Determination of the Langmuir and Temkin Adsorption Isotherms of H for the Cathodic H₂ Evolution Reaction at a Pt/KOH Solution Interface Using the Phase-Shift Method

Chun Jang-H.,Jeon Sang-K.,Chun Jin-Y. The Korean Electrochemical Society 2006 한국전기화학회지 Vol.9 No.1

The phase-shift method for determining the Langmuir, Frumkin, and Temkin adsorption isotherms ($\theta_H\;vs.\;E$) of H for the cathodic $H_2$ evolution reaction (HER) at a Pt/0.1 M KOH solution interface has been proposed and verified using cyclic voltammetric, differential pulse voltammetric, and electrochemical impedance techniques. At the Pt/0.1 M KOH solution interface, the Langmuir and Temkin adsorption isotherms ($\theta_H\;vs.\;E$), the equilibrium constants ($K_H=2.9X10^{-4}mol^{-1}$ for the Langmuir and $K_H=2.9X10^{-3}\exp(-4.6\theta_H)mol^{-1}$ for the Temkin adsorption isotherm), the interaction parameters (g=0 far the Langmuir and g=4.6 for the Temkin adsorption isotherm), the rate of change of the standard free energy of $\theta_H\;with\;\theta_H$ (r=11.4 kJ $mol^{-1}$ for g=4.6), and the standard free energies (${\Delta}G_{ads}^{\circ}=20.2kJ\;mol^{-1}$ for $k_H=2.9\times10^{-4}mol^{-1}$, i.e., the Langmuir adsorption isotherm, and $16.7<{\Delta}G_\theta^{\circ}<23.6kJ\;mol^{-1}$ for $K_H=2.9\times10^{-3}\exp(-4.6\theta_H)mol^{-1}$ and $0.2<\theta_H<0.8$, i.e., the Temkin adsorption isotherm) of H for the cathodic HER are determined using the phase-shift method. At intermediate values of $\theta_H$, i.e., $0.2<\theta_H<0.8$, the Temkin adsorption isotherm ($\theta_H\;vs.\;E$) corresponding to the Langmuir adsorption isotherm ($\theta_H\;vs.\;E$), and vice versa, is readily determined using the constant conversion factors. The phase-shift method and constant conversion factors are useful and effective for determining the Langmuir, Frumkin, and Temkin adsorption isotherms of intermediates for sequential reactions and related electrode kinetic and thermodynamic data at electrode catalyst interfaces.

Analysis on the Langmuir Adsorption Isotherm of the Over-Potentially Deposited Hydrogen (OPD H) at the Polycrystalline Au|Acidic Aqueous Electrolyte Interface Using the Phase-Shift Method

Chun Jang H.,Jeon Sang K. The Korean Electrochemical Society 2001 한국전기화학회지 Vol.4 No.3

순환전압전류 및 교류임피던스 기법을 이용하여 다결정 $0.5M\;H_2SO_4$수용액 계면에서 음극 $H_2$발생 반응을 위한 과전위 전착(흡착)된 수소의 Langmuir흡착등온식을 연구조사 하였다. 다결정 $Au|0.5M\;H_2SO_4$수용액 계면에서, 최적중간주파수일 때 위상이동 $(0^{\circ}\leq{-\phi}\leq90^{\circ})$ 거동은 표면피복율$(1\geq{\theta}\geq0)$ 거동에 정확하게 상응한다. 최적중간주 파수일 때 위상이동 변화 $({-\phi}\;vs.\;E)$즉 위상이동 방법은 다결정 $Au|0.5M\;H_2SO_4$수용액 계면에서 음극 $H_2$발생 반응을 위한 과전위 전착(흡착)된 수소의 Langmuir 흡착등온식$(\theta\;vs.\;E)$을 추정할 수 있는 새로운 방법으로 사용될 수 있다. 다결정 $Au|0.5M\;H_2SO_4$ 수용액 계면에서, 과전위 전착(흡착)된 수소의 흡착평형상수(K)와 표준자유에너지 $({\Delta}G_{ads})$는 각각 $2.3\times10^{-6}$과 $32.2kJ\;mol^{-1}$이다. The Langmuir adsorption isotherm of the over-potentially deposited hydrogen (OPD H) for the cathodic $H_2$ evolution reaction (HER) at the $poly-Au|0.5M\;H_2SO_4$ aqueous electrolyte interface has been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift $(0^{\circ}\leq{-\phi}\leq90^{\circ})$ for the optimum intermediate frequency corresponds well to that of the fractional surface coverage $(1\geq{\theta}\geq0)$ at the interface. The phase-shift profile $({-\phi}\;vs.\;E)$ for the optimum intermediate frequency, i.e., the phase-shift method, can be used as a new method to estimate the Langmuir adsorption isotherm $(\theta\;vs.\;E)$ of the OPD H for the cathodic HER at the interface. At the poly-$Au|0.5M\;H_2SO_4$ electrolyte interface, the equilibrium constant (K) and standard free energy $({\Delta}G_{ads})$ of the OPD H are $2.3\times10^{-6}\;and\;32.2\;kJ\;mol^{-1}$, respectively.

