Assessing the electron transfer and oxygen mass transfer of the oxygen reduction reaction using a new electrode kinetic equation

Abstract

The oxygen reduction reaction (ORR), which is widely employed for energy harvesting and environmental purification, requires an electrode kinetic equation for assessing the electron transfer (ET) and oxygen mass transfer (OMT). Herein, we establish a new kinetic equation in conjunction with the ET kinetics and OMT flux, creating a parameter (kO2) characterizing the effect of OMT. This equation allows for the nonlinear fitting of polarizations in full scale and outputs reliable parameters, including α (ET coefficient), j0 (exchange current density) and kO2. The performance is superior to the Tafel equation by outputting reliable values of α and j0, and covers the function of the Koutecky-Levich equation to calculate the electron transfer number (n) as well. Furthermore, by means of kO2, the assessment of OMT becomes available, disclosing the facilitating effect brought about by the porous structure on the ORR rate. Consequently, the new equation provides a reliable and facile approach for assessing the performance of electrode reaction systems and electrocatalysts.

Highly efficient electrosynthesis of hydrogen peroxide on a superhydrophobic three-phase interface by natural air diffusion

“…4e). It increased linearly with increasing current density, but basically remained unchanged at the current density of 60 mA cm −2 , indicating that H 2 O 2 production turned into oxygen mass transfer controlled when the current density was higher than this point 10 . Assuming the OUE of 100%, the minimum O 2 diffusion coefficient of the diffusion layer was predicted to be 0.75 × 10 −1 cm 2 s −1 , meaning the actual O 2 diffusion coefficient of the porous diffusion layer should be between 0.75 × 10 −1 and 2 × 10 −1 cm 2 s −1 (the O 2 diffusion coefficient in air 35 ) and agreed with our calculation.…”

“…For those H 2 O 2 -based electrochemical advanced oxidation processes (EAOPs), e.g., electro-Fenton (EF) and photoelectro-Fenton (PEF), efficient H 2 O 2 production is particularly important, which can promote the formation of hydroxyl radicals to degrade organic pollutants 8,9 . Catalyst selectivity, oxygen mass transfer, and electron transfer at the cathodic reaction interface are three important factors for achieving efficient H 2 O 2 production 10 . Carbonaceous materials, including carbon black (CB), nanotubes, and graphene, have been proved to be good ORR catalysts for H 2 O 2 synthesis 11,12 .…”

Systematic Study of Effective Hydrothermal Synthesis to Fabricate Nb-Incorporated TiO2 for Oxygen Reduction Reaction

“…where I is the measured current density, IK is the kinetic-limiting current density, diffusion-limiting current density, A is the surface area of the electrode, ω is the velocity of the electrode, F is the Faraday constant (96 485 C/mol), DO is the diffu efficient of O2 in the electrolyte (1.87 × 10 −5 cm 2 /s), ν is the kinematic viscosity (0.0 of the electrolyte, and C0 is the bulk concentration of O2 in the electrolyte (1.2 mol/cm 2 ) [34]. In this study, for a comparison, a Pt/C suspension was also prepa dropped on the RDE as a benchmark following the same procedure as described The LSV rotation speed was 1600 rpm, and Pt/C (20 wt% Pt loading on Vulcan XC purchased from Sigma-Aldrich.…”

“…The CV and LSV curves were measured at scan rates of 100 and 10 mV/s, respectively. Herein, from the results of LSV curves, the n involved in the ORR process can be calculated through the Koutecký–Levich (K–L) plots, using the following equations [ 32 , 33 ]: where I is the measured current density, I K is the kinetic-limiting current density, I D is the diffusion-limiting current density, A is the surface area of the electrode, ω is the angular velocity of the electrode, F is the Faraday constant (96,485 C/mol), D O is the diffusion coefficient of O 2 in the electrolyte (1.87 × 10 −5 cm 2 /s), ν is the kinematic viscosity (0.01 cm 2 /s) of the electrolyte, and C 0 is the bulk concentration of O 2 in the electrolyte (1.21 × 10 −6 mol/cm 2 ) [ 34 ]. In this study, for a comparison, a Pt/C suspension was also prepared and dropped on the RDE as a benchmark following the same procedure as described above.…”

Upscaled model for diffusion and serial reduction pathways in porous ​electrodes

“…A more formal derivation of a macroscopic model for transport and reaction in a porous electrode, taking into account the solid, fluid and gas phases, was reported by Vidts and White [24], without however any closure allowing an accurate estimate of the effective diffusivity. A new electrode kinetic equation for a non-porous electrode was recently developed on the basis of a coupled model of electron transfer obeying a Butler-Volmer relationship and oxygen mass transfer at steady-state in the case of direct oxygen reduction [25]. For a thorough analysis of the macroscopic behavior and, further, in the perspective of an optimization of the devices under concern, a rational approach, based on a cautious derivation of appropriate macroscopic models from the physicoelectrochemical governing equations at the underlying microscopic scale is of major importance.…”