Micro-strip electrode

A test reactor was made of stainless steel which contains a so-called micro-strip electrode array [75]. This array is composed of thin strips surrounded by larger objects. The anodes are thin gold strips evaporated on glass bulk. The cathodes have a more complex bulky pattern similar to an oval. 

Reactor type Micro-strip electrode reactor Cathode width 500 pm... 

GP 1] [R 13] So-called micro-strip electrodes (MSE) can act as electrically steerable catalysts when used to switch on and off the conversion of ammonia at moderate voltages, several hundred volts (6 vol.-% NHj, 88 vol.-% O2, balance He 0.51 ms 260-380 °C) [75]. Thereby, NO formation was observed. By emitting and accelerating electrons in the range of mA cm current density from the solid to the gas phase, radicals were formed, typically much more than the number of released electrons, e.g. 10 radicals per electron. This efficient use of energy is referred to as dynamic catalysis. The gas phase near the electrodes contains hot and cold radicals, thus providing a two-temperature system. 

Gun, I., Salaun, P. and van den Berg, C. M. G. (2006), Advantages of using a mercury coated, micro-wire, electrode in adsorptive cathodic stripping voltammetry. Anal. Chim. Acta, 571(1) 86-92. 

Bismuth-film electrodes (BiFEs), consisting of a thin bismuth-film deposited on a suitable substrate, have been shown to offer comparable performance to MFEs in ASY heavy metals determination [17]. The remarkable stripping performance of BiFE can be due to the binary and multi-component fusing alloys formation of bismuth with metals like lead and cadmium [18]. Besides the attractive characteristics of BiFE, the low toxicity of bismuth makes it an alternative material to mercury in terms of trace-metal determination. Various substrates for bismuth-film formation are reported. Bismuth film was prepared by electrodeposition onto the micro disc by applying an in situ electroplating procedure [19]. Bismuth deposition onto gold [20], carbon paste [21], or glassy carbon [22-24] electrodes have been reported to display an... 

The best configuration of ensembles of microelectrodes is a collection of micro discs of equal size, arranged on a uniform grid, at equal distances from each other. Sometimes this is not feasible, and ensembles containing electrodes of nonuniform size and/or distance have been considered. Ensembles of strip microelectrodes have also been constructed, and the variation of current with time for such configurations has been evaluated. 

Copper has been measured in soil using a portable electroanalytical device based on stripping voltammetry. In marine chemistry, sediments have been sampled and analysed in real-time by in situ solid-state voltammetric micro-electrodes. The analyser was used to examine levels of various redox species and trace metals, e.g. iron and manganese, in salt marsh sediments and other matrices. 

Another difference between classical electrochemistry and electrochemical engineering lies in the size of the electrode. Conventional electrochemistry most commonly employs micro electrodes of well defined area operating under carefully controlled current and mass transfer conditions. Conversely, electrochemical engineering typically employs large surface area electrodes, where, moreover, the surface area and electrode activity varies constantly as metal is deposited. In addition, there are usually difficulties in maintaining uniform potential control and current distribution over the electrode surface. It is also necessary to consider the reverse stripping process of recovering the metal after collection. 

The electrochemical sensors with chemical recognition applied to pesticides analyses take advantage of the analytical features of the differential pulse voltammetry, square-wave voltammetry, and stripping voltammetry [26-30], which allow pesticides detection at residues levels. Current efforts are directed toward sensitivity and selectivity improvement by chemical modification of the electrode surface by molecularly imprinted polymers and micro- and nanostructured materials [31]. 

In two dimensions, the total current flowing is the integral of all local current densities over the electrode surface. Having discretised space, the integral is approximated by the sum of (discrete) local currents. For the micro-disk. Fig. 8.3, at each R sample point, the current contribution is equal to gradient G2,(R) or G2(i)/ times the electrode area of the circular strip represented by that point. The total "current" G is thus... 

---