Constant Correlation Factors between Temkin and Langmuir or Frumkin Adsorption Isotherms at Poly-Pt, Re, and Ni/Aqueous Electrolyte Interfaces

Chun Jang H.,Jeon Sang K.,Chun Jin Y. The Korean Electrochemical Society 2004 한국전기화학회지 Vol.7 No.4

The constant correlation factors between the Temkin and the Langmuir or the Frumkin adsorption isotherms of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER) at poly-Pt and Re/0.5M $H_2SO_4$ and poly-Ni/0.05 M KOH aqueous electrolyte interfaces have been experimentally and consistently found using the phase-shift method. At intermediate values of the fractional surface coverage $(\theta),\;i.e.,\;02<{\theta}<0.8$, the Langmuir and Temkin adsorption isotherms of OPD H for the cathodic HER are correlated to each other even though the adsorption conditions or processes are different from each other. At the same range of $\theta$, correspondingly, the Frumkin and Temkin adsorption isotherms of OPD H for the cathodic HER are correlated to each other. The equilibrium constants $(K_o)$ for the Temkin adsorption isotherms $({\theta}\;vs.\; E)$ are consistently ca. 10 times greater than those (K, Ko) for the corresponding Langmuir or Frumkin adsorption isotherms ($({\theta}\;vs.\; E)$. The interaction parameters (g) for the Temkin adsorption isotherms $({\theta}\;vs.\; E)$ are consistently ra. 4.6 greater than those (g) for the corresponding Langmuir or Frumkin adsorption isotherms $({\theta}\;vs.\; E)$. These numbers (10 times and 4.6) can be taken as constant correlation factors between the corresponding adsolftion isotherms (Temkin, Langmuir, Frumkin) at the interfaces. The Temkin adsorption isotherm corresponding to the Langmuir or the Frumkin adsorption isotherm, and vice versa, can be effectively verified or confirmed using the constant correlation factors. Both the phase-shift methodand constant correlation factors are useful and effective for determining or confirming the suitable adsorption isotherms (Temkin, Langmuir, Frumkin) of intermediates for sequential reactions in electrochemical systems.

The Phase-Shift Method for the Langmuir Adsorption Isotherms at the Noble Metal (Au, Rh) Electrode Interfaces

천장호,전상규,이재항,Chun, Jang H.,Jeon, Sang K.,Lee, Jae H. The Korean Electrochemical Society 2003 한국전기화학회지 Vol.6 No.2

