. Although electrochemical conversion was the highest for the Ag electrode, a loss of material accompanied it. Therefore, for this study, the optimal electrode is Pt, taking into account reactivity and material losses.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.427-428
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• 2014

서론: 최근 전세계적인 고령화 진행에 따른 뇌졸중, 파킨슨병, 알츠하이머병 등과 같은 각종 뇌관련 질환에 대한 관심이 더욱 높아지고 있으며 다양한 뇌질환 치료를 위하여 뇌 신경 신호의 정확한 검출 대한 연구가 학계에서 활발히 진행되고 있다. 효과적인 뇌 신경 신호 검출을 위해서는 세포조직의 손상을 최소화 할 수 있는 초소형 신경탐침 및 극소 면적내에서 극대화된 검출 전극이 구현되어야 한다. 그러나, 극소 면적내에 구성된 소면적 전극을 통한 신호 검출은 전극 계면에서의 높은 임피던스를 야기시켜 정밀한 신경신호 검출에 어려움을 만든다. 따라서, 뇌 신경 신호 검출시 전극 계면에서의 낮은 임피던스를 검출하기 위한 다결정실리콘, 이리듐 산화막, 탄소나노튜브와 같은 다양한 전극 소재를 이용한 신경탐침 연구가 제안되어 왔다. 본 연구에서는 극소화된 전극면적과 신경세포 계면에서의 저 임피던스 신경신호 검출을 위하여 비이온성 계면활성제와 전해도금을 이용하여 높은 거칠기값을 갖는 나노동공 백금층을 검출 전극으로 활용하였다. 실험 결과: 제작된 신경탐침의 몸체는 실리콘으로 이루어지며, 탐침 끝단에는 신호 측정을 위한 나노동공 백금층을 갖는 전극들이 집적되어 있다. Fig. 1 는 제작된 나노동공 백금을 갖는 신경탐침의 이미지 (a), SEM (b), TEM (c), FESEM (d) 측정결과를 보여준다. 0.9 %의 NaCl 용액에서 제작된 신경탐침의 계면임피던스 및 위상각 변화에 대한 측정결과가 Fig. 2에 나타나 있다. 1.2 kHz 주파수에서 $942.6K{\Omega}$ ($0.029{\Omega}cm^2$, $3.14{\mu}m^2$)로 극대화된 실표면적을 갖는 나노동공 백금층에 의하여 매우 낮은 임피던스 특성을 보인 것으로 판단된다. 또한 제작된 신경탐침은 위상각이 $-82.9^{\circ}$로서 캐패시터와 같은 역할을 하고 있다고 예상할 수 있었으며 $4.6mFcm^{-2}$의 축전용량값을 보였다. Fig. 3는 1 M의 황산용액에서 나노동공백금층이 형성된 신경탐침 전극과 형성 전의 전기화학적 표면변화를 비교분석한 결과로서 나노동공 백금층의 형성 전/후의 전류응답 특성이 상이하게 나타났다. 나노동공 백금층의 실표면적 극대화로 인한 전류응답수치 또한 크게 향상 되었으며, 0~-0.25 V 영역에서의 수소 흡착에 따른 환원곡선은 전형적인 백금 특성을 보여주는 결과로 판단 할 수 있다. Table 1는 기존에 연구되었던 신경탐침들과 본 연구에서 제작된 나노동공 백금을 갖는 신경탐침의 임피던스와 캐패시턴스 특성을 비교한 결과이다. 결론: 본 연구에서는 실리콘 신경탐침 끝단에 집적된 전극상에 전해도금법을 이용하여 높은 거칠기값을 갖는 나노동공 백금층을 형성하고 전극 계면상의 낮은 임피던스를 검출을 하였다. 나노동공 백금층을 갖는 신경탐침은 순환전압전류법을 통해 극대화된 실표면적을 극대화를 확인할 수 있었으며, 극대화된 검출 전극면은 저 임피던스 측정에 용이함을 실험을 통해서 증명할 수 있었다. 따라서, 높은 거칠기값의 나노동공 백금층은 초소형화된 신경탐침상에 집적되는 전극면적소형화와 다수의 전극 구현에 효과적일 것으로 판단되며 보다 정확한 신경신호 검출을 통한 뇌질환의 명확한 이해에 유망할 것으로 판단된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.114.1-114.1
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• 2017

불용성 전극이 고속 전기도금 공정에 사용되기 위해서는 전기화학 반응이 우수하고, 높은 내구성을 가져야 한다. 불용성 전극의 내구성은 기지층 표면전처리, 금속산화물 조성, 코팅층 두께, 소결 온도 등 다양한 전극제조 공정인자들에 의해 영향을 받는다. 본 연구에서는 불용성 전극의 내구성을 향상시키기 위해 전극 전처리 및 백금족 산화물 조성비의 공정변수로 전극을 제조하였고, 가속수명평가법을 사용하여 전극의 내구성을 평가하였다. 고속 전기도금 공정환경에서는 이리듐(Ir)계 및 탄탈륨(Ta)계 산화물 조성을 가지는 불용성전극의 내구수명이 우수한 경향을 나타내었으며, 귀금속 산화물 코팅층 두께가 얇을수록 불용성전극의 내구수명은 크게 저하되었다. 또한, Ir-Ta 조성 불용성전극의 경우 내구성 향상 기지체 표면전처리를 통해 전극의 내구수명이 10배 이상 향상되었음을 확인하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.1
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• pp.23-31
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• 2004

For the fabrication of high efficient bifunctional electrocatalyst of oxygen electrode for PEM URFC (Polymer Electrolyte Membrane Unitized Regenerative Fuel Cell), which is a promising energy storage and conversion system using hydrogen as the energy medium, several bifunctional electrocatalysts were prepared and tested in a single cell URFC system. The catalysts for oxygen electrode revealed fuel cell performance in the order of Pt black > PtIr > PtRuOx > PtRu ~ PtRuIr > PtIrOx, whereas water electrolysis performance in the order of PtIr ~ PtIrOx > PtRu > PtRuIr > PtRuOx ~ Pt black. Considering both reaction modes PtIr was the most effective elctrocatalyst for oxygen electrode of present PEM URFC system. In addition, the water electrolysis performance was significantly improved when Ir or IrOx was added to Pt black just 1 wt.% without the decrease of fuel cell performance. Based on the catalyst screening and the optimization of catalyst composition and loading, the optimum catalyst electrodes for PEM URFC were $1.0mg/cm^2$ of Pt black as hydrogen electrode and $2.0mg/cm^2$ of PtIr (99:1) as oxygen electrode.