Mode Scanning Electrochemical Microscopy Research Articles

Quantification of Surface Reactive Oxygen Species at Co-Modified BiVO4 with Surface Interrogation Mode of Scanning Electrochemical Microscopy

Ultrasensitive electrochemical and optical imaging approaches are critical for realizing local chemical information particularly for systems such as sustainable energy harvesting and conversion. Scanning electrochemical microscopy (SECM)-based electrochemical and spectroelectrochemical techniques will be described in this presentation to illustrate ultrasensitive quantitative analysis of catalytic surfaces and localized redox activities with improved spatial and spectral and temporal resolutions. Examples of SECM based on ultramicroelectrodes, nanoelectrodes, and optical fiber electrodes and optical imaging techniques will be discussed. These techniques help understanding fundamental aspects of an electrochemical process, such as local heterogeneities in catalytic reaction and stability issues of functional low-dimension metallic and semiconductor electrode materials with synergistic functions for sunlight harvesting, conversion, and storage into chemical fuels. These studies will provide insights into developing unique catalytic and photonic properties of nanostructured electrode materials for the efficient and selectivity of the solar-to-fuel conversion.

Transparent Ultramicroelectrodes for Studying Interfacial Charge Transfer Kinetics of Photoelectrochemical Water Oxidation at TiO2 Nanorods with Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) has been extensively applied to high-throughput screening and quantification of the surface and interfaces of a photoelectrochemical (PEC) system. It is highly desirable to have a semiconductor photocatalytic electrode with well-defined geometry and active area comparable to the SECM’s tip electrode for accurately quantifying interfacial charge transfer activities and photoelectrochemically generated redox species of a photoelectrode. This is because the broadening effects due to mass transfer gradient and non-local electron transfer at a planar semiconductor surface can be minimized by utilizing the well-defined semiconductor substrate. Here, we present a newly developed platform as SECM substrate for investigating semiconductor PEC activities, which is based on a transparent ultramicroelectrode (UME) fabricated by using two-step photolithographic patterning and ion milling methods. This transparent UME with a 25 µm recessed disk shape is fully characterized with SECM for quantitatively understanding the interfacial electron transfer kinetics of IrCl6 2-/IrCl6 3- by comparing with theoretical results from finite element simulations in COMSOL Multiphysics. When coated with TiO2 nanorods as a model semiconductor material, the transparent UME can be used to quantify the catalytic PEC water oxidation in a feedback mode of SECM by sampling tip and substrate current signals simultaneously. This transparent UME-SECM study provides insights into the potential-dependent interfacial photogenerated charge transfer kinetics and quantitative analysis of photocurrent contributions from water oxidation and SECM tip-generated redox mediators. The transparent UME-SECM method can be potentially expanded to other SECM operation modes for understanding the dynamics of the surfaces and interfaces of a PEC catalyst.

Quantitative study of the kinetics of hydrogen evolution reaction on aluminum surface and the influence of chloride ion

The behaviors and kinetics of hydrogen evolution reaction (HER) on pure aluminum with passive film in the presence and absence of chloride ion are quantitatively investigated by using the tip generation/substrate collection mode of scanning electrochemical microscopy (SECM) with dual Al/Pt ultramicroelectrode (UME) as tip electrode and Pt UME as substrate electrode. The standard rate constants k0 and transfer coefficients αH of HER in ClO4−- and Cl−-containing solution are 6.9 × 10−7 cm/s and 0.22, 7.1 × 10−6 cm/s and 0.19, respectively. Results show that the kinetic of HER is slow and the destruction of Cl− on passive film can significantly promote the HER on Al surface. Moreover, these αH far less than commonly used 0.5 in corrosion research, can explain the great difference between theoretical Tafel slopes and experimental results. Besides, the existence of current plateau in Al electrode explains the large difference in corrosion potential during parallel testing.

Quantification of Surface Reactive Oxygen Species at Co-Modified BiVO4 with Surface Interrogation Mode of Scanning Electrochemical Microscopy

Our recent study suggests that cobalt modification can greatly improve the photoelectrochemical (PEC) water oxidation activities of n-BiVO4 (ACS Appl. Energy Mater., 1(5), 2283 (2018)). This enhancement is attributed to (1) the formation of a top layer of Co3O4 at BiVO4 surface as a cocatalyst and (2) the enrichment in electronic conductivity of BiVO4 upon Co doping. Here, surface interrogation mode of scanning electrochemical microscopy (SI-SECM) technique equipped with an ultramicroelectrode (UME) tip was employed to in-situ interrogate and quantify the surface adsorbed reactive oxygen species at Co-BiVO4 generated during PEC water oxidation. Experimental conditions of PEC water oxidation including applied potential and illumination time were found to play an important role in determining the surface coverage of the oxygen species. Their spontaneous decay under the open circuit condition was also characterized by increasing the time delay before interrogating the Co-BiVO4 surface.

