Electrolytically Generated Nanobubbles on Highly Orientated Pyrolytic Graphite Surfaces

Abstract

Electrolysis of water is employed to produce surface nanobubbles on highly orientated pyrolytic graphite (HOPG) surfaces. Hydrogen (oxygen) nanobubbles are formed when the HOPG surface acts as a negative (positive) electrode. The coverage and volume of the nanobubbles increase with increasing voltage. The yield of hydrogen nanobubbles is much larger than the yield of oxygen nanobubbles. The growth of the individual nanobubbles during the electrolysis process is recorded in time with the help of AFM measurements and correlated with the total current. Both the size of the individual nanobubbles and the total current saturate typically after 1 min; then the nanobubbles are in a dynamic equilibrium, meaning that they do not further grow, in spite of ongoing gas production and nonzero current. The surface area of nanobubbles shows a good correlation with the nanobubble volume growth rate, suggesting that either the electrolytic gas emerges directly at the nanobubbles' surface or it emerges at the electrode's surface and then diffuses through the nanobubbles' surface. Moreover, the experiments reveal that the time constants of the current and the aspect ratio of nanobubbles are the same under all conditions. Replacement of pure water by water containing a small amount of sodium chloride (0.01 M) allows for larger currents, but qualitatively gives the same results.

Total-Internal-Reflection-Fluorescence Microscopy for the Study of Nanobubble Dynamics

“…The downside is the long scanning time which prevents a study of their short time dynamics. Higher temporal resolution has been achieved with single line scans of the AFM tip [4] or with IR spectroscopy, e.g., Refs. [5,6].…”

Formation of Surface Nanobubbles and the Universality of Their Contact Angles: A Molecular Dynamics Approach

“…This means that the equilibrium simulations in this study need to be adapted to contain such a driving force. Such non-equilibrium effects include the presence of a thermal gradient (which are likely to be present in experimental setups as well) or the formation of gas at the substrate (which has been studied using electrolysis [25][26][27] Outlook. In conclusion, we have generated and analysed the formation and stability of surface nanobubbles in simple fluids.…”

Effect of impurities in the description of surface nanobubbles: Role of nonidealities in the surface layer

“…First, we consider BHBC 16 (of the general class BHBC n ) and the results from both the present model as well as our previous model [19] (without nonideality consideration) are compared with the experimental results [see Fig. 2(a)].…”

“…Sodium dodecyl sulphate (SDS) 2600 4000 2.85 × 10 16 . The experimental result (obtained from [40,41]) is shown by open squares, whereas the simulation result is denoted by continuous lines (the case with nonideality is represented by bold lines whereas that without nonideality is represented by dashed lines).…”

“…Over the past decade, there has been large number of investigations studying the formation, the properties, and the applications of these bubbles [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Most of these studies are nicely summarized in a couple of recent review articles [17,18].…”