pycex

pycex is a small electrochemistry package for Tafel and Butler-Volmer analysis from measurement data.

Installation

For now installation has to be done manually by the user but publishing of the library is planned as soon as its finished.

Scope

pycex expects the user to import files and prepare arrays externally. It does not include a dedicated IO layer.

Overpotential

pycex treats overpotential as:

eta = E - E_eq

You can construct ElectrochemData in either of these two ways:

ElectrochemData(eta=eta, current_density_A_cm2=j)

or

ElectrochemData(
    potential_V=E,
    equilibrium_potential_V=E_eq,
    current_density_A_cm2=j,
)

Quick start

import numpy as np
from pycex import ButlerVolmerFit, ElectrochemData, TafelFit

E = np.linspace(-0.12, 0.12, 121)
E_eq = 0.0
j = 1e-6 * (
    np.exp(0.5 * 96485.33212 / (8.31446261815324 * 298.15) * (E - E_eq))
    - np.exp(-0.5 * 96485.33212 / (8.31446261815324 * 298.15) * (E - E_eq))
)

data = ElectrochemData(
    potential_V=E,
    equilibrium_potential_V=E_eq,
    current_density_A_cm2=j,
)

tafel = TafelFit(data, eta_min_abs=0.03, eta_max_abs=0.12).analyze().summary
bv = ButlerVolmerFit(data, eta_min_abs=0.0, eta_max_abs=0.12).analyze().result

Notes

• eta is overpotential in volts
• j is current density in A cm^-2
• The conventional sign convention is assumed: anodic current positive and cathodic current negative
• If needed, iR correction should be handled before constructing ElectrochemData