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Jang H Chun - One of the best experts on this subject based on the ideXlab platform.
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the phase shift method for determining Langmuir and temkin Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at the poly pt h2so4 aqueous electrolyte interface
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Nam Y Kim, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior ( - ϕ vs. E ) of the phase shift ( 0 ∘ ⩽ - ϕ ⩽ 90 ∘ ) for the optimum intermediate frequency and that ( θ vs. E ) of the fractional surface coverage ( 1 ⩾ θ ⩾ 0 ) of over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER), i.e., the phase-shift method, at the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface has been verified using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The phase-shift method for determining the suitable Adsorption isotherm (Langmuir, Frumkin, Temkin) of OPD H for the cathodic HER at the interface also has been proposed. At the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( K = 1.3 × 10 - 4 ) for OPD H and the standard free energy ( Δ G ads 0 = 22.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the same interface, the Temkin Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( 1.3 × 10 - 3 ⩾ K ⩾ 1.3 × 10 - 5 with θ , i.e., 0 ⩽ θ ⩽ 1 ) for OPD H, and the standard free energy ( 16.5 ⩽ Δ G θ 0 ⩽ 27.9 kJ / mol with θ , i.e., 0 ⩽ θ ⩽ 1 ) of OPD H are also determined using the phase-shift method. At the intermediate values of θ , i.e., 0.2 θ 0.8 , the Langmuir and Temkin Adsorption isotherms of OPD H for the cathodic HER at the interface are converted to each other. The equilibrium constant ( K 0 ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 10 times greater than that ( K ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). The interaction parameter ( g ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 4.6 greater than that ( g ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). These numbers (10 times and 4.6) can be taken as constant conversion factors between the corresponding Adsorption isotherms (Temkin, Langmuir, Frumkin). The Temkin Adsorption isotherm corresponding to the Langmuir or the Frumkin Adsorption isotherm, and vice versa, can be effectively converted using the constant conversion factors. Both the phase-shift method and constant conversion factors can be effectively used as a new electrochemical method to determine the suitable Adsorption isotherms (Langmuir, Frumkin, Temkin) of H for the cathodic HER in electrochemical systems.
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the phase shift method for determining Langmuir Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at poly re aqueous electrolyte interfaces
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior (−ϕ vs. E) of the phase shift (0°⩽−ϕ⩽90°) for the optimum intermediate frequency and that (θ vs. E) of the fractional surface coverage (1⩾θ⩾0) of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER), i.e., the phase-shift method, at poly-Re/ 0.5 M H 2 SO 4 and 0.1 M KOH aqueous electrolyte interfaces has been suggested and verified using cyclic voltammetric, differential pulse voltammetric, and AC impedance techniques. At the poly-Re/ 0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm (θ vs. E) of OPD H, the equilibrium constant (K=4.5×10−7) for OPD H, and the standard free energy ( Δ G ads o =36.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the poly-Re/ 0.1 M KOH aqueous electrolyte interface, θ vs. E of OPD H, K=1.9×10−6 for OPD H, and Δ G ads o =32.6 kJ / mol of OPD H are also determined using the phase-shift method. The applicability of the Frumkin and Temkin Adsorption isotherms (θ vs. E) of OPD H for the cathodic HER at the interfaces also has been studied using the phase-shift method. The phase-shift method experimentally provides the link between the microscopic system of the Adsorption sites and process of OPD H on the atoms and the macroscopic system of the electrode kinetics and thermodynamics for OPD H at the interfaces. The phase-shift method can be effectively used as a new electrochemical method to determine or estimate Adsorption isotherms of intermediates for sequential reactions in electrochemical systems.