Descriptive Role of Pt/PtOx Ratio on the Selective Chlorine Evolution Reaction under Polarity Reversal as Studied by Scanning Electrochemical Microscopy.

This study investigated competing chlorine evolution reaction (ClER) and oxygen evolution reaction (OER) on Pt electrodes under variable polarity reversal intervals (±16.7 mA cm-2, 30-600 s) in the context of distinctive roles of Pt(0) and PtOx on the surface in dilute (0.1 M) NaCl solutions. The substrate generation/tip collection mode of scanning electrochemical microscopy (SECM) quantified the current efficiency (CE) of ClER with a large tip-to-substrate distance (>500 μm) to avoid intervention of bubbles and spatial variations. Surface interrogation SECM using [Ru(NH3)6]2+/3+ coupled with X-ray photoelectron spectroscopy (XPS) identified the Pt4+-enriched surface of PtOx with a bilayer structure to give more efficient regeneration of Pt(0) under the shorter reversal interval. The in situ SECM complemented bulk electrolysis and XPS to demonstrate that ClER on Pt(0) and OER on PtOx primarily determine the CE of ClER, in agreement with a kinetic model. The descriptive role of surface Pt/PtOx ratio rationalized the enhanced selectivity for ClER upon the polarity switching, being independent on a scaling relationship. The current reversal (not allowed to IrO2 electrodes) also alleviated calcareous scale deposit in the electrolyte with hardness.

Steady‐State Electrocatalytic Activity Evaluation with the Redox Competition Mode of Scanning Electrochemical Microscopy: A Gold Probe and a Boron‐Doped Diamond Substrate

AbstractIn the current context of energetic transition, investigations of alternative complex systems require tools such as scanning electrochemical microscopy (SECM), offering interesting opportunities as an electroanalytical technique to evaluate innovative catalysts. Herein, we demonstrate how a judicious choice of probe and substrate materials opens up improved performances to achieve steady‐state measurements for oxygen reduction reaction (ORR) catalytic activity detection through redox competition scanning electrochemical microscopy (RC‐SECM). On the probe side, we show that using gold enhances the stability of the local oxygen concentration detection in comparison to the regularly used platinum one. On the substrate side, we evaluate boron‐doped diamond as an appealing alternative to classical support substrate, that shows a low ORR activity, high stability and very good reusability. This work introduces an alternative approach for quantitative measurements with SECM, improving measurement ease, comfort and reproducibility, thus paving the way towards standardized benchmarking and numerical simulation‐based parameter extraction.

Electrochemical detection of univalent Mg cation: A possible explanation for the negative difference effect during Mg anodic dissolution

Abstract Although the existence of short-lived univalent magnesium cation (Mg+) was supposed to play an important role on negative difference effect (NDE) during anodic dissolution of magnesium in previous work, no direct proof of the existence of Mg+ has ever been reported. Here, a modified substrate generation/tip collection mode of scanning electrochemical microscopy was applied to detect Mg+ via the reaction of generated Mg+ and potassium ferricyanide (K3[Fe(CN)6]). Based on the new design method and experimental data, our studies provide a direct evidence of the presence of Mg+ in aqueous solution combining with open circuit and polarization condition, which is benefit to understand NDE.

Numerical Deconvolution of Surface Interrogation Scanning Electrochemical Microscopy Experiments on Platinum During Hydrogen Evolution

