Hydrogen electrocatalytic activity

In addition to these different types of alloys, some studies were also devoted to alternatives to platinum as electrocatalysts. Unfortunately, it is clear that even if some catalytic activities were observed, they are far from those obtained with platinum. Nickel tungsten carbides were investigated, but the electrocatalytic activity recorded for methanol oxidation was very low. Tungsten carbide was also considered as a possible alternative owing to its ability to catalyze the electrooxidation of hydrogen. However, it had no activity for the oxidation of methanol and recently some groups showed that a codeposit of Pt and WO3 led to an enhancement of the activity of platinum. ... 

Petrii OA, Tsirlina GA. 1994. Electrocatalytic activity prediction for hydrogen electrode reaction intuition, art, sceince. Electrochim Acta 39 1739-1747. 

The second most widely used noble metal for preparation of electrodes is gold. Similar to Pt, the gold electrode, contacted with aqueous electrolyte, is covered in a broad range of anodic potentials with an oxide film. On the other hand, the hydrogen adsorption/desorption peaks are absent on the cyclic voltammogram of a gold electrode in aqueous electrolytes, and the electrocatalytic activity for most charge transfer reactions is considerably lower in comparison with that of platinum. 

A.A. Karyakin, E.E. Karyakina, and L. Gorton, The electrocatalytic activity of Prussian blue in hydrogen peroxide reduction studied using a wall-jet electrode with continuous flow. J. Electroanal. Chem. 456, 97-104 (1998). 

The first CNT-modified electrode was reported by Britto et al. in 1996 to study the oxidation of dopamine [16]. The CNT-composite electrode was constructed with bro-moform as the binder. The cyclic voltammetry showed a high degree of reversibility in the redox reaction of dopamine (see Fig. 15.3). Valentini and Rubianes have reported another type of CNT paste electrode by mixing CNTs with mineral oil. This kind of electrode shows excellent electrocatalytic activity toward many materials such as dopamine, ascorbic acid, uric acid, 3,4-dihydroxyphenylacetic acid [39], hydrogen peroxide, and NADH [7], Wang and Musameh have fabricated the CNT/Teflon composite electrodