Electrochemical Composition Sensors

Three Major Classes of Electrochemical Solid State Sensors for Redox-Active Gases Relying on Fnll or Partial Eqnilibria . 

Electrochemical sensor Solid phase VAon V/ieon 

The third variant is realized with solid electrolytes (emf 

Let ns consider a signal S which is a function of the concentration (c) of the species j to be detected. Since the sensor will also respond to other species, i.e.. 

Let us discuss the detection of redox active gases, and consider an elemental anion-forming gas E = Cl, , etc.), i.e., 

At sufficiently high temperatures complete equiUbrium (i.e., VPq =Vju = V//q2- = 0) of MO is achieved with the gas phase, and the equiUbrium composition can be usually 

In the ideal case the explicit time dependence — J should 

---

Polarization cell Measurement of kinetic data by polarization Electrochemical composition actors (electrolyzers, pumps, windows), electrochemical composition sensors (amperometric, conductometric)... 

In this section we will describe what may be called electrochemical composition actors, in which chemical action—and not mechanical action as usually described by the term actor (or actuator)—is caused by electrical excitation. Unlike electrochemical composition sensors which detect chemical composition via electrochemical methods, they cause changes in chemical composition. It shall not remain unmentioned that at present interesting work is pursued also to realize mechanical action on an electrochemical stimulus ( artifical muscles ).48... 

Bulk and boundary conductivity sensors have already been discussed in Chapter 5 in relation to equilibrium defect chemistry, potentiometric sensors in the previous section. Nevertheless, we wish — in view of the importance of this application — to sketch out some of the fundamentals of electrochemical (composition) sensors . The fact that a variation in the chemical composition (ck) ehcits a physical signal is the rule rather than the exception. This is merely a necessary sensor criterion. In addition, it is important that a sensor signal exhibits adequate sensitivity , is sufficiently selective, stable and as free from drift as possible , and displays an ad-... 

Conducting (bio)composites applied to electrochemical analysis have opened a new range of possibilities for the construction of electrochemical (bio)sensors for several applications [29-32],... 

There is an extended special literature3,10-16 on applications of solid state electrochemistry and even more on electrochemical devices. According to our objective, in this section applications will be emphasized in which migration and diffusion in the solid state are decisive processes (as discussed in Part I2). We intend to subsume such applications under the headlines composition sensors, composition actors, and energy storage or conversion devices. 

We will begin with a description of electrochemical sensors or more specifically composition sensors based on electrochemical principles (i.e., we refer to an electrochemical detection of composition). Another group of applications refers to devices in which the transference of mass and charge is used primarily to change composition or produce chemicals (electrochemical pumps and electrochemical reactors, or electrochemical filters) we will term such devices composition actors. At the end we will discuss energy conversion and storage devices (which we do not subsume under the term composition actors as here the energy aspect is to the fore). 

Chapter 1 by Joachim Maier continues the solid state electrochemistry discussion that he began in Volume 39 of the Modem Aspects of Electrochemistry. He begins by introducing the reader to the major electrochemical parameters needed for the treatment of electrochemical cells. In section 2 he discusses various sensors electrochemical (composition), bulk conductivity, surface conductivity, galvanic. He also discusses electrochemical energy storage and conversion devices such as fuel cells. 

Shevade, A.V, Homer, M.L., Taylor, C.J., Zhou, H Jewell, A.D., Manatt, K.S., Kisor, A.K., Yen, S.-P.S. and Ryan, M.A. (2006) Correlating polymer-carbon composite sensor response with molecular descriptors. Journal of The Electrochemical Society, 153, H209-H216. 

The first concept is the closed-loop-controlled three-way catalyst. In this, one type of catalyst, which is placed in the exhaust gas stream, is able to promote all the main reactions that lead to the simultaneous removal of carbon monoxide, hydrocarbons and nitrogen oxides. To balance the extent of the oxidation and the reduction reactions, the composition of the engine-out exhaust gas is maintained at or around stoichiometry. This is achieved by a closed-loop engine operation control, in which the oxygen content of the engine-out exhaust gas is measured up-stream of the catalyst with an electrochemical oxygen sensor, also called lambda sensor. 

It is clear that composites in electrochemical gas sensors with liquid electrolytes can be applied only in electrodes and membranes. It was established that the preparation of hybrid composite materials has led to the achievement of modified electrode surfaces that exhibit special properties due to the synergic effect from the individual components. 

Mizutania Y, Matsudaa H, Ishijia T, Furuya N, Takahashi K (2005) Improvement of electrochemical NOj sensor by use of carbon-fluorocaibon gas permeable electrode. Sens Actuators B 108 815-819 Mukundem E, Brosha E, Brown D, Garzon F (1999) Ceria-electrolyte-based mixed potential sensors for the detection of hydroceubons and ceubon monoxide. Electrochem Sohd State Lett 2 412-414 Neikayama S, Sadaoka Y (1994) Preparation of Na3ZrjSijPOjj-sodium aluminosilicate composite and its application as a solid-state electrochemiceil COj gas sensor. J Mater Chem 4(5) 663-668... 

Okamoto A, Suzuki Y, Yoshitake M, Ogawa S, Nakano N (1997) Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering. Nucl Instrum Methods Phys Res B 121 179-183 Polsky R, Gill R, Kaganovsky L, WiUner I (2006) Nucleic acid-functionalized Pt nanoparticles catalytic labels for the amplified elecfrochemical defecfion of biomolecules. Anal Chem 78 2268-2271 Rabinovich L, Lev O (2001) Sol-gel derived composite ceramic carbon electrodes. Electroanalysis 13(4) 265-275 Rabinovich L, Gun J, Tsionsky M, Lev O (1997) Euel-ceU type ceramic-carbon oxygen sensors. J Sol-Gel Sci Technol 8 1077-1081... 

Tsionsky M, Lev O (1995a) Electrochemical composite carbon-ceramic gas sensors introduction and oxygen sensing. Anal Chem 67 2409-2414... 

Among the various types of chemical sensors, defined as devices that transform chemical information ranging from concentration of a specific sample component (analyte) to total compositional analysis into an analytically useful signal [2], electrochemical sensors constitute the largest group in terms of both sensor literature volume and technological applications. They represent approximately 58 % of the total other types include optical (24 %), mass (12 %) and thermal (6 %). As the name implies, electrochemical sensors utilize the effect of the electrochemical interaction between an analyte and an electrode in order to provide continuous information about analyte concentration. Electrochemical gas sensors can be categorized into three main... 

---