Electrochemical Reactions
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Koushik Barman ◽  
Xiang Wang ◽  
Rui Jia ◽  
Gaukhar Askarova ◽  
Guoxiang Hu ◽  

2021 ◽  
Mark Aarts ◽  
Alain Reiser ◽  
Ralph Spolenak ◽  
Esther Alarcon-Llado

Regulating the state of the solid-liquid interface by means of electric fields is a powerful tool to control electrochemistry. In scanning probe systems, this can be confined closely to a scanning (nano)electrode by means of fast potential pulses, providing a way to probe the interface and control electrochemical reactions locally, as has been demonstrated in nanoscale electrochemical etching. For this purpose, it is important to know the spatial extent of the interaction between pulses applied to the tip, and the substrate. In this paper we use a framework of diffuse layer charging to describe the localization of electrical double layer charging in response to a potential pulse at the probe. Our findings are in good agreement to literature values obtained in electrochemical etching. We show that the pulse can be much more localized by limiting the diffusivity of the ions present in solution, by confined electrodeposition of cobalt in a dimethyl sulfoxide solution, using an electrochemical scanning tunneling microscope. Finally, we demonstrate the deposition of cobalt nanostructures (<100 nm) using this method. The presented framework therefore provides a general route for predicting and controlling the time-dependent region of interaction between an electrochemical scanning probe and the surface.

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5877
Dessalegn Ahmed Yeshanew ◽  
Moera Gutu Jiru ◽  
Gulam Mohammed Sayeed Ahmed ◽  
Irfan Anjum Badruddin ◽  
Manzoore Elahi M. Soudagar ◽  

Water pipe surface deterioration is the result of continuous electrochemical reactions attacking the surface due to the interaction of the pipe surface with environments through the time function. The study presents corrosion characterization at the surface and sub-surface of damaged ductile iron pipe (DIP) and galvanized steel (GS) pipes which served for more than 40 and 20 years, respectively. The samples were obtained from Addis Ababa city water distribution system for the analysis of corrosion morphology patterns at different surface layers. Mountains 8.2 surface analysis software was utilized based on the ISO 25178-2 watershed segmentation method to investigate corrosion features of damaged pipe surface and to evaluate maximum pit depth, area, and volume in-situ condition. Based on the analysis maximum values of pit depth, area and volume were 380 m, 4000 m2, and 200,000 m3, respectively, after 25% loss of the original 8 mm thickness of DIP. Similarly, the pit depth of the GS pipe was 390 whereas the maximum pit area and volume are 4000 m2 and 16,000 m3, respectively. In addition, characterizations of new pipes were evaluated to study microstructures by using an optical microscope (OM), and a scanning electron microscope (SEM) was used to analyze corrosion morphologies. Based on the SEM analysis, cracks were observed at the sub-surface layer of the pipes. The results show that uniform corrosion attacked the external pipe surface whereas pitting corrosion damaged the subsurface of pipes. The output of this study will be utilized by water suppliers and industries to investigate corrosion phenomena at any damage stage.

Liu Yang ◽  
Chenxi Cao ◽  
Quanquan Gan ◽  
Hao Pei ◽  
Qi Zhang ◽  

We propose a dynamic proton exchange membrane fuel cell model for cold start simulation in account for reactant transport, water phase-transfer and electrochemical reactions within catalyst agglomerates. The competition between in-agglomerate concentration loss and coverage of active electrocatalytic surface is shown to create different failure modes for low and high start-up currents. The critical ice fraction of failure was studied for different catalyst layer (CL) thickness and ionomer to carbon ratios (I/C) at 0.4 A cm-2. Thicker cathode CLs allow cold start to proceed with higher ice fractions. In contrast, larger cathode I/Cs causes cold-start failure at lower ice fractions because of reduction of the CL porosity and agglomerate pore sizes that significantly increases the oxygen transport resistance. By utilizing the electro-osmotic drag effect, slightly thick anode CL could act as effective heat sources during cold start at high currents with minimal impact on the nominal cell performance.

