Low Temperature Oxidation Kinetics of Anodic Films on Lead in Sulfuric Acid Solution

Abstract

A multiphase model of anodic films on lead in sulfuric acid, previously developed to describe the oxidation of lead at room temperature, has been applied to potentiostatic transient data at very low temperatures (0° to −50°C). Freezing of the dilute pore electrolyte is proposed, such that ionic diffusion and equilibria must occur in a thin layer of adsorbed water between the ice and pore walls The experimentally determined activation energies and entropies of diffusion indicate that desorption of water or dehydration of ions plays an important role in the activation process. Except for the effects of the more limited electrolyte volume within the pores upon freezing, the electro‐oxidation processes follow a similar sequence above and below the freezing point. However, eventual reactant depletion, due to kinetically hindered equilibria and reduced electrolyte volume in the pores, leads to cessation of charge acceptance at very low temperatures, before appreciable β‐PbO2 formation can occur.

Hierarchical MnO2/NiS–MnS with Rich Electro-Microstructural Physiognomies for Highly Efficient All-Solid-State Hybrid Supercapacitors

“…To assess the contribution from semi-infinite diffusion-controlled and surface-controlled processes, eqs and have been closely examined. , i = k 1 ν + k 2 ν 1 / 2 i ν 1 / 2 = k 1 ν 1 / 2 + k 2 where i (in mA) refers to the anodic current and ν (in mV s –1 ) refers to the voltage sweep rate. Here, k 1 and k 2 are the process constants. , In the linear-fitted i /ν 1/2 vs ν 1/2 plot, the slope and intercept correspond to the process constants k 1 and k 2 , respectively, which technically correspond to the surface-controlled and semi-infinite diffusion-controlled processes, respectively . On applying the estimated values of k 1 and k 2 from the i /ν 1/2 vs ν 1/2 plot in eq for each scan rate and the corresponding anodic peak current, the capacitance contributions from surface-controlled and semi-infinite diffusion-controlled processes to the overall specific capacitance of MnO 2 /Ni–Mn–S have been estimated. , The estimated values of semi-infinite diffusion-controlled specific capacitance contribution to the overall specific capacitance of MnO 2 /Ni–Mn–S are found to be 97, 96, 96 95, and 94% at respective sweep rates of 10, 20, 30, 40, and 50 mV s –1 .…”

“…Here, k 1 and k 2 are the process constants. , In the linear-fitted i /ν 1/2 vs ν 1/2 plot, the slope and intercept correspond to the process constants k 1 and k 2 , respectively, which technically correspond to the surface-controlled and semi-infinite diffusion-controlled processes, respectively . On applying the estimated values of k 1 and k 2 from the i /ν 1/2 vs ν 1/2 plot in eq for each scan rate and the corresponding anodic peak current, the capacitance contributions from surface-controlled and semi-infinite diffusion-controlled processes to the overall specific capacitance of MnO 2 /Ni–Mn–S have been estimated. , The estimated values of semi-infinite diffusion-controlled specific capacitance contribution to the overall specific capacitance of MnO 2 /Ni–Mn–S are found to be 97, 96, 96 95, and 94% at respective sweep rates of 10, 20, 30, 40, and 50 mV s –1 . In this context, the plot of specific capacitance contribution (from semi-infinite diffusion-controlled and surface-controlled) to the overall specific capacitance of MnO 2 /Ni–Mn–S vs scan rate is presented in Figure C.…”

“…Here, k 1 and k 2 are the process constants. 56,57 In the linear-fitted i/ν 1/2 vs ν 1/2 plot, the slope and intercept correspond to the process constants k 1 and k 2 , respectively, which technically correspond to the surfacecontrolled and semi-infinite diffusion-controlled processes, respectively. 58 On applying the estimated values of k 1 and k 2 from the i/ν 1/2 vs ν 1/2 plot in eq 3 for each scan rate and the corresponding anodic peak current, the capacitance contributions from surface-controlled and semi-infinite diffusioncontrolled processes to the overall specific capacitance of MnO 2 /Ni−Mn−S have been estimated.…”

“…57,58 The estimated of semi-infinite diffusion-controlled specific capacitance contribution to the overall specific capacitance of MnO 2 /Ni− Mn−S are found to be 97, 96, 96 95, and 94% at respective sweep rates of 10, 20, 30, 40, and 50 mV s −1 . In this context, the plot of specific capacitance contribution (from semi-infinite diffusion-controlled and surface-controlled) to the overall specific capacitance of MnO 2 /Ni−Mn−S vs scan rate is presented in Figure…”

Characterization of Oxidation Product Films on Lead in Aqueous Media by In Situ Raman Spectroscopy

“…Today this property gives lead cotisiderable use in the chemical industry (3,47). While it is well known that the corrosion resistance is due to thin surface films, these have only been examined in detail in sulfuric acid solutions (48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60) and, to a lesser extent, in hydrochloric acid (61-64).…”