Direct measuring of single–heterogeneous bubble nucleation mediated by surface topology

Abstract

Heterogeneous bubble nucleation is one of the most fundamental interfacial processes ranging from nature to technology. There is excellent evidence that surface topology is important in directing heterogeneous nucleation; however, deep understanding of the energetics by which nanoscale architectures promote nucleation is still challenging. Herein, we report a direct and quantitative measurement of single-bubble nucleation on a single silica nanoparticle within a microsized droplet using scanning electrochemical cell microscopy. Local gas concentration at nucleation is determined from finite element simulation at the corresponding faradaic current of the peak-featured voltammogram. It is demonstrated that the criteria gas concentration for nucleation first drops and then rises with increasing nanoparticle radius. An optimum nanoparticle radius around 10 nm prominently expedites the nucleation by facilitating the special topological nanoconfinements that consequently catalyze the nucleation. Moreover, the experimental result is corroborated by our theoretical calculations of free energy change based on the classic nucleation theory. This study offers insights into the impact of surface topology on heterogenous nucleation that have not been previously observed.

Single-Entity Electrochemistry of Nano- and Microbubbles in Electrolytic Gas Evolution

“…We speculate the fast gas-exchange at the liquid–air interface at the nanoscopic droplet quickly dissipates the local gas supersaturation. Our group carried out a modified electrochemical study of bubble nucleation using a single-barrel micropipette. − Remarkably, the peak-shaped voltammograms with well-defined peak current i b p and stable residual current were found to be consistent over multiple measurements at the same location, as well as for micropipettes with radius from 1 to 10 μm (Figure b). Subsequently, electrochemical imaging of bubble nucleation across planar surfaces ranging from polycrystalline Pt to Au and ultrathin MoS 2 film was performed to understand the physicochemical properties of the heterogeneous nucleation and their dependence on surface properties and grain boundaries (Figure c).…”

“…More recently, Chen and co-workers utilized the SECCM technique to investigate single-bubble nucleation on a nanoparticle and clarify an unprecedented nanoscopic surface topological basis of heterogeneous bubble nucleation . Individual electrochemically inert silica nanoparticles were immobilized on a flat glassy carbon surface and encompassed within a microsized meniscus droplet, acting as perfect foreign nucleants to tune the nucleation energetics (Figure ).…”

“…(a) Scheme of SECCM study of single gas bubble nucleation on a SiO 2 nanoparticle and the nucleation energetics . (b) Typical peak-featured voltammogram for H 2 bubble formation on bare GC surface and on a SiO 2 nanoparticle.…”

“…(c) The Gaussian peak position of nucleation current, ⟨ i b p ⟩, as a function of SiO 2 nanoparticle radius. Reprinted with permission from ref . Copyright 2022 PNAS.…”

“…This Perspective summarizes the recent advances in the quantitative measurement of single nano- and micrometer bubbles evolved in electrolytic gas evolution. The high temporal resolution and sensitive electrochemical ,,, and optical , signals for single bubbles reveal many never-before-seen insights concerning the heterogeneous nucleation, bubble dynamics, and mass transport at the gas–liquid–electrode three-phase boundary while the high spatial resolution provides unambiguous complementary local chemical/structural information on electrode surfaces. ,,, Through these operando or in situ explorations of single gas nano- and microbubbles, our understanding of the fundamental gas bubble phenomenon and its influence on electrolytic energy conversion has been significantly advanced.…”