2021 ◽  
pp. 2105480
Chunlong Dai ◽  
Linyu Hu ◽  
Xuting Jin ◽  
Hao Chen ◽  
Xinqun Zhang ◽  

2021 ◽  
Yongjun Zheng ◽  
Hong Yang ◽  
Lufang Zhao ◽  
Yuhan Bai ◽  
Xinghua Chen ◽  

By virtue of near-zero optical background and photobleaching, electrochemiluminescence (ECL), an optical phenomenon excited by electrochemical reactions, has drawn extensive attention in both fundamental studies and wide applications especially of ultrasensitive bioassay. Developing diverse ECL emitters is crucial to unlock their multiformity and performances, but remains a formidable challenge, due to the rigorous requirements for ECL. Herein, we report a general intramolecular ECL resonance energy transfer (iECL-RET) strategy to light up ECL-inactive dyes in aqueous solutions using an existing high-performance ECL initiators. As a proof-of-concept, a series of luminol donor-dye acceptor based ECL emitters with near unity RET efficiency and coarse/fine tunable emission wavelengths were demonstrated. Different to previous exploitation of new molecule single-handedly to address all the prerequisites of ECL, each unit in the proposed ECL ensemble performed maximally its own functions. The iECL-RET strategy would greatly expand the family members of ECL emitters for more demanding future applications.

2021 ◽  
Vol 9 ◽  
Adaly Garcia ◽  
Kinsley Wang ◽  
Fatima Bedier ◽  
Miriam Benavides ◽  
Zijian Wan ◽  

Prussian blue is an iron-cyanide-based pigment steadily becoming a widely used electrochemical sensor in detecting hydrogen peroxide at low concentration levels. Prussian blue nanoparticles (PBNPs) have been extensively studied using traditional ensemble methods, which only provide averaged information. Investigating PBNPs at a single entity level is paramount for correlating the electrochemical activities to particle structures and will shed light on the major factors governing the catalyst activity of these nanoparticles. Here we report on using plasmonic electrochemical microscopy (PEM) to study the electrochemistry of PBNPs at the individual nanoparticle level. First, two types of PBNPs were synthesized; type I synthesized with double precursors method and type II synthesized with polyvinylpyrrolidone (PVP) assisted single precursor method. Second, both PBNPs types were compared on their electrochemical reduction to form Prussian white, and the effect from the different particle structures was investigated. Type I PBNPs provided better PEM sensitivity and were used to study the catalytic reduction of hydrogen peroxide. Progressively decreasing plasmonic signals with respect to increasing hydrogen peroxide concentration were observed, demonstrating the capability of sensing hydrogen peroxide at a single nanoparticle level utilizing this optical imaging technique.

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1068
Javier Meléndez-Campos ◽  
Matias Vázquez-Piñón ◽  
Sergio Camacho-Leon

Dielectric characteristics are useful to determine crucial properties of liquids and to differentiate between liquid samples with similar physical characteristics. Liquid recognition has found applications in a broad variety of fields, including healthcare, food science, and quality inspection, among others. This work demonstrates the fabrication, instrumentation, and functionality of a portable wireless sensor node for the permittivity measurement of liquids that require characterization and differentiation. The node incorporates an interdigitated microelectrode array as a transducer and a microcontroller unit with radio communication electronics for data processing and transmission, which enable a wide variety of stand-alone applications. A laser-ablation-based microfabrication technique is applied to fabricate the microelectromechanical systems (MEMS) transducer on a printed circuit board (PCB) substrate. The surface of the transducer is covered with a thin layer of SU-8 polymer by spin coating, which prevents it from direct contact with the Cu electrodes and the liquid sample. This helps to enhance durability, avoid electrode corrosion and contamination of the liquid sample, and to prevent undesirable electrochemical reactions to arise. The transducer’s impedance was modeled as a Randles cell, having resistive and reactive components determined analytically using a square wave as stimuli, and a resistor as a current-to-voltage converter. To characterize the node sensitivity under different conditions, three different transducer designs were fabricated and tested for four different fluids, i.e., air, isopropanol, glycerin, and distilled water—achieving a sensitivity of 1.6965 +/− 0.2028 εr/pF. The use of laser ablation allowed the reduction of the transducer footprint while maintaining its sensitivity within an adequate value for the targeted applications.

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