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determination of the Langmuir Adsorption isotherms of under and over potentially deposited hydrogen for the cathodic h2 evolution reaction at poly ir aqueous electrolyte interfaces using the phase shift method
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Sang K Jeon, Bok Ki Kim, Jin Y ChunAbstract:Abstract The Langmuir Adsorption isotherms of under-potentially deposited hydrogen (UPD H) and over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER) at poly-Ir /0.5 M H2SO4 and 0.05 M KOH aqueous electrolyte interfaces have been studied using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The behavior of the lagged phase shift (0°⩽−φ⩽90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1⩾θ⩾0) of H (UPD H, OPD H) for the cathodic HER at the interfaces. A linear relationship between the phase-shift profile (−φ vs. E) for the optimum intermediate frequency and the Langmuir Adsorption isotherm (θ vs. E) of H (UPD H, OPD H), i.e., the phase-shift method, can be used as a new electrochemical method to determine or estimate the fractional surface coverage (θ), equilibrium constant (K), and standard free energy (ΔGads0) of H (UPD H, OPD H) for the cathodic HER at the interfaces. At the poly-Ir /0.5 M H2SO4 aqueous electrolyte interface, K and ΔGads0 of the OPD H for the cathodic HER are 9.9×10−5 and 22.8 kJ/mol , respectively. At the poly-Ir /0.05 M KOH aqueous electrolyte interface, K and ΔGads0 of the UPD H for the cathodic HER are 3.9 and −3.4 kJ/mol , respectively. At the poly-Ir /0.05 M KOH aqueous electrolyte interface, K and ΔGads0 of the OPD H for the cathodic HER are 5.8×10−4 and 18.5 kJ/mol , respectively. The two different Langmuir Adsorption isotherms for H (UPD H, OPD H) correspond to two different Adsorption sites of H (UPD H, OPD H) on the poly-Ir electrode surface. The two different Adsorption sites of UPD H and OPD H act as two distinguishable electroadsorbed H species. The phase-shift method is a simple and efficient tool for determining the Adsorption, electrode kinetic, and thermodynamic parameters (θ, K, ΔGads0) of H (UPD H, OPD H) for the cathodic HER at the interfaces.
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determination of the equilibrium constant and standard free energy of the over potentially deposited hydrogen for the cathodic h2 evolution reaction at the pt rh alloy electrode interface using the phase shift method
International Journal of Hydrogen Energy, 2003Co-Authors: Jang H Chun, Sang K JeonAbstract:Abstract The Langmuir Adsorption isotherm of the over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER) at the Pt–Rh (Pt:Rh; 80: 20 wt % ) alloy /0.5 M H 2 SO 4 aqueous electrolyte interface has been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift (0°⩽− φ ⩽90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1⩾ θ ⩾0) of the OPD H for the cathodic HER at the interface. The phase-shift profile (− φ 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 ( θ vs. E ) of the OPD H for the cathodic HER at the interface. At the Pt–Rh alloy electrode interface, the equilibrium constant ( K ) and the standard free energy (Δ G ads ) of the OPD H are 2.2×10 −4 and 20.9 kJ / mol , respectively. At the steady state, the behaviors of the cyclic voltammogram and the Langmuir Adsorption isotherm of the OPD H for the cathodic HER at the Pt–Rh alloy electrode interface are similar to those of the pure Pt electrode interfaces. At the steady state, the effect of Rh on the OPD H for the cathodic HER can be neglected at the Pt–Rh (Pt:Rh; 80: 20 wt % ) alloy /0.5 M H 2 SO 4 aqueous electrolyte interface.
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Langmuir Adsorption isotherms of overpotentially deposited hydrogen at poly au and rh h 2 so 4 aqueous electrolyte interfaces qualitative analysis using the phase shift method
Journal of The Electrochemical Society, 2003Co-Authors: Jang H Chun, Nam Y KimAbstract:The Langmuir Adsorption isotherms of over-potentially deposited hydrogen (OPD H) for the cathodic hydrogen evolution reaction (HER) at poly-Au and Rh/0.5 M H 2 SO 4 aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift (0° ≤ -Φ ≤ 90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1 ≥ θ ≥ 0) of OPD H for the cathodic HER at the interfaces. The phase-shift profile (-Φ 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 (θ as E) of the OPD H for the cathodic HER at the interfaces. At the poly-Au/(0.5 M H 2 SO 4 aqueous electrolyte interface, the equilibrium constant (K) and the standard free energy (ΔG ads )of the OPD H are 2.3 X 10 -6 and 32.2 kJ/mol, respectively. At the poly-Rh/0.5 M H 2 SO 4 aqueous electrolyte interface, K and ΔG ads, of the OPD H are 4.1 x 10 -4 or 1.2 X 10 -2 and 19.3 or 11.0 kJ/mol depending on E, respectively. In contrast to the poly-Au electrode interface, two different Langmuir Adsorption isotherms of OPD H are observed at the poly-Rh electrode interface. The two different Langmuir Adsorption isotherms of OPD H correspond to two different Adsorption sites of OPD H on the poly-Rh electrode surface.
