Visualization and Quantification of Electrochemical H₂ Bubble Nucleation at Pt, Au, and MoS₂ Substrates

Abstract

Electrolytic gas evolution is a significant phenomenon in many electrochemical technologies from water splitting, chloralkali process to fuel cells. Although it is known that gas evolution may substantially affect the ohmic resistance and mass transfer, studies focusing on the electrochemistry of individual bubbles are critical but also challenging. Here, we report an approach using scanning electrochemical cell microscopy (SECCM) with a single channel pipet to quantitatively study individual gas bubble nucleation on different electrode substrates, including conventional polycrystalline Pt and Au films, as well as the most interesting two-dimensional semiconductor MoS 2 . Due to the confinement effect of the pipet, well-defined peak-shaped voltammetric features associated with single bubble nucleation and growth are consistently observed. From stochastic bubble nucleation measurement and finite element simulation, the surface H 2 concentration corresponding to bubble nucleation is estimated to be ∼218, 137, and 157 mM, with critical nuclei contact angles of ∼156°, ∼161°, and ∼160°at polycrystalline Pt, Au, and MoS 2 substrates, respectively. We further demonstrated the surface faceting at polycrystalline Pt is not specifically correlated with the bubble nucleation behavior.

Differentiating electrochemically active regions of indium tin oxide electrodes for hydrogen evolution and reductive decomposition reactions. An in situ optical microscopy approach

“…Indeed, while the latter starts around -1.05 V, no bubbles are observed until overcoming a local critical concentration of dissolved H 2 . This corresponds to conditions to reach the saturation of the electrode surface with H 2 in order to initiate the nucleation of NBs on the ITO surface, as demonstrated in different systems related to HER from Pt nanoelectrodes or other catalytic NPs [26,49,50]. It is then expected that NBs are produced under H 2 mass transfer control, while the formation of ITO reduced NPs is rather driven by a surface transformation process.…”

Directly visualizing carrier transport and recombination at individual defects within 2D semiconductors

“…SECCM utilizes small, electrolyte-filled pipets as probes, creating miniaturized electrochemical cells. [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] By creating and interrogating a series of these cells in a "hoppingmode" fashion, images are constructed which reveal variations in the local electrochemical behavior of a sample. SECCM has been successfully employed to study the catalytic and photoelectrochemical properties of a variety of materials, including 2DSCs.…”

Recent progress in gas nanobubble electrochemistry

“…关于界面纳米气泡超长的稳 定性, 研究人员提出了多种不同的机理解释, 例如表 面污染物作用 [45] , 局部动态平衡理论 [46] 以及接触线固 定理论 [47] [49] ; (h) 水相和DMSO相中N 2 纳米气泡不同的电化学行 为 [51] (网络版彩图) [62] ; (b) 基于单通道毛细管 探针SECCM方法的H 2 微纳米气泡电化学研究示意图和规整峰状循环伏安图 [63] ; (c) 多晶型Pt表面的气泡成核电化学研究; (d) 多晶型Pt、Au及超薄MoS 2 基底上测得的气泡成核峰值电流i b p 分布直方图及基于有限元模拟得到的毛细管探针溶液内H 2 浓度 分布图 (网络版彩图) Figure 3 (a) SECCM approach for electrochemical studies of single H 2 bubble using a two-barrel glass pipet and the corresponding peak featured voltammogram [62]. (b) SECCM approach for electrochemical studies of single H 2 bubbles using a single-barrel glass pipet and the corresponding well-defined peak featured voltammogram [63]. 米气泡的几何形状结构, 但AFM成像中时间分辨率不 足 [66,67] .…”