Hexagonal Arrays of Cylindrical Nickel Microstructures for Improved Oxygen Evolution Reaction

Abstract

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.

Regular Dimpled Nickel Surfaces for Improved Efficiency of the Oxygen Evolution Reaction

“…In a prior study on structure-function correlations of the OER, cylindrical recesses (~1-µm depth and 20-µm diameter) were found to have a higher activity towards the OER when compared to planar nickel electrodes. 19 The cylindrical recesses were also capable of reducing bubble adhesion under a lateral shear flow as predicted by Weber number calculations. In the case of a motionless electrolyte, confined geometries are likely to be more significantly impacted by changes in fluid dynamics from bubble-induced microconvection.…”

“…Many electrodes with a roughened surface morphology have exhibited an improved electrocatalytic activity, but very few studies have simultaneously demonstrated control over geometric surface features. [16][17][18][19] In the absence of controlling the surface geometry, it is difficult to determine with absolute certainty what the specific contributions are from each factor that influences the observed enhancement in activity.…”

Influence of Electrochemical Aging on Bead-Blasted Nickel Electrodes for the Oxygen Evolution Reaction

“…Periodic oscillations in the data indicate the release of oxygen bubbles from the electrodes. 24,25 The electrodes treated by steady-state aging exhibited lower potentials in the CP measurements and a smaller amplitude in the oscillations of these potentials over time. During the OER, a higher efficiency for the generation and release of bubbles was observed for the electrodes treated by the steady-state aging process.…”

“…23 Although the wetting properties of microscale textures are less well-studied, these textures have demonstrated enhanced gas evolution dynamics (e.g., bubble nucleation, coalescence, and release events). [24][25][26] In addition, there are only a few reported examples that evaluate the efficiency of gas evolution reactions for microstructures prepared over large areas. 22,27,28 Electrodeposition is a widely used technique that can produce microscale textures over large areas.…”

Nitrogen-Doped Sponge Ni Fibers as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

“…Owing to the huge concerns associated with serious environmental pollution and rapid fossil energy consumption, the development of clean and renewable energy technologies has become a vital task [1][2][3][4]. The oxygen evolution reaction (OER), as a key process in water splitting and rechargeable metal-air batteries, has attracted considerable attention for decades [5][6][7][8][9][10][11][12][13][14]. However, the OER is a kinetically sluggish process with a high overpotential, which calls for efficient electrocatalysts that can reduce the overpotential and improve the reaction efficiency [15][16][17][18][19].…”