Jin Y Chun - One of the best experts on this subject based on the ideXlab platform.
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the phase shift method for determining Langmuir and temkin Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at the poly pt h2so4 aqueous electrolyte interface
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Nam Y Kim, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior ( - ϕ vs. E ) of the phase shift ( 0 ∘ ⩽ - ϕ ⩽ 90 ∘ ) for the optimum intermediate frequency and that ( θ vs. E ) of the fractional surface coverage ( 1 ⩾ θ ⩾ 0 ) of over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER), i.e., the phase-shift method, at the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface has been verified using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The phase-shift method for determining the suitable Adsorption isotherm (Langmuir, Frumkin, Temkin) of OPD H for the cathodic HER at the interface also has been proposed. At the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( K = 1.3 × 10 - 4 ) for OPD H and the standard free energy ( Δ G ads 0 = 22.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the same interface, the Temkin Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( 1.3 × 10 - 3 ⩾ K ⩾ 1.3 × 10 - 5 with θ , i.e., 0 ⩽ θ ⩽ 1 ) for OPD H, and the standard free energy ( 16.5 ⩽ Δ G θ 0 ⩽ 27.9 kJ / mol with θ , i.e., 0 ⩽ θ ⩽ 1 ) of OPD H are also determined using the phase-shift method. At the intermediate values of θ , i.e., 0.2 θ 0.8 , the Langmuir and Temkin Adsorption isotherms of OPD H for the cathodic HER at the interface are converted to each other. The equilibrium constant ( K 0 ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 10 times greater than that ( K ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). The interaction parameter ( g ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 4.6 greater than that ( g ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). These numbers (10 times and 4.6) can be taken as constant conversion factors between the corresponding Adsorption isotherms (Temkin, Langmuir, Frumkin). The Temkin Adsorption isotherm corresponding to the Langmuir or the Frumkin Adsorption isotherm, and vice versa, can be effectively converted using the constant conversion factors. Both the phase-shift method and constant conversion factors can be effectively used as a new electrochemical method to determine the suitable Adsorption isotherms (Langmuir, Frumkin, Temkin) of H for the cathodic HER in electrochemical systems.
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the phase shift method for determining Langmuir Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at poly re aqueous electrolyte interfaces
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior (−ϕ vs. E) of the phase shift (0°⩽−ϕ⩽90°) for the optimum intermediate frequency and that (θ vs. E) of the fractional surface coverage (1⩾θ⩾0) of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER), i.e., the phase-shift method, at poly-Re/ 0.5 M H 2 SO 4 and 0.1 M KOH aqueous electrolyte interfaces has been suggested and verified using cyclic voltammetric, differential pulse voltammetric, and AC impedance techniques. At the poly-Re/ 0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm (θ vs. E) of OPD H, the equilibrium constant (K=4.5×10−7) for OPD H, and the standard free energy ( Δ G ads o =36.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the poly-Re/ 0.1 M KOH aqueous electrolyte interface, θ vs. E of OPD H, K=1.9×10−6 for OPD H, and Δ G ads o =32.6 kJ / mol of OPD H are also determined using the phase-shift method. The applicability of the Frumkin and Temkin Adsorption isotherms (θ vs. E) of OPD H for the cathodic HER at the interfaces also has been studied using the phase-shift method. The phase-shift method experimentally provides the link between the microscopic system of the Adsorption sites and process of OPD H on the atoms and the macroscopic system of the electrode kinetics and thermodynamics for OPD H at the interfaces. The phase-shift method can be effectively used as a new electrochemical method to determine or estimate Adsorption isotherms of intermediates for sequential reactions in electrochemical systems.
