Visualizing and quantifying local OER activity on stainless-steel mesh via gas bubble dynamics

The development of efficient, low-cost catalysts for the oxygen evolution reaction (OER) is critical for advancing sustainable energy technologies such as water electrolysis. Stainless steel mesh (SSM) is a promising alternative to precious metal catalysts, yet the spatial distribution of active sites on its surface remains poorly understood. Here, we introduce an in situ strategy that leverages oxygen bubble evolution dynamics to visualize and quantitatively probe localized OER activity on SSM model electrodes in real time. Time-resolved optical tracking of gas bubbles enables direct determination of local reaction rates, revealing that curved regions of the mesh, which experience compressive strain, exhibit markedly enhanced OER activity characterized by accelerated bubble nucleation and growth. In situ electrochemical Raman mapping reveals that these compressive domains promote the phase transition of nickel hydroxide to catalytically active nickel oxyhydroxide at lower potentials, attributed to a reduced energy barrier arising from the lattice contraction accompanying this phase change. This work establishes gas bubble dynamics as a powerful, spatially resolved tool for quantifying intrinsic electrocatalytic activity and uncovers compressive strain as a key factor governing active phase formation on stainless steel electrodes.