Hydrogen cathodes

Amorphous materials are usually highly corrosion resistant this quality has first attracted the attention of electrochemists [567, 568]. Recent reviews are available in the literature [569, 570]. The idea of applying amorphous materials to hydrogen cathodes is very recent [571] most of the papers on this subject have appeared during the past few years. The hope for good electrocatalytic properties is based on the good performances observed in specific catalytic processes. 

This chapter has been devised to provide a broad survey of the state of the art of research and applications in the field of hydrogen cathodes. Analysis of problems was preferred to mere recipes of preparation and sterile quotations of experimental parameters. Although the main target has been to illustrate the special demands for application, the chapter provides in fact an interplay between theory and practice, emphasizing on one hand the importance of theory in guiding research and development, and on the other hand the irreplaceable role of the feedback from experiments to orient theory. 

E8.1. Values of the hydrogen cathodic current density, and steady state hydrogen permeation current, joo. a function of the overpotential, ij, measured using the Devanathan-Stachurski technique are given in Table E8.1. 

Yu-Min Tsou, Novel High performance Hydrogen Cathode Coating, In Proc. Vol 99-21, The Electrochemical Society Inc., Princeton, NJ (1999), p. 160. 

LBL film containing [NaPsWsoOno] , a feature that designates this assembly as a potential hydrogen cathode [194] finally, several examples were described that concern the electrocatalytic reduction in... 

In cases where more than one product may be formed, particuarly when the relative yield is potential dependent, potentiostatic electrolysis is particularly desirable. If a controlled constant current electrolysis is carried out in such a case, the potential will generally increase with time as the reactant is consumed, so that eventually the diffusion-limited current is reached, which itself eventually becomes smaller and smaller and the remaining fraction of the current is then passed by decomposition of the solvent or supporting electrolyte, usually with evolution of hydrogen (cathodic processes) or oxygen (anodically) in the case of an aqueous medium. 

Tilak BV, Tari K, Hoover CL (1988) Metal anodes and hydrogen cathodes - their activity towards O2 evolution and CIO3" reduction reactions. J Electrochem Soc 135 1386-1392. doi 10.1149/ 1.2095999... 

In contrast, for acidic water with a pH<4.5 approximately, the risk of corrosion is much higher. The hydrogen cathode acts as illustrated by the following reaction ... 

F(x a reversible electrode, Evans diagram allows the determination of the corrosion point where both the hydrogen cathodic and the metal anodic line intercept. On the other hand, the irreversible electrochemical behavior denoted by the cathodic and anodic Stem diagram is also used for determining the corrosion point by simply extrapolating the linear portions of both curves until the... 

It is perhaps worth restating that the above analysis rests on the assumptions that the BCC B2 phase is a good hydrogen cathode and that AlgMn5 is not. 

There is still a lack of experiments on the hydrogen cathodic reactions with well-controlled surface coverages by hydrogen, oxygen, and adsorption blockers, characterizing particularly the influence of the blockers on the occupancy of the subsurface sites. Such studies are needed to fully understand the surface processes involved in H-induced cracking of metals and alloys. 

SCC is defined as the growth of cracks due to the simultaneous action of a stress (nominally static and tensile) and a reactive environment. For metals, "reactive" excludes gaseous hydrogen, cathodic polarization, and liquid metals but includes aqueous and nonaque-ous electrolytes and reactive atmospheres (H2O, I2, CI2). Related phenomena occur in inorganic glasses and ceramics, especially in water, and are thought to be involved in major... 

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