MECHANISM 2 • PSEUDOCAPACITANCE

Charge that crosses the interface

🔁

Pseudocapacitance stores energy through quick, reversible faradaic reactions at or near the electrode surface. Unlike an EDLC, electrons actually transfer between the electrode and electrochemically active species — which allows far more charge to be stored.

Faradaic just means electron transfer across the interface — real, but reversible, chemistry.

MECHANISM 2 • PSEUDOCAPACITANCE

Fast because it stays shallow

Redox reactions

Reversible oxidation and reduction

Ion intercalation

Ions slip into the near-surface material

Electrosorption

Ions adsorb with partial charge transfer

These reactions are confined to the near-surface region, not the bulk — so kinetics stay fast and power stays high.

MECHANISM 2 • PSEUDOCAPACITANCE

Pseudocapacitive materials

Metal oxides Ruthenium oxide (RuO₂), manganese oxide (MnO₂)

Conducting polymers Polyaniline (PANI), polypyrrole (PPy), PEDOT

These offer electrochemically active sites for reversible charge transfer, giving capacitance well beyond what double-layer storage alone achieves.

THE TRADEOFF

More storage, less endurance

EDLC

Exceptional cycle life and power, but lower capacitance.

Pseudocapacitor

Higher capacitance and energy density, but repeated redox reactions and structural changes reduce cycling stability.

Many modern designs combine both mechanisms to get the best of each.

UNIT 7 STUDY COMPLETE

🧲

Ready for the Fab Challenge?

You've covered fast, reversible redox reactions that store more charge — at a cost.