Bubble Dynamics during Hydrogen Evolution Reaction over Fluidizable Electrocatalyst Particles

Abstract

Gas bubble adhesion, a ubiquitous phenomenon in electrochemical gas-evolving reactions, reduces the hydrogen evolution reaction (HER) activity in water electrolysis. Understanding the dynamics of gas bubble detachment and its dependence on force balance is crucial for manipulating bubble departure, but it remains insufficiently investigated. Here, we found that bubble dynamics differ markedly between fluidizable and stationary electrocatalysts, with fluidizable electrocatalysts minimizing bubble adhesion and showing a 37-fold increase in the HER rate constant. This enhancement is attributed to accelerated bubble detachment driven by the fluidization effect of the electrocatalyst particles. Specifically, the transition from stationary to fluidizable electrocatalysts marks a shift from a flat to a particulate model, introducing promoting effects arising from particle movement and spin-induced centrifugal force and bubble collision-triggered coalescence. Consequently, the measured HER activity approaches its intrinsic value. This work highlights fluidization as an effective strategy to eliminate bubble adhesion, thereby exposing nearly all active sites to electrocatalytic reactions.