Python code for Randles-Sevcik Equation

# -*- coding: utf-8 -*-

"""

Created on Sun Jan  5 10:50:40 2025

 

@author: martp

"""

 

import numpy as np

import matplotlib.pyplot as plt

 

# Constants

n = 1  # Number of electrons transferred

A = 0.0416  # Electrode area in cm²

D = 6.0e-6  # Diffusion coefficient in cm²/s

C_mol_L = 5e-3  # Concentration in mol/L

blocking = 0.0  # Fraction of the electrode area blocked (0.5 means 50% blocked)

F = 96485  # Faraday constant in C/mol

R = 8.314  # Gas constant in J/(mol*K)

T = 298  # Temperature in K

 

# Convert concentration from mol/L to mol/cm³

C = C_mol_L / 1000  # 1 L = 1000 cm³

 

# Adjust the effective electrode area due to blocking

effective_area = A * (1 - blocking)  # Effective area after blocking

 

# Randles-Sevcik constant at 298 K

k = 2.69e5  

 

# Scan rates in V/s (logarithmic range for better visualization)

v = np.logspace(-3, 1, 500)  # From 0.001 to 10 V/s

 

# Calculate peak current using Randles-Sevcik equation and convert to microamps

Ip_microA = k * n**1.5 * effective_area * D**0.5 * C * v**0.5 * 1e6  # Convert A to µA

 

# Plot

plt.figure(figsize=(8, 6))

plt.plot(v, Ip_microA, label=f'n={n}, Effective A={effective_area:.2f} cm², D={D} cm²/s, C={C_mol_L} mol/L, Blocking={blocking*100:.0f}%')

plt.xscale('log')  # Logarithmic scale for scan rate

plt.yscale('log')  # Logarithmic scale for peak current

plt.xlabel('Scan Rate (V/s)', fontsize=12)

plt.ylabel('Peak Current (µA)', fontsize=12)

plt.title('Randles-Sevcik Equation: Peak Current vs Scan Rate (With Blocking)', fontsize=14)

plt.grid(which='both', linestyle='--', linewidth=0.5)

plt.legend(fontsize=10)

plt.tight_layout()

plt.show()