The Langmuir adsorption isotherms of the over-potentially deposited hydrogen (OPD H) fur the cathodic $H_2$ evolution reaction (HER) at the poly-Au and $Rh|0.5M\;H_2SO_4$ aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift $(0^{\circ}{\leq}{-\phi}{\leq}90^{\circ})$ for the optimum intermediate frequency corresponds well to that of the fractional surface coverage $(1{\geq}{\theta}{\geq}0)$ at the interfaces. The phase-shift profile $({-\phi}\;vs.\;E)$ for the optimum intermediate frequency, i.e., the phase-shift method, can be used as a new electrochemical method to determine the Langmuir adsorption isotherm $({\theta}\;vs.\;E)$ of the OPD H for the cathodic HER at the interfaces. At the poly-Au|0.5M $H_2SO_4$ aqueous electrolyte interface, the equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the OPD H are $2.3\times10^{-6}$ and 32.2kJ/mol, respectively. At the poly-Rh|0.5M $H_2SO_4$ aqueous electrolyte interface, K and ${\Delta}G_{ads}$ of the OPD H are $4.1\times10^4\;or\;1.2\times10^{-2}$ and 19.3 or 11.0kJ/mol depending on E, respectively. In contrast to the poly-Au electrode interface, the two different Langmuir adsorption isotherms of the OPD H are observed at the poly-Rh electrode interface. The two different Langmuir adsorption isotherms of the OPD H correspond to the two different adsorption sites of the OPD H on the poly-Rh electrode surface.

The Phase-Shift Method for the Langmuir Adsorption Isotherms of Electroadsorbed Hydrogens for the Cathodic H₂ Evolution Reactions at the Poly-Pt Electrode Interfaces

천장호,전상규,이재항,Chun, Jang H.,Jeon, Sang K.,Lee, Jae H. The Korean Electrochemical Society 2002 한국전기화학회지 Vol.5 No.3

순환전압전류 및 교류임피던스 기법을 이용하여 다결정 Pt/0.5M $H_2SO_4$ 및 0.5M LiOH수용액 계면에서 저전위 수소흡착(UPD H) 과 전위 수소흡착(OPD H)에 관한 Langmuir 흡착등온식 $({\theta}\;vs.\;E)$ 을 연구조사 하였다. 계면에서 치적중간주파수일 때 위상이동$(0^{\circ}{\leq}{-\phi}{\leq}90^{\circ})$ 거동은 표면피복율$(1{\geq}{\theta}{\geq}0)$ 거동에 정확하게 상응한다. 위상이 동 방법 즉 최적중간주파수일 때 위상이동 변화$({-\phi}\;vs.\;E)$는 계면에서 음극 $H_2$ 발생 반응에 관한 UPD H와 OPDH의 Langmuir흡착등온식을 결정할 수 있는 새로운 전기화학적 방법으로 사용할 수 있다 다결정 Pt/0.5M $H_2SO_4$ 수용액 계면에서 OPD H의 흡착평형상수(K)와 표준자유에너지$({\Delta}G_{ads})$는 각각 $2.1\times10^{-4}$와 21.0kJ/mol 이다. 다결정 Pt/0.5M LiOH 수용액 계면에서 K는 음전위(E)에 따라 2.7 (UPD H)에서 $6.2\times10^{-6}$ (OPD H) 또는 $6.2\times10^{-6}$(OPD H)에서 2.7 (UPD H)로 전이한다. 유사하게 ${\Delta}G_{ads}$는 E에 따라 -2.5kJ/mol (UPD H)에서 29.7kJ/mol (OPD H)또는 29.7kJ/mol (OPD H)에서 -2.5kJ/mol (UPD H)로 전이한다. K와 ${\Delta}G_{ads}$의 전이는 다결정 Pt전극 표면의 상이한 UPD H와 OPD H의 흡착부위에 기인한다. 다결정 Pt전극 계면에서 UPD H와 OPD H는 음극 $H_2$ 발생 반응에 따른 순차적 과정이 아니라, 수소 흡착부위 자체에 따른 독립적 과정이다. UPD H와 OPD H의 기준은 음극 $H_2$발생 반응과 전위가 아니라, 수소 흡착부위와 과정이다. 수용액에서 음극 $H_2$발생 반응에는 다결정 Pt선 전극이 단결정 Pt(100)원반 전극보다 더 효율적이고 유용하다 위상이동 방법은 열역학적 방법과 상충적이 아니라, 보완적이다. The Langmuir adsorption isotherms of the under-potentially deposited hydrogen (UPD H) and the over-potentially deposited hydrogen (OPD H) at the poly-Pt/0.5M $H_2SO_4$ and 0.5 M LiOH aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift $(0^{\circ}{\leq}{-\phi}{\leq}90^{\circ})$ for the optimum intermediate frequency corresponds well to that of the fractional surface coverage $(1{\geq}{\theta}{\geq}0)$ at the interfaces. The phase-shift method, i.e., the phase-shift profile $({-\phi}\;vs.\;E)$ for the optimum intermediate frequency, can be used as a new electrochemical method to determine the Langmuir adsorption isotherms $({\theta}\;vs.\;E)$ of the UPD H and the OPD H for the cathodic $H_2$ evolution reactions at the interfaces. At the poly-Pt/0.5M $H_2SO_4$ aqueous electrolyte interface, the equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the OPD H are $2.1\times10^{-4}$ and 21.0kJ/mol, respectively. At the poly-Pt/0.5M LiOH aqueous electrolyte interface, K transits from 2.7(UPD H) to $6.2\times10^{-6}$ (OPD H) depending on the cathode potential (E) and vice versa. Similarly, ${\Delta}G_{ads}$ transits from -2.5kJ/mol (UPD H) to 29.7kJ/mol (OPD H) depending on I and vice versa. The transition of K and ${\Delta}G_{ads}$ is attributed to the two distinct adsorption sites of the UPD H and the OPD H on the poly-Pt surface. The UPD H and the OPD H on the poly-Pt surface are the independent processes depending on the H adsorption sites themselves rather than the sequential processes for the cathodic $H_2$ evolution reactions. The criterion of the UPD H and the OPD H is the H adsorption sites and processes rather than the $H_2$ evolution reactions and potentials. The poly-Pt wire electrode is more efficient and useful than the Pt(100) disc electrode for the cathodic $H_2$ evolution reactions in the aqueous electrolytes. The phase-shift method is well complementary to the thermodynamic method rather than conflicting.

Review on the Determination of Frumkin, Langmuir, and Temkin Adsorption Isotherms at Electrode/Solution Interfaces Using the Phase-Shift Method and Correlation Constants

( Jinyoung Chun ),( Jang H. Chun ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.6

This review article described the electrochemical Frumkin, Langmuir, and Temkin adsorption isotherms of over-potentially deposited hydrogen (OPD H) and deuterium (OPD D) for the cathodic H₂ and D₂ evolution reactions (HER, DER) at Pt, Ir, Pt-Ir alloy, Pd, Au, and Re/normal (H₂O) and heavy water (D₂O) solution interfaces. The Frum-kin, Langmuir, and Temkin adsorption isotherms of intermediates (OPD H, OPD D, etc.) for sequential reactions (HER, DER, etc.) at electrode/solution interfaces are determined using the phase-shift method and correlation constants, which have been suggested and developed by Chun et al. The basic procedure of the phase-shift method, the Frumkin, Lang-muir, and Temkin adsorption isotherms of OPD H and OPD D and related electrode kinetic and thermodynamic param-eters, i.e., the fractional surface coverage (0 ≤ θ ≤ 1) vs. potential (E) behavior (θ vs. E), equilibrium constant (K), interaction parameter (g), standard Gibbs energy (ΔG_θ˚) of adsorption, and rate (r) of change of ΔG_θ˚ with θ (0 ≤ θ ≤ 1), at the interfaces are briefly interpreted and summarized. The phase-shift method and correlation constants are useful and effective techniques to determine the Frumkin, Langmuir, and Temkin adsorption isotherms and related electrode kinetic and thermodynamic parameters (θ vs. E, K, g, ΔG_θ˚, r) at electrode/solution interfaces.

