This article presents a structure-based modeling approach to optimize gas evolution at an electrolyte-flooded porous electrode. By providing hydrophobic islands as preferential nucleation sites on the surface of the electrode, it is possible to nucleate and grow bubbles outside of the pore space, facilitating their release into the electrolyte. Bubbles that grow at preferential nucleation sites act as a sink for dissolved gas produced in electrode reactions, effectively suctioning it from the electrolyte-filled pores. According to the model, high oversaturation is necessary to nucleate bubbles inside of the pores. The high oversaturation allows establishing large concentration gradients in the pores that drive a diffusion flux towards the preferential nucleation sites. This diffusion flux keeps the pores bubble-free, avoiding deactivation of the electrochemically active surface area of the electrode as well as mechanical stress that would otherwise lead to catalyst degradation. The transport regime of the dissolved gas, viz. diffusion control vs. transfer control at the liquid-gas interface, determines the bubble growth law.

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Fuel-cell systems are of interest for a wide range of applications, in part for their utility in power generation from nonfossil-fuel sources. However, the generation of these alternative fuels, through electrochemical means, is a relatively inefficient process due to gas passivation of the electrode surfaces. Uniform microstructured nickel surfaces were prepared by photolithographic techniques as a systematic approach to correlating surface morphologies to their performance in the electrochemically driven oxygen evolution reaction (OER) in alkaline media. Hexagonal arrays of microstructured Ni cylinders were prepared with features of proportional dimensions to the oxygen bubbles generated during the OER process. Recessed and pillared features were investigated relative to planar Ni electrodes for their influence on OER performance and, potentially, bubble release. The arrays of cylindrical recesses were found to exhibit an enhanced OER efficiency relative to planar nickel electrodes. These microstructured electrodes had twice the current density of the planar electrodes at an overpotential of 100 mV. The results of these studies have important implications to guide the preparation of more-efficient fuel generation by water electrolysis and related processes.

Dynamic hydrogen bubble templating of Ni (Ni DHBT) electrodes was used to prepare highly porous films with enhanced properties towards the oxygen evolution reaction (OER). Upon varying the electrodeposition conditions, Ni films with a macroporous primary structure and highly porous cauliflower-like secondary structure were formed. These films are able to develop an extended electrochemically active surface area, up to 270-fold increase compared to Ni plate. They exhibit stable overpotential ( 250 = 540 mV) at j = 250 mA cm-2 geometric in 1M KOH electrolyte, which is 300 mV less positive than at Ni plate. Fe incorporation onto these Ni DHBT structures can further lower OER overpotentials to  250 = 310 mV. Ni DHBT films are remarkably stable over prolonged polarization and are characterized by a low Tafel slope (29 mV/ decade) that extends up to j =100 mA cm-2 geometric , attributed to both superaerophobic characteristics with a contact angle of ca 160° between the surface and an air bubble and superhydrophilic characteristics with less than 25° between the surface and a water droplet.

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