# Tuning Electrochemical Reactions with Ratchet-Based Ion Pumps

## TL;DR

This paper shows how ratchet-based ion pumps can control electrochemical reactions by adjusting ion flow near electrodes.

## Contribution

The novel use of ratchet-based ion pumps to modify electrochemical reaction rates and selectivity through ion potential control.

## Key findings

- RBIPs can accelerate or inhibit electrochemical reactions based on the input signal.
- Proton pumping prevents proton depletion and maintains pH near water-splitting electrodes.
- Combining ion pumping with selectivity allows precise tuning of electrolyte composition near electrodes.

## Abstract

Electrochemical reactions are highly sensitive to the
physical
and chemical environments near the electrodes. Thus, controlling the
electrolyte ionic composition and the electrochemical potential of
specific ions can modify the overpotential of electrochemical reactions
and enhance their selectivity toward the desired products. Ratchet-based
ion pumps (RBIPs) are membrane-like devices that utilize temporal
potential modulation to drive a net ionic flux with no associated
electrochemical reactions. RBIPs were fabricated by coating the surfaces
of nanoporous alumina wafers with metals, forming nanoporous capacitors.
Placing the RBIP between two electrolyte compartments and applying
an alternating signal between the metal layers resulted in a voltage
buildup across the membrane, leading to ion pumping. Here, we demonstrate
that by modifying the electrochemical potential of ions, RBIPs can
accelerate or inhibit electrochemical reactions on the surface of
adjacent water-splitting electrodes according to the RBIP input signal.
Proton pumping toward a water-splitting cathode prevented proton depletion
due to the hydrogen evolution reaction and maintained the pH in the
cathode compartment. The combination of ion pumping and ion selectivity
can enable the electrolyte composition to be tuned near the electrodes,
providing greater control over the electrochemical process.