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determination of the Langmuir Adsorption isotherms of under and over potentially deposited hydrogen for the cathodic h2 evolution reaction at poly ir aqueous electrolyte interfaces using the phase shift method
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Sang K Jeon, Bok Ki Kim, Jin Y ChunAbstract:Abstract The Langmuir Adsorption isotherms of under-potentially deposited hydrogen (UPD H) and over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER) at poly-Ir /0.5 M H2SO4 and 0.05 M KOH aqueous electrolyte interfaces have been studied using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The behavior of the lagged phase shift (0°⩽−φ⩽90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1⩾θ⩾0) of H (UPD H, OPD H) for the cathodic HER at the interfaces. A linear relationship between the phase-shift profile (−φ vs. E) for the optimum intermediate frequency and the Langmuir Adsorption isotherm (θ vs. E) of H (UPD H, OPD H), i.e., the phase-shift method, can be used as a new electrochemical method to determine or estimate the fractional surface coverage (θ), equilibrium constant (K), and standard free energy (ΔGads0) of H (UPD H, OPD H) for the cathodic HER at the interfaces. At the poly-Ir /0.5 M H2SO4 aqueous electrolyte interface, K and ΔGads0 of the OPD H for the cathodic HER are 9.9×10−5 and 22.8 kJ/mol , respectively. At the poly-Ir /0.05 M KOH aqueous electrolyte interface, K and ΔGads0 of the UPD H for the cathodic HER are 3.9 and −3.4 kJ/mol , respectively. At the poly-Ir /0.05 M KOH aqueous electrolyte interface, K and ΔGads0 of the OPD H for the cathodic HER are 5.8×10−4 and 18.5 kJ/mol , respectively. The two different Langmuir Adsorption isotherms for H (UPD H, OPD H) correspond to two different Adsorption sites of H (UPD H, OPD H) on the poly-Ir electrode surface. The two different Adsorption sites of UPD H and OPD H act as two distinguishable electroadsorbed H species. The phase-shift method is a simple and efficient tool for determining the Adsorption, electrode kinetic, and thermodynamic parameters (θ, K, ΔGads0) of H (UPD H, OPD H) for the cathodic HER at the interfaces.
Sang K Jeon - One of the best experts on this subject based on the ideXlab platform.
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the phase shift method for determining Langmuir and temkin Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at the poly pt h2so4 aqueous electrolyte interface
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Nam Y Kim, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior ( - ϕ vs. E ) of the phase shift ( 0 ∘ ⩽ - ϕ ⩽ 90 ∘ ) for the optimum intermediate frequency and that ( θ vs. E ) of the fractional surface coverage ( 1 ⩾ θ ⩾ 0 ) of over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER), i.e., the phase-shift method, at the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface has been verified using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The phase-shift method for determining the suitable Adsorption isotherm (Langmuir, Frumkin, Temkin) of OPD H for the cathodic HER at the interface also has been proposed. At the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( K = 1.3 × 10 - 4 ) for OPD H and the standard free energy ( Δ G ads 0 = 22.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the same interface, the Temkin Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( 1.3 × 10 - 3 ⩾ K ⩾ 1.3 × 10 - 5 with θ , i.e., 0 ⩽ θ ⩽ 1 ) for OPD H, and the standard free energy ( 16.5 ⩽ Δ G θ 0 ⩽ 27.9 kJ / mol with θ , i.e., 0 ⩽ θ ⩽ 1 ) of OPD H are also determined using the phase-shift method. At the intermediate values of θ , i.e., 0.2 θ 0.8 , the Langmuir and Temkin Adsorption isotherms of OPD H for the cathodic HER at the interface are converted to each other. The equilibrium constant ( K 0 ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 10 times greater than that ( K ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). The interaction parameter ( g ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 4.6 greater than that ( g ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). These numbers (10 times and 4.6) can be taken as constant conversion factors between the corresponding Adsorption isotherms (Temkin, Langmuir, Frumkin). The Temkin Adsorption isotherm corresponding to the Langmuir or the Frumkin Adsorption isotherm, and vice versa, can be effectively converted using the constant conversion factors. Both the phase-shift method and constant conversion factors can be effectively used as a new electrochemical method to determine the suitable Adsorption isotherms (Langmuir, Frumkin, Temkin) of H for the cathodic HER in electrochemical systems.
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the phase shift method for determining Langmuir Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at poly re aqueous electrolyte interfaces
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior (−ϕ vs. E) of the phase shift (0°⩽−ϕ⩽90°) for the optimum intermediate frequency and that (θ vs. E) of the fractional surface coverage (1⩾θ⩾0) of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER), i.e., the phase-shift method, at poly-Re/ 0.5 M H 2 SO 4 and 0.1 M KOH aqueous electrolyte interfaces has been suggested and verified using cyclic voltammetric, differential pulse voltammetric, and AC impedance techniques. At the poly-Re/ 0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm (θ vs. E) of OPD H, the equilibrium constant (K=4.5×10−7) for OPD H, and the standard free energy ( Δ G ads o =36.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the poly-Re/ 0.1 M KOH aqueous electrolyte interface, θ vs. E of OPD H, K=1.9×10−6 for OPD H, and Δ G ads o =32.6 kJ / mol of OPD H are also determined using the phase-shift method. The applicability of the Frumkin and Temkin Adsorption isotherms (θ vs. E) of OPD H for the cathodic HER at the interfaces also has been studied using the phase-shift method. The phase-shift method experimentally provides the link between the microscopic system of the Adsorption sites and process of OPD H on the atoms and the macroscopic system of the electrode kinetics and thermodynamics for OPD H at the interfaces. The phase-shift method can be effectively used as a new electrochemical method to determine or estimate Adsorption isotherms of intermediates for sequential reactions in electrochemical systems.
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determination of the Langmuir Adsorption isotherms of under and over potentially deposited hydrogen for the cathodic h2 evolution reaction at poly ir aqueous electrolyte interfaces using the phase shift method
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Sang K Jeon, Bok Ki Kim, Jin Y ChunAbstract:Abstract The Langmuir Adsorption isotherms of under-potentially deposited hydrogen (UPD H) and over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER) at poly-Ir /0.5 M H2SO4 and 0.05 M KOH aqueous electrolyte interfaces have been studied using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The behavior of the lagged phase shift (0°⩽−φ⩽90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1⩾θ⩾0) of H (UPD H, OPD H) for the cathodic HER at the interfaces. A linear relationship between the phase-shift profile (−φ vs. E) for the optimum intermediate frequency and the Langmuir Adsorption isotherm (θ vs. E) of H (UPD H, OPD H), i.e., the phase-shift method, can be used as a new electrochemical method to determine or estimate the fractional surface coverage (θ), equilibrium constant (K), and standard free energy (ΔGads0) of H (UPD H, OPD H) for the cathodic HER at the interfaces. At the poly-Ir /0.5 M H2SO4 aqueous electrolyte interface, K and ΔGads0 of the OPD H for the cathodic HER are 9.9×10−5 and 22.8 kJ/mol , respectively. At the poly-Ir /0.05 M KOH aqueous electrolyte interface, K and ΔGads0 of the UPD H for the cathodic HER are 3.9 and −3.4 kJ/mol , respectively. At the poly-Ir /0.05 M KOH aqueous electrolyte interface, K and ΔGads0 of the OPD H for the cathodic HER are 5.8×10−4 and 18.5 kJ/mol , respectively. The two different Langmuir Adsorption isotherms for H (UPD H, OPD H) correspond to two different Adsorption sites of H (UPD H, OPD H) on the poly-Ir electrode surface. The two different Adsorption sites of UPD H and OPD H act as two distinguishable electroadsorbed H species. The phase-shift method is a simple and efficient tool for determining the Adsorption, electrode kinetic, and thermodynamic parameters (θ, K, ΔGads0) of H (UPD H, OPD H) for the cathodic HER at the interfaces.