AbstractIt is experimentally challenging to deconvolute the potential‐dependent adsorption of the different intermediates that occur during the hydrogen evolution reaction (HER) in alkaline media. This difficulty has limited our understanding regarding why the HER kinetics are more sluggish in alkaline media compared to acidic media. Herein, we utilized the surface interrogation mode of scanning electrochemical microscopy (SI‐SECM) to investigate the surface adsorbed species that form during the HER in alkaline media on polycrystalline platinum, Pt(poly). To deconvolute the different adsorbed intermediates, we developed a detailed COMSOL‐based kinetic model to rapidly simulate the SI‐SECM titration reactions under our experimental conditions. Utilization of this rapid‐kinetic model overcomes the limitation of SI‐SECM not having the ability to simultaneously resolve multiple surface adsorbed intermediates. We demonstrate that these numerical simulations can separate the potential dependant formation of the underpotential deposition of hydrogen (H(UPD)) from the overpotential deposition (H(OPD)) of hydrogen. In addition, our simulations show that a spectator species may also exist on the surface during HER potentials. Our simulations also show that at full H2‐producing potentials, the surface of Pt(poly) is fully saturated with intermediates. Comparison between the potential‐dependent adsorption of H(OPD) and Tafel analysis reveal that the Heyrovsky step is likely rate‐determining in alkaline media. However, in alkaline media the Heyrovsky step transitions from first‐order in H(OPD) at low H(OPD) coverage to zero‐order at high H(OPD) coverage, due to surface saturation of adsorbed intermediates. Tafel analysis in acidic media shows that the Heyrovsky step is likely rate‐determining, but remains first‐order in Had over a larger potential range. These fundamental insights reveal that a sluggish Heyrovsky step is a major contributor to the attenuated kinetics of the HER in alkaline media.

Scanning electrochemical microscopy for the investigation of redox potential of human myocardium-derived mesenchymal stem cells grown at 2D and 3D conditions

Three-dimensional (3D) cell cultivation systems in vitro are promising biomodels to study the metabolic processes of healthy and diseased human heart cells. Cardiac 3D-spheroids are mimicking cell living conditions and, therefore, they can be employed to investigate processes that occur in both extra-cellular and intra-cellular environments. In this study, human healthy and dilated left ventricle myocardium-derived mesenchymal stem cells (hmMSCs) were grown for 5 days in two different cell cultivation systems in vitro: (i) attached to the cell culture flask (2D-cultivation) and (ii) in spheres (3D-cultivation). Then 2D- and 3D-cultivated healthy and pathological hmMSCs have been investigated by generation-collection mode of scanning electrochemical microscopy (GC-SECM) using 2-methylnaphthalene-1,4-dione (menadione or MD) as a redox mediator. Healthy 2D-cultivated hmMSCs were more redox active, therefore, faster responded to MD and were more sensitive to the high MD concentrations compared to the pathological hmMSCs. 3D-cultivation of pathological cells improved their redox activity and made healthy hmMSCs more resistant to the MD. Data of this study show that SECM measurements, using redox mediator MD, can be applied to investigate changes of intra-cellular redox status of human healthy and dilated hmMSCs grown under different conditions. Moreover, the intra-cellular redox status of dilated hmMSCs can be purposefully improved by 3D-cultivation with further their application for therapeutic purposes.

Electrocatalytic Metallic Nanostructures Prepared By Electrorefining and Cathodic Corrosion

Metallic nanostructures (NS) due to their unique properties are often used as electrocatalytic electrode materials in energy conversion and storage as well as in sensing applications. Their common methods of preparation involve homogeneous synthesis and electrodeposition from solutions containing appropriate precursor and often reducing agent and capping agent (surfactant). The main drawbacks of these methods are restricted yield, waste production and often intrinsic contamination of the surface of obtained NS. Moreover, surface capping ligands affect electrocatalytic activity by hindrance of reactant access to the active sites.We propose a versatile method of preparation of bare (non-capped) mono- and multi-metallic (Au,1 Cu,2 Ag, Fe) NS by localized electrorefining of polycrystalline raw metals at high efficiency in a controlled manner. Catalytic activities of obtained NS towards oxygen reduction reaction (ORR) in alkaline media, hydrogen evolution (HER) and carbon dioxide reduction (CO2RR) to easily electrooxidizable fuels (formic acid and carbon monooxide) were analyzed by feedback mode scanning electrochemical microscopy (SECM). The morphology and specific activity of obtained NS depend on used support material (indium tin oxide (ITO) and glassy carbon) and other electrorefining parameters such as electrodeposition potential, source velocity and the composition of the electrolyte. The last parameter determines stoichiometry of Faradaic processes. Both gold and copper electrooxidation and electroreduction can follow one electron stoichiometry. ORR in alkaline media and CO2RR occur effectively on NS with highly developed surfaces, containing large number of defects, corners and edges, whereas HER occurs efficiently at crystallographic Cu facets. Bare gold NS also exhibit outstanding plasmonic properties. They were applied as support for surface-enhanced Raman spectroscopy (SERS) of single molecules providing enhancement factor >106.1 Another method of preparation of metallic nanostructures is cathodic corrosion. This approach for platinum was studied by Koper group.3 We used this procedure for platinum ultramicroelectrode treatment. Obtained Pt NS exhibit unique catalytic properties towards electrooxidation of glucose.

