Hydrogen Bubble Size Distribution on Nanostructured Ni Surfaces: Electrochemically Active Surface Area Versus Wettability

Emerging manufacturing technologies make it possible
to design
the morphology of electrocatalysts on the nanoscale in order to improve
their efficiency in electrolysis processes. The current work investigates
the effects of electrode-attached hydrogen bubbles on the performance
of electrodes depending on their surface morphology and wettability.
Ni-based electrocatalysts with hydrophilic and hydrophobic nanostructures
are manufactured by electrodeposition, and their surface properties
are characterized. Despite a considerably larger electrochemically
active surface area, electrochemical analysis reveals that the samples
with more pronounced hydrophobic properties perform worse at industrially
relevant current densities. High-speed imaging shows significantly
larger bubble detachment radii with higher hydrophobicity, meaning
that the electrode surface area that is blocked by gas is larger than
the area gained by nanostructuring. Furthermore, a slight tendency
toward bubble size reduction of 7.5% with an increase in the current
density is observed in 1 M KOH.