Horizontal divergence of typhoon-generated gravity waves in the upper troposphere and lower stratosphere (UTLS) and its influence on typhoon evolution

Kim, S. H.,Chun, H.-Y.,Jang, W. Copernicus GmbH 2014 Atmospheric chemistry and physics Vol.14 No.7

<P>Abstract. The characteristics of horizontal divergence induced by typhoon-generated gravity waves (HDTGWs) and the influence of HDTGW on typhoon evolution are investigated based on the simulation results of Typhoon Saomai (2006) using the Weather Research and Forecasting (WRF) model. The power spectral density of HDTGW shows dominant powers at horizontal wavelengths of 20-30 km and at periods of less than 1 h. This is associated with gravity waves generated by vigorous convective clouds in an inner core region of the typhoon. However, the domain-averaged HDTGW in the upper troposphere and lower stratosphere had a spectral peak at 24 h, which is well correlated with the minimum sea-level pressure of the typhoon, especially during a rapidly developing period. The 24 h period of the averaged HDTGW stems from the inertia-gravity waves generated by the convective clouds in the spiral rainbands, and showed no clear association with the thermal tides or the diurnal variation of precipitation. </P>

암모니아와 물이 함유된 조건에서 V2O5 / SiO2 촉매에 의한 황화수소의 선택적 제거

정종식,우희철,박대원,천승우,장재열,김효선 한국공업화학회 1997 응용화학 Vol.1 No.2

V₂O_5/SiO₂ catalysts showed good activity in the selective removal of H₂S in the presence of ammonia and water. H₂S in ammonia and water vapor can be recovered as harmless solid products (elemental sulfur and various ammonium sulfates) without considerable SO₂ emission. Distribution of sulfur and salts were varied with types of catalyst and compositions of reactant.

의료전달체계 시행후 3차 의료기관 응급실 내원 환자에 대한 실태조사

이명춘,조종환,김현철,장민옥,박혜숙,조홍준,김영식 대한가정의학회 1990 Korean Journal of Family Medicine Vol.11 No.6

Determination of Adsorption Isotherms of Hydrogen on Zirconium in Sulfuric Acid Solution Using the Phase-Shift Method and Correlation Constants

Chun, Jang-H.,Chun, Jin-Y. The Korean Electrochemical Society 2009 한국전기화학회지 Vol.12 No.1

The phase-shift method and correlation constants, i.e., the unique electrochemical impedance spectroscopy (EIS) techniques for studying the linear relationship between the behavior ($-{\varphi}$ vs. E) of the phase shift ($90^{\circ}{\geq}-{\varphi}{\geq}0^{\circ}$) for the optimum intermediate frequency and that ($\theta$ vs. E) of the fractional surface coverage ($0{\leq}{\theta}{\leq}1$), have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at noble metal (alloy)/aqueous solution interfaces. At a Zr/0.2 M ${H_2}{SO_4}$ aqueous solution interface, the Frumkin and Temkin adsorption isotherms ($\theta$ vs. E), equilibrium constants (K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ for the Frumkin and K = $1.401{\times}10^{-16}\exp(8.1{\theta})mol^{-1}$ for the Temkin adsorption isotherm), interaction parameters (g = 3.5 for the Frumkin and g = 8.1 for the Temkin adsorption isotherm), rates of change of the standard free energy (r = $8.7\;kJ\;mol^{-1}$ for g = 3.5 and r = $20\;kJ\;mol^{-1}$ for g = 8.1) of H with $\theta$, and standard free energies ($96.13{\leq}{\Delta}G^0_{\theta}{\leq}104.8\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ and $0{\leq}{\theta}{\leq}1$ and ($94.44<{\Delta}G^0_{\theta}<106.5\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-16}\exp(-8.1{\theta})mol^{-1}$ and $0.2<{\theta}<0.8$) of H are determined using the phase-shift method and correlation constants. At 0.2 < $\theta$ < 0.8, the Temkin adsorption isotherm correlating with the Frumkin adsorption isotherm, and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are probably the most accurate, useful, and effective ways to determine the adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at highly corrosion-resistant metal/aqueous solution interfaces.