Coulometric Titration of Active Sites at Mesostructured Cobalt Oxide Spinel by Surface Interrogation Mode of Scanning Electrochemical Microscopy

Cobalt-based transition-metal oxides are promising candidates for the oxygen evolution reaction (OER). However, a complex interplay between the catalyst crystal structures and material morphologies...

Scanning Electrochemical Microscopy of Electrically Heated Wire Substrates

We report a new configuration for enhancing the performance of scanning electrochemical microscopy (SECM) via heating of the substrate electrode. A flattened Pt microwire was employed as the substrate electrode. The substrate was heated by an alternating current (AC), resulting in an increased mass transfer between the wire surface and the bulk solution. The electrochemical response of the Pt wire during heating was investigated by means of cyclic voltammetry (CV). The open circuit potential (OCP) of the wire was recorded over time, while varied heating currents were applied to investigate the time needed for establishing steady-state conditions. Diffusion layer studies were carried out by performing probe approach curves (PACs) for various measuring modes of SECM. Finally, imaging studies of a heated substrate electrode surface, applying feedback, substrate generation/tip collection (SG/TC), and the competition mode of SECM, were performed and compared with room temperature results.

Screening and characterization of bimetallic Pt–M (M = Y, La, Ce, Pr, Nd, Gd) electrocatalysts for the oxygen reduction reaction

In this study bimetallic platinum–metal (Pt–M; M = Y, La, Ce, Pr, Nd, Gd) electrocatalyst arrays were fabricated through a combinational method using a dispensing system. These Pt-based electrocatalyst arrays were then rapidly screened for their suitability for the oxygen reduction reaction (ORR) by using the tip generation–substrate collection mode of scanning electrochemical microscopy; O2 was generated at the tip and it was reduced at spots of the electrocatalyst on the substrate. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractometry were employed to analyze the surface morphologies, elemental compositions, and crystallinities of the electrocatalysts. Tip/substrate voltammetry, approach curve analysis, and rotating disk electrode analysis were used to examine the kinetics of the potential electrocatalysts for the ORR. Among the prepared electrocatalysts, a spot having the composition Pt7Y3 provided the highest current in 0.01 M H2SO4/0.1 M Na2SO4. The Pt7Y3 electrocatalyst exhibited excellent electrocatalytic activity toward the ORR, with a Tafel slope of 123 mV, a rate constant of 0.023 cm/s, and a transfer coefficient of 0.47. The electron transfer numbers of the binary Pt-based electrocatalysts were all close to 4, indicating that their mechanisms of oxygen reduction followed the four-electron reduction pathway. Furthermore, the percentage of H2O2 produced during the ORR on the Pt7Y3 electrocatalyst was the lowest among these tested systems, with a value of less than 2%.

Catalytic Water Oxidation Reaction at Nanostructured Titania Modified with Carbonized Metal Organic Framework

Solar energy can be used for direct water splitting to produce hydrogen through a photoelectrochemical (PEC) reaction at semiconducting electrodes. Thus, the overall efficiency of the PEC system is dependent on electrocatalytic or photoelectrocatalytic electrode materials for efficient light absorption, charge separation and transport, in proton reduction and water oxidation half reactions. Herein, a new hybrid catalytic electrode comprised of NH2-MIL-125, a titanium-based metal organic framework (MOF), derived nanostructured Titania electrode material. XRD, SEM and EDX characterizations suggest that nanostructured Titania-MOF electrode is comprised of an underlying layer of TiO2nanorods and the upper layer of distributed clusters of MOF derived disk-shaped nanoparticles (NPs) with an island morphology. The NH2-MIL-125 NPs are formed through a colloid seed-assisted solvothermal reaction and afterwards carbonized while clustering during a pyrolysis process. The resulting nanostructure proved to be composed of C, O, N, and Ti elements. The Titania was employed as the anode substrate of the MOF NPs because it exhibits significantly improved activity for water oxidation and this reaction is greatly enhanced upon coating with carbonized MOF structure. The surface interrogation mode of scanning electrochemical microscopy (SI-SECM) is applied in this study to investigate reactive surface states (RSSs) on the nanostructured electrodes, owing to its selectivity to surface species, capability to in situ quantify for both surface coverage and reactivity of adsorbed RSSs, and usefulness to obtain spatially and temporally-resolved information.