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determination of the equilibrium constant and standard free energy of the over potentially deposited hydrogen for the cathodic h2 evolution reaction at the pt rh alloy electrode interface using the phase shift method
International Journal of Hydrogen Energy, 2003Co-Authors: Jang H Chun, Sang K JeonAbstract:Abstract The Langmuir Adsorption isotherm of the over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER) at the Pt–Rh (Pt:Rh; 80: 20 wt % ) alloy /0.5 M H 2 SO 4 aqueous electrolyte interface has been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift (0°⩽− φ ⩽90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1⩾ θ ⩾0) of the OPD H for the cathodic HER at the interface. The phase-shift profile (− φ 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 ( θ vs. E ) of the OPD H for the cathodic HER at the interface. At the Pt–Rh alloy electrode interface, the equilibrium constant ( K ) and the standard free energy (Δ G ads ) of the OPD H are 2.2×10 −4 and 20.9 kJ / mol , respectively. At the steady state, the behaviors of the cyclic voltammogram and the Langmuir Adsorption isotherm of the OPD H for the cathodic HER at the Pt–Rh alloy electrode interface are similar to those of the pure Pt electrode interfaces. At the steady state, the effect of Rh on the OPD H for the cathodic HER can be neglected at the Pt–Rh (Pt:Rh; 80: 20 wt % ) alloy /0.5 M H 2 SO 4 aqueous electrolyte interface.
Milan B Radovanovic - One of the best experts on this subject based on the ideXlab platform.
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compounds from the imidazole group as copper corrosion inhibitor in acidic sodium sulphate solution
Zastita materijala, 2017Co-Authors: Ana T Simonovic, Milan B Radovanovic, Marija Mihajlovicpetrovic, Milan M AntonijevicAbstract:To estimate influence of 2-mercapto-1-methylimidazole and 4(5)methil-imidazole on electrochemical behaviour of copper electrode in 0.5 moldm-3 Na2SO4 solution, pH 3, following methods were used: open circuit potential measurements, potentiodynamic polarization, chronoamperometry. Potentiodynamic measurements showed that investigated inhibitors can be used as copper corrosion inhibitor in acidic 0.5 moldm-3Na2SO4 solution. Increase of concentrations leads to better inhibitor efficiency. These results were confirmed using the chronoamperometry. Adsorption of 2-mercapto-1-methylimidazole and 4(5)methil-imidazole obeys Langmuir Adsorption isotherm.
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the influence of synergistic effects of 5 methyl 1h benzotriazole and potassium sorbate as well as 5 methyl 1h benzotriazole and gelatin on the copper corrosion in sulphuric acid solution
Journal of Molecular Liquids, 2016Co-Authors: Zaklina Z Tasic, Milan M Antonijevic, Marija Mihajlovic, Milan B RadovanovicAbstract:Abstract The synergistic inhibition effect of the 5-methyl-1H-benzotriazole (MBTAH)/1H-benzotriazole (BTAH) with potassium sorbate and gelatin on the copper corrosion in an acidic sulphate solution was investigated by electrochemical methods and weight loss measurements. According to the obtained results, potassium sorbate and gelatin act as mixed-type inhibitors. The inhibition efficiency was significantly greater in the presence of MBTAH/BTAH with potassium sorbate or gelatin which indicates that synergistic inhibition effect was achieved. Investigated compounds obey Langmuir Adsorption isotherm.
Nam Y Kim - One of the best experts on this subject based on the ideXlab platform.
