Preparation, Applications, and Digital Simulation of Carbon Interdigitated Array Electrodes

Automated Measurement of Electrogenerated Redox Species Degradation Using Multiplexed Interdigitated Electrode Arrays

Characterizing the decomposition of electrogenerated species in solution is essential for applications involving electrosynthesis, homogeneous electrocatalysis, and energy storage with redox flow batteries. In this work, we present an automated, multiplexed, and highly robust platform for determining the rate constant of chemical reaction steps following electron transfer, known as the EC mechanism. We developed a generation-collection methodology based on microfabricated interdigitated electrode arrays (IDAs) with variable gap widths on a single device. Using a combination of finite-element simulations and statistical analysis of experimental data, our results show that the natural logarithm of collection efficiency is linear with respect to gap width, and this quantitative analysis is used to determine the decomposition rate constant of the electrogenerated species (k _c). The integrated IDA method is used in a series of experiments to measure k _c values between ∼0.01 and 100 s^-1 in aqueous and nonaqueous solvents and at concentrations as high as 0.5 M of the redox-active species, conditions that are challenging to address using standard methods based on conventional macroelectrodes. The versatility of our approach allows for characterization of a wide range of reactions including intermolecular cyclization, hydrolysis, and the decomposition of candidate molecules for redox flow batteries at variable concentration and water content. Overall, this new experimental platform presents a straightforward automated method to assess the degradation of redox species in solution with sufficient flexibility to enable high-throughput workflows.

Micro and Nano Interdigitated Electrode Array (IDEA)-Based MEMS/NEMS as Electrochemical Transducers: A Review

Micro and nano interdigitated electrode array (µ/n-IDEA) configurations are prominent working electrodes in the fabrication of electrochemical sensors/biosensors, as their design benefits sensor achievement. This paper reviews µ/n-IDEA as working electrodes in four-electrode electrochemical sensors in terms of two-dimensional (2D) planar IDEA and three-dimensional (3D) IDEA configurations using carbon or metal as the starting materials. In this regard, the enhancement of IDEAs-based biosensors focuses on controlling the width and gap measurements between the adjacent fingers and increases the IDEA's height. Several distinctive methods used to expand the surface area of 3D IDEAs, such as a unique 3D IDEA design, integration of mesh, microchannel, vertically aligned carbon nanotubes (VACNT), and nanoparticles, are demonstrated and discussed. More notably, the conventional four-electrode system, consisting of reference and counter electrodes will be compared to the highly novel two-electrode system that adopts IDEA's shape. Compared to the 2D planar IDEA, the expansion of the surface area in 3D IDEAs demonstrated significant changes in the performance of electrochemical sensors. Furthermore, the challenges faced by current IDEAs-based electrochemical biosensors and their potential solutions for future directions are presented herein.

Photoelectrochemical oxygen evolution with interdigitated array electrodes: the example of TiO2

The catalytic reactions of photoelectrochemical water splitting attracts tremendous attention as a promising strategy for clean energy production. And the research on reaction mechanism is particularly important in design and developing new catalysts. In this work, the special electrochemical tool of interdigitated array (IDA) electrodes was utilized in investigating the photoelectrochemical oxygen evolution reaction process and detecting the reaction productin situwith the generation-collection mode. TiO₂was taken as a model catalyst and was decorated onto the IDA generator electrode through an electrophoresis method, so that the photoelectrochemical water splitting can take place on the IDA generator and the reaction product can be detected directly with the IDA collector in real time. It is found that TiO₂can be successfully decorated onto the surface of IDA electrode with the expected photoelectrochemical activity, and the generation-collection mode reveals and distinguishes the production of O₂from the overall photoelectrochemical current on TiO₂generator. The mass transfer process of O₂from the TiO₂generator to the collector could be observed as well. Large overall current at high potential range indicates the possible increasing production of the byproducts or nonfaradaic current.

The real-time investigation of the nickel-iron hydroxide catalyzed oxygen evolution reaction with interdigitated array electrodes

Electrocatalysis of oxygen evolution reaction (OER), one of the most important members in clean and efficient energy conversion, requires increasing studies on reaction process analysis, catalyst investigation and evaluation and so on throughin situexperiments. The bottleneck is the difficulties on clear and precise understanding towards the multi-step reactions with fast reaction rates. Interdigitated array (IDA) electrodes with sensitive responses on the generation, transfer and collection of reaction products are proposed and utilized as a convenient and effective tool toin situmonitor and characterize the reaction thermodynamics and kinetics information. Herein, nickel-iron hydroxide, a promising and novel OER catalyst, is chosen as the candidate to demonstrate the merit of IDA on studying the OER. With the generator-collector mode, the real-time oxygen evolution process is monitored precisely with the IDA collector, distinguished it from the general catalytic current which is normally recorded with conventional electrochemical method. In another word, the actual faradaic efficiency was observed experimentally with IDA electrodes, which is often misled as 100% in many works. The diffusion of the reaction products has been 'seen' as well with the generator-collector mode. This general tool (IDA) may make more contributions on the study of reaction process of all electrocatalytical reactions.

Microfabricated electrochemical sensing devices

Electrochemistry provides possibilities to realize smart microdevices of the next generation with high functionalities. Electrodes, which constitute major components of electrochemical devices, can be formed by various microfabrication techniques, and integration of the same (or different) components for that purpose is not difficult. Merging this technique with microfluidics can further expand the areas of application of the resultant devices. To augment the development of next generation devices, it will be beneficial to review recent technological trends in this field and clarify the directions required for moving forward. Even when limiting the discussion to electrochemical microdevices, a variety of useful techniques should be considered. Therefore, in this review, we attempted to provide an overview of all relevant techniques in this context in the hope that it can provide useful comprehensive information.

An interdigitated electrode with dense carbon nanotube forests on conductive supports for electrochemical biosensors

A highly sensitive interdigitated electrode (IDE) with vertically aligned dense carbon nanotube forests directly grown on conductive supports was demonstrated by combining UV lithography and a low temperature chemical vapor deposition process (470 °C). The cyclic voltammetry (CV) measurements of K4[Fe(CN)6] showed that the redox current of the IDE with CNT forests (CNTF-IDE) reached the steady state much more quickly compared to that of conventional gold IDE (Au-IDE). The performance of the CNTF-IDE largely depended on the geometry of the electrodes (e.g. width and gap). With the optimum three-dimensional electrode structure, the anodic current was amplified by a factor of ∼18 and ∼67 in the CV and the chronoamperometry measurements, respectively. The collection efficiency, defined as the ratio of the cathodic current to the anodic current at steady state, was improved up to 97.3%. The selective detection of dopamine (DA) under the coexistence of l-ascorbic acid with high concentration (100 μM) was achieved with a linear range of 100 nM-100 μM, a sensitivity of 14.3 mA mol-1 L, and a limit of detection (LOD, S/N = 3) of 42 nM. Compared to the conventional carbon electrodes, the CNTF-IDE showed superior anti-fouling property, which is of significant importance for practical applications, with a negligible shift of the half-wave potential (ΔE1/2 < 1.4 mV) for repeated CV measurements of DA at high concentration (100 μM).