The local electrochemical behavior of the AA2098‐T351 and surface preparation effects investigated by scanning electrochemical microscopy

In this work, scanning electrochemical microscopy (SECM) measurements were employed to characterize the electrochemical activities on polished and as‐received surfaces of the 2098‐T351 aluminum alloy (AA2098‐T351). The effects of the near surface deformed layer (NSDL) and its removal by polishing on the electrochemical activities of the alloy surface were evaluated and compared by the use of different modes of SECM. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were also employed to characterize the morphology of the surfaces. The surface chemistry was analyzed by X‐ray photoelectron spectroscopy (XPS). The surface generation/tip collection (SG/TC) and competition modes of the SECM were used to study hydrogen gas (H2) evolution and oxygen reduction reactions, respectively. H2 evolution and oxygen reduction were more pronounced on the polished surfaces. The feedback mode of SECM was adopted to characterize the electrochemical activity of the polished surface that was previously corroded by immersion in a chloride‐containing solution, in order to investigate the influence of the products formed on the active/passive domains. The precorroded surface and as‐received surfaces revealed lower electrochemical activities compared with the polished surface showing that either the NSDL or corrosion products largely decreased the local electrochemical activities at the AA2098‐T351 surfaces.

Nanoscale Intelligent Imaging Based on Real-Time Analysis of Approach Curve by Scanning Electrochemical Microscopy.

Scanning electrochemical microscopy (SECM) enables high-resolution imaging by examining the amperometric response of an ultramicroelectrode tip near a substrate. Spatial resolution, however, is compromised for nonflat substrates, where distances from a tip far exceed the tip size to avoid artifacts caused by the tip-substrate contact. Herein, we propose a new imaging mode of SECM based on real-time analysis of the approach curve to actively control nanoscale tip-substrate distances without contact. The power of this software-based method is demonstrated by imaging an insulating substrate with step edges using standard instrumentation without combination of another method for distance measurement, e.g., atomic force microscopy. An ∼500 nm diameter Pt tip approaches down to ∼50 nm from upper and lower terraces of a 500 nm height step edge, which are located by real-time theoretical fitting of an experimental approach curve to ensure the lack of electrochemical reactivity. The tip approach to the step edge can be terminated at <20 nm prior to the tip-substrate contact as soon as the theory deviates from the tip current, which is analyzed numerically afterward to locate the inert edge. The advantageous local adjustment of tip height and tip current at the final point of tip approach distinguishes the proposed imaging mode from other modes based on standard instrumentation. In addition, the glass sheath of the Pt tip is thinned to ∼150 nm to rarely contact the step edge, which is unavoidable and instantaneously detected as an abrupt change in the slope of approach curve to prevent damage of the fragile nanotip.

Interrogating the Surface Intermediates and Water Oxidation Products of Boron‐Doped Diamond Electrodes with Scanning Electrochemical Microscopy

AbstractBoron‐doped diamond (BDD) electrodes are widely used in electrochemical sensing and water purification owing to their chemical and structural stability under harsh reaction conditions. Water oxidation at BDD electrodes is known to produce reactive oxygen species, but the discharged and surface chemistries involved in these processes have not been studied in depth. Here, we present scanning electrochemical microscopy (SECM) studies of electrogenerated intermediates and products formed on sp2 carbon‐containing BDD electrodes that display stark differences in their reactivity as a function of electrolyte type and pH during water oxidation. The most reactive and abundant species discharged from the electrode were observed at pH 11 in sulfate electrolyte. With the surface interrogation mode of SECM, two kinetically distinct surface intermediates were clearly distinguished, with one forming two orders of magnitude faster than the other but displaying a slower desorption rate. The surface coverage of these species was estimated in the range of 4–7×10−5 mol/cm2 for the first, and 3–4.4×10−5 mol/cm2 for the second one. SECM imaging suggested that regions of increased product evolution have decreased electron transfer kinetics and limited surface sites for intermediate binding. This work establishes methods for studying highly reactive intermediates found in BDD and paves the way for the inspection of other interfaces where solvolysis impacts their reactivity and evolution.