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the phase shift method for determining Langmuir and temkin Adsorption isotherms of over potentially deposited hydrogen for the cathodic h2 evolution reaction at the poly pt h2so4 aqueous electrolyte interface
International Journal of Hydrogen Energy, 2005Co-Authors: Jang H Chun, Nam Y Kim, Sang K Jeon, Jin Y ChunAbstract:Abstract A linear relationship between the behavior ( - ϕ vs. E ) of the phase shift ( 0 ∘ ⩽ - ϕ ⩽ 90 ∘ ) for the optimum intermediate frequency and that ( θ vs. E ) of the fractional surface coverage ( 1 ⩾ θ ⩾ 0 ) of over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER), i.e., the phase-shift method, at the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface has been verified using cyclic voltammetric, differential pulse voltammetric, and ac impedance techniques. The phase-shift method for determining the suitable Adsorption isotherm (Langmuir, Frumkin, Temkin) of OPD H for the cathodic HER at the interface also has been proposed. At the poly-Pt/0.5 M H 2 SO 4 aqueous electrolyte interface, the Langmuir Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( K = 1.3 × 10 - 4 ) for OPD H and the standard free energy ( Δ G ads 0 = 22.2 kJ / mol ) of OPD H are determined using the phase-shift method. At the same interface, the Temkin Adsorption isotherm ( θ vs. E ) of OPD H, the equilibrium constant ( 1.3 × 10 - 3 ⩾ K ⩾ 1.3 × 10 - 5 with θ , i.e., 0 ⩽ θ ⩽ 1 ) for OPD H, and the standard free energy ( 16.5 ⩽ Δ G θ 0 ⩽ 27.9 kJ / mol with θ , i.e., 0 ⩽ θ ⩽ 1 ) of OPD H are also determined using the phase-shift method. At the intermediate values of θ , i.e., 0.2 θ 0.8 , the Langmuir and Temkin Adsorption isotherms of OPD H for the cathodic HER at the interface are converted to each other. The equilibrium constant ( K 0 ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 10 times greater than that ( K ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). The interaction parameter ( g ) for the Temkin Adsorption isotherm ( θ vs. E ) is ca. 4.6 greater than that ( g ) for the corresponding Langmuir Adsorption isotherm ( θ vs. E ). These numbers (10 times and 4.6) can be taken as constant conversion factors between the corresponding Adsorption isotherms (Temkin, Langmuir, Frumkin). The Temkin Adsorption isotherm corresponding to the Langmuir or the Frumkin Adsorption isotherm, and vice versa, can be effectively converted using the constant conversion factors. Both the phase-shift method and constant conversion factors can be effectively used as a new electrochemical method to determine the suitable Adsorption isotherms (Langmuir, Frumkin, Temkin) of H for the cathodic HER in electrochemical systems.
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Langmuir Adsorption isotherms of overpotentially deposited hydrogen at poly au and rh h 2 so 4 aqueous electrolyte interfaces qualitative analysis using the phase shift method
Journal of The Electrochemical Society, 2003Co-Authors: Jang H Chun, Nam Y KimAbstract:The Langmuir Adsorption isotherms of over-potentially deposited hydrogen (OPD H) for the cathodic hydrogen evolution reaction (HER) at poly-Au and Rh/0.5 M H 2 SO 4 aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift (0° ≤ -Φ ≤ 90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1 ≥ θ ≥ 0) of OPD H for the cathodic HER at the interfaces. The phase-shift profile (-Φ 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 (θ as E) of the OPD H for the cathodic HER at the interfaces. At the poly-Au/(0.5 M H 2 SO 4 aqueous electrolyte interface, the equilibrium constant (K) and the standard free energy (ΔG ads )of the OPD H are 2.3 X 10 -6 and 32.2 kJ/mol, respectively. At the poly-Rh/0.5 M H 2 SO 4 aqueous electrolyte interface, K and ΔG ads, of the OPD H are 4.1 x 10 -4 or 1.2 X 10 -2 and 19.3 or 11.0 kJ/mol depending on E, respectively. In contrast to the poly-Au electrode interface, two different Langmuir Adsorption isotherms of OPD H are observed at the poly-Rh electrode interface. The two different Langmuir Adsorption isotherms of OPD H correspond to two different Adsorption sites of OPD H on the poly-Rh electrode surface.
