Bubble size distribution and electrode coverage at porous nickel electrodes in a novel 3-electrode flow-through cell

TL;DR

This study introduces a new three-electrode flow-through cell to analyze bubble size and electrode coverage during hydrogen evolution on porous nickel electrodes, revealing how flow and current density affect bubble dynamics.

Contribution

The paper presents a novel experimental setup combining electrochemical and optical methods to study bubble behavior on porous electrodes under various flow and current conditions.

Findings

Flow reduces bubble size at moderate current densities.

Current density influences bubble detachment and coverage.

Transient bubble coverage is minimally affected by flow.

Abstract

A novel 3-electrode cell type is introduced to run parametrical studies of H$_2$ evolution in an alkaline electrolyte on porous electrodes. Electrochemical methods combined with a high-speed optical measurement system are applied simultaneously to characterize the electrodes and the bubble dynamics in terms of bubble size distribution and coverage of the working electrode. Three different cathodes made of expanded nickel are investigated at applied current densities of |j| = 10 to 200 mA cm$^{-2}$ without forced flow and at a flow rate of 5 ml min$^{-1}$. The applied current density is found to significantly influence both the size of detached bubbles and the surface coverage of the working electrode. The forced flow through the cathodes is found to strongly reduce the bubble size up to current densities of about 100 mA cm$^{-2}$, whereas the initial transient until the cathode surface is completely covered by bubbles is only marginally affected by the flow-through.