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Polarisation Losses in Electrochemical Cells
About This Visualisation
Real electrochemical cells (fuel cells, electrolysers, batteries) experience voltage losses due to polarisation effects. This interactive tool demonstrates how three main types of losses affect cell performance in both operating modes:
- Galvanic Mode (Fuel Cell/Battery): Spontaneous reactions generate electricity. Polarisation losses cause voltage to decrease as current increases.
- Electrolytic Mode (Electrolyser): Applied voltage drives non-spontaneous reactions. Polarisation losses cause required voltage to increase as current increases.
The three loss types:
- Activation Loss: Energy barrier for electrochemical reactions (most significant at low currents)
- Ohmic Loss: Resistance to ion flow through electrolyte and electron flow through components (linear with current)
- Concentration Loss: Depletion of reactants at electrode surface (dominates at high currents)
Switch between modes and toggle each loss type to see how they combine in both galvanic and electrolytic operation!
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Control Loss Components
Spontaneous reaction: Voltage decreases as current increases
Controls the height of the activation energy barrier
Controls the slope of the linear voltage drop
Controls when mass transport limitations begin
Understanding the Losses in Both Modes
Galvanic Mode (Fuel Cells, Batteries Discharging): Spontaneous reactions. Cell voltage decreases from reversible potential as current increases due to polarisation losses.
Electrolytic Mode (Electrolysers, Batteries Charging): Non-spontaneous reactions. Applied voltage must exceed reversible potential, and required voltage increases with current due to the same polarisation losses.
- Activation Loss (Kinetic): Dominates at low current densities. Caused by the energy needed to initiate electrochemical reactions. Better catalysts reduce this loss.
- Ohmic Loss (Resistive): Constant slope across all currents. Caused by resistance to ion movement in electrolyte and electron flow in conductors. Thinner, more conductive electrolytes reduce this loss.
- Concentration Loss (Mass Transport): Dominates at high current densities. Caused by inability to supply reactants fast enough to electrode. Better flow fields and higher reactant concentrations reduce this loss.
Design Goal: Minimise all three losses to maximise cell efficiency and power output (galvanic) or minimise energy consumption (electrolytic)!