Visualization and Quantification of Electrochemical H2 Bubble Nucleation at Pt, Au, and MoS2 Substrates

Electrolytic gas evolution is a significant phenomenon in many electrochemical technologies from water splitting, chloralkali process to fuel cells. Although it is known that gas evolution may substantially affect the ohmic resistance and mass transfer, studies focusing on the electrochemistry of individual bubbles are critical but also challenging. Here, we report an approach using scanning electrochemical cell microscopy (SECCM) with a single channel pipet to quantitatively study individual gas bubble nucleation on different electrode substrates, including conventional polycrystalline Pt and Au films, as well as the most interesting two-dimensional semiconductor MoS2. Due to the confinement effect of the pipet, well-defined peak-shaped voltammetric features associated with single bubble nucleation and growth are consistently observed. From stochastic bubble nucleation measurement and finite element simulation, the surface H-2 concentration corresponding to bubble nucleation is estimated to be similar to 218, 137, and 157 mM, with critical nuclei contact angles of similar to 156 degrees, similar to 161 degrees, and similar to 160 degrees at polycrystalline Pt, Au, and MoS2 substrates, respectively. We further demonstrated the surface faceting at polycrystalline Pt is not specifically correlated with the bubble nucleation behavior.

Automated summary

The study quantitatively investigated individual gas bubble nucleation on different electrode substrates using scanning electrochemical cell microscopy (SECCM) with a single channel pipet, revealing the nucleation and growth process of bubbles.