Figure - available from: Frontiers in Chemistry
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(A) Schematic of the scanning bipolar cell (SBC) and components. (B) To-scale axisymmetric geometry used in finite element method simulations when H = 2ri with key features and current pathways emphasized. (C) Equivalent circuit approximating current flow pathways through the SBC.
Source publication
Bipolar electrochemistry involves spatial separation of charge balanced reduction and oxidation reactions on an electrically floating electrode, a result of intricate coupling of the work piece with the ohmic drop in the electrochemical cell and to the thermodynamics and kinetics of the respective bipolar reactions. When paired with a rastering mic...
Citations
Bipolar electrochemistry (BPE) is a technique that involves two opposite chemical processes, namely an oxidation and a reduction, occurring simultaneously on the surface of a conducting object, usually without connection to a power supply. The basic phenomenon has already been described and used for many decades but regained a lot of interest in recent years, thanks to several attractive features for developing new applications in various areas ranging from materials science and analytical chemistry to catalysis and even life science. Consequently, BPE has experienced a substantial growth in the number of users and publications. This is mostly due to several advantages over classic electrochemistry, such as the absence of an ohmic contact, the generation of a directional gradient of electroactivity on the object, and the possibility to address simultaneously thousands of objects, which opens the door for high‐throughput screening of (electro)chemical properties. Also, some features of this “wireless” electrochemistry allow performing experiments that cannot be achieved with a classic electrochemical setup. Last but not least, only rather low‐cost equipment is needed.
The objective of the present contribution is to introduce first some fundamental aspects of BPE, and then to illustrate its different developments, highlighting not only the historic landmark achievements, but also the most recent findings, especially in the context of micro‐ and nanoscience. This article illustrates the singularities and advantages of this straightforward approach and hopefully convinces the reader of the power of this interesting electrochemical concept.
A novel micro-nano-structured Cr3C2–NiCr cermet coating was prepared on 316L stainless steel by high-velocity oxygen fuel spraying technology (HVOF). Cermet coatings with different contents of micro-and nano-sized Cr3C2 particles as the hard phase and a NiCr alloy matrix as the bonding phase were prepared and characterized in terms of porosity, microhardness, and corrosive wear resistance in a 3.5% NaCl solution and artificial seawater. Compared to nanostructured coatings, micro-nano-structured coatings avoid decarburization and reduce nanoparticle agglomeration during the spray process, and mechanical and electrochemical properties were improved in comparison with those of conventional coatings. The micro-nano-structured Cr3C2–NiCr coating rendered low porosity (≤0.34%) and high microhardness (≥1105.0HV0.3). The coating comprising 50% nano-sized Cr3C2 grains exhibited the best corrosive wear resistance owing to its densest microstructure and highest microhardness. Furthermore, compared to static corrosion, the dynamic corrosion of the coatings led to more severe mechanical wear, because corrosion destroyed the coating surface and ions promoted corrosion to invade coatings through the pores during corrosion wear.
The Scanning Bipolar Electrochemical Microscope (SBECM) allows precise positioning of an electrochemical micro-probe serving as bipolar electrode that can be wirelessly interrogated by coupling the electrochemical detection reaction with an electrochemiluminescent reporting process. As a result, the spatially heterogeneous concentrations of an analyte of interest can be converted in real time into a map of sample reactivity. However, this can only be achieved upon optimization of the analytical performance ensuring adequate sensitivity. Here, we present the evaluation and optimized operation of the SBECM for the detection of small changes in local O2 concentrations. Parameters for achieving an improved sensitivity as well as possibilities for improving the signal-to-noise ratio in the optical signal readout are evaluated. The capability of the SBECM for O2 detection is shown at controlled conditions by recording the topography of a patterned sample and monitoring O2 evolution from a photoelectrocatalyst material.
