In Operando Visualization and Dynamic Manipulation of Electrochemical Processes at the Electrode–Solution Interface

Abstract

Revealing the dynamic processes at the electrode–solution interface is imperative for understanding electrochemical phenomena. Most techniques have been developed to sense the electrode surface changes at the nanoscale, but provide limited information on potential‐induced interfacial ion redistribution at the mesoscale. Herein, we present an in operando visualization method utilizing a microfabricated electrochemical cell combined with a laser scanning confocal microscope to observe high‐resolution and fast‐response interfacial processes. We report potential‐induced formation and transformation of the Nernst diffusion layer, demonstrating that pulsed voltage dynamically perturbs the interface and promotes ion diffusion. This provides an additional insight into developing a dynamic manipulation method to control the electrochemical process. Our novel visualization method can easily be applied to monitor different ionic behaviors in electrochemical reactions at the mesoscale.

Pulsed-waveform electrocatalytic detoxification of hexavalent chromium promoted by pseudocapacitive effects

“…The impact of the pulsed frequency on Cr(VI) detoxication can be attributed to three aspects: the interfacial ion diffusion, electrode reaction selectivity, and electron transfer rate of PANI. The potentialinduced interfacial ionic behaviors were directly observed in our recent study, 17 which conrmed the occurrence of concentration polarization at the constant voltage and the periodic renewal of ions in the diffusion layer at the pulsed voltage with 0.1-0.5 Hz. The t off of each pulsed cycle promoted the replenishment of Cr(VI) at the cathode and the diffusion of the generated Cr(III) to the bulk solution (Fig.…”

“…This is because the diffusion process slowed and eventually reached equilibrium along with the reducing concentration gradient and renewal of the diffusion layer, as observed in our recent study. 17 The Cr(VI) reduction efficiencies with varying durations of t on and t off at a xed on-off ratio were further investigated. Specically, with an on-off ratio of 20%, the reduction efficiencies of t on : t off = 1 s : 4 s, 0.4 s : 1.6 s, and 0.2 s : 0.8 s were 82.6%, 65.6%, and 52.0%, respectively, which are considerably higher than that under the constant condition (29.1%) (Fig.…”

“…15,16 In our recent study it was observed that the pulsed voltage with periodic pauses promoted ion diffusion and cyclically renewed the diffusion layer, in turn enhancing mass transport and reducing concentration polarization. 17 This is highly advantageous for diffusion-controlled reactions to break down the barrier of concentration gradients across the interface for the effective replenishment of the electrode surface with reactants and for product release from the interface. 18 However, the electrode reaction is suspended in the offvoltage stage of a pulse cycle, which reduces the overall reaction rate.…”

Selective Oxygen Activation to Reactive Oxygen Species on a Carbon Layer-Encapsulated CuxO Electrocatalyst for Water Purification

“…To unveil the intrinsic mechanism of ROS generation via the selective OA reaction on Cu x O@C, we first observed the dynamic change process of OA by in situ electrochemical fluorescence (Figure S14) and Raman (Figure S15) measurements. , As shown in Figure a, the solution pH near the Cu x O@C electrode surface increased slightly as the reaction went on at oxygen saturation, indicating that the O 2 could be activated on Cu x O@C. In addition, there were strong fluorescence signals of H 2 O 2 and • OH on the Cu x O@C electrode surface as the reaction went on at oxygen saturation, meaning abundant H 2 O 2 and • OH production (Figure S16), which further confirmed the high activity of Cu x O@C for the selective OA reaction. It was clear that there were three significant diffraction peaks located at ∼993, ∼741, and ∼778 cm –1 , which belonged to the O–O stretching vibration of *O 2 , *OOH/H 2 O 2 , and *H 3 O 2 (critical intermediate in the process of • OH production), respectively, proving the high activity of Cu x O@C for the selective OA reaction again (Figure b) .…”

Recent Advances and Performance Enhancement Mechanisms of Pulsed Electrocatalysis

“…因此, 发展实验表征手段获取脉冲电催化期间电 极表面附近物质浓度的时空分布是必要的. 值得一提的 是, 最近 Xin 等 [102] 将微加工电解池与激光扫描共聚焦 显微镜结合, 可以在高空间分辨率下观察电极-溶液界 面发生的动态过程. 他们发现, 当电压恒定时, 扩散层 会由于反应物的消耗和产物的富集而在电极-溶液界面 形成浓度梯度; 而当施加脉冲电压时, 则可以通过促进 界面离子扩散来有效地更新扩散层.…”