Investigation of electrolytic hydrogen nanobubbles behavior on heterogeneous wettability surface by using molecular dynamics simulation

The electrolytic hydrogen nanobubbles with growth and adhesion undesirably block the gas-evolving electrodes, thus increasing the extra overpotential and reducing the energy conversion efficiency. Therefore, a deep understanding of the nanobubbles behaviors on the electrode surface with different wettability patterns at a microscopic level is crucial for the design of efficient electrochemical devices and the preparation of the hyperactive nanocatalysts structures. To clarify the electrolytic nanobubbles behavior on the heterogeneous wettability surface of the entire solid substrate, the nanoelectrode is made hydrophobic to water and the surrounding solid plate is made hydrophilic to water. The effects of the conversion rate F and surface wettability of the surrounding solid plate (ɛ_w-s) on the nanobubble growth behavior and the stability or instability mechanisms were investigated by combining molecular dynamics (MD) simulations and theoretical analysis with a mature and advisable dynamic equilibrium model. The simulated both peak and residual currents agree well with experimental data and previous MD simulations results. The nanobubbles morphology, size and pinning behavior, as well as the stability or instability characteristics have a close connection with ɛ_w-s and F. When ɛ_w-s is approximately lower than a threshold value, the stable nanobubbles after a limited growth will be obtained for any F. The stable nanobubbles are also easily formed for very low F and higher ɛ_w-s. The growing nanobubbles are more likely to become unstable and eventually detach from the electrode surface for the slightly larger F and higher ɛ_w-s.