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.

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She holds Bachelor's (2017) and Master's (2020) degrees in physics from Guangxi University. She is currently working on structure−activity of catalysis and nanobubbles using scanning electrochemical cell microscopy.Yun Shan obtained her master's degree in the College of Chemistry, Chemical Engineering and Biotechnology, Donghua University in 2022. Her research was focused on the understanding of nucleation phenomena, including bubbles and particles.Yu Peng received his bachelor's degree in chemistry from Ludong University (2020) and is currently a second-year master's student in the College of Chemistry, Chemical Engineering and Biotechnology, Donghua University. He is working on single-particle electrocatalysis and dynamics.

Transition-metal (oxy)hydroxides are among the most active and studied catalysts for the oxygen evolution reaction in alkaline electrolytes. However, the geometric distribution of active sites is still elusive. Here, using the well-defined crystalline iron-substituted cobalt hydroxide as a model catalyst, we reported the scanning electrochemical cell microscopy (SECCM) study of single-crystalline nanoplates, where the oxygen evolution reaction at individual nanoplates was isolated and evaluated independently. With integrated prior- and post-SECCM scanning electron microscopy of the catalyst morphology, correlated structure–activity information of individual electrocatalysts was obtained. Our result reveals that while the active sites are largely located at the edges of the pristine Co(OH)2 nanoplates, the Fe lattice incorporation significantly promotes the basal plane activities. Our approach of correlative imaging provides new insights into the effect of iron incorporation on active site distribution across nano-electrocatalysts.