Potentiometric Tip Electrodes for Improved Visualization of Galvanic Corrosion Processes Using SECM

Galvanic corrosion of magnesium is one of the main reasons of the limited usage of this metal. Therefore the galvanic corrosion of magnesium is of great scientific and industrial interest. Among many analytical methods being used, Scanning Electrochemical Microscopy (SECM) has the advantage of chemical surface imaging with high spatial and temporal resolution. When it comes to Mg corrosion, the amperometric mode of SECM is an attractive option although Mg ions cannot be measured directly due to the high negative overvoltage of Mg2+ reduction. Instead, the feedback mode and hydrogen detection in sample generator – tip collector mode are employed [1]. However, H2 oxidation is not a diffusion controlled process and local ion concentrations may affect the oxidation current. Alternately, SECM can be employed in potentiometric mode. In this case, the sensing probe is an ion selective microelectrode (ISME) which potential is measured against a reference electrode using an operational amplifier-based voltage follower. In this way, direct measurement of Mg2+ distribution has been achieved [2]. However, the occurrence of electric field effects for Mg corroding under galvanic coupling has been demonstrated [3]. Electric cross-talk shifts the measured potentials with respect to the calibration completed in unbiased conditions, resulting in the determination of wrong ion activities. The work reported here demonstrates the applicability of ion selective electrodes in multibarreled arrangement for simultaneous monitoring of pH and Mg2+ distribution above AZ63 magnesium alloy using SECM. The superior performance of multibarreled tips containing an internal reference electrode compared to “traditional’ single barreled electrodes and double barreled electrodes is shown.

Micropatterning of Metals by Tip Electrode Dissolution and Imaging of Oxygen Reduction Reaction Using Scanning Electrochemical Microscopy

Surface patterning on substrate has been applied to various nano-devices, microfluidics, cell biology, microelectrochemical systems, and electronics. Most strategies have been based on lithography, but despite the many advantages of conventional lithography, its complex procedures, facilities and high cost arouse desire for the alternative technique. The major complexity in lithography is due to the indirect patterning which uses mask as a template and results in multi-step process. Meanwhile, electrochemical patternings have been also carried out for patterning of metals, and especially maskless patternings are possible using scanning electrochemical microscopy (SECM). We have electrodeposited palladium and gold micropatternings using SECM with the metal precursor ions generated via anodic dissolution of the ultramicroelectrode (UME) tip itself. Simultaneously, in‐situ reduction of the metal ions occurred at the substrate electrode. Contrary to general electrodeposition methods where metal precursor ions exist in the entire solution, in case of local deposition, the metal ions were supplied only from the anodic dissolution of the tip electrode composed of the identical metal which was positioned in a close proximity to the substrate. Therefore, the ions generated from the tip can be reduced only on nearby substrate, not on the entire conductive surface. Especially, this is the first study on the local deposition of Pd using direct Pd dissolution. The catalytic activities of oxygen reduction on the Pd or Au patterns were investigated simultaneously but separately with tip generation‐substrate collection mode of SECM and the activities of each metal deposit varied with potentials applied on substrate. This local deposition technique using SECM could be also applied to other metals if the metal dissolution is possible in proper electrolyte solution within water-stable potential window. Figure 1

Systematic Analysis of Different Cell Spheroids with a Microfluidic Device Using Scanning Electrochemical Microscopy and Gene Expression Profiling.

The 3D cell spheroid is an emerging tool that allows better recapitulating of in vivo scenarios with multiple factors such as tissue-like morphology and membrane protein expression that intimately coordinates with enzyme activity, thus providing a psychological environment for tumorigenesis study. For analyzing different spheroids, conventional optical imaging may be hampered by the need for fluorescent labeling, which could cause toxicity side effects. As an alternative approach, scanning electrochemical microscopy (SECM) enables label-free imaging. However, SECM for cell spheroid imaging is currently suffering from incapability of systematically analyzing the cell aggregates from spheroid generation, electrochemical signal gaining, and the gene expression on different individual cell spheroids. Herein, we developed a top-removable microfluidic device for cell aggregate yielding and SECM imaging methodology to analyze heterotypic 3D cell spheroids on a single device. This technique allows not only on-chip culturing of cell aggregates but also SECM imaging of the spheroids after opening the chip and subsequent qPCR assay of corresponding clusters. Through employment of the micropit arrays (85 × 4) with a top withdrawable microfluidic layer, uniformly sized breast tumor cell and fibroblast spheroids can be simultaneously produced on a single device. By leveraging voltage-switching mode SECM at different potentials of dual mediators, we evaluated alkaline phosphatase without disturbance of substrate morphology for distinguishing the tumor aggregates from stroma. Moreover, this method also enables gene expression profiling on individual tumor or stromal spheroids. Therefore, this new strategy can seamlessly bridge SECM measurements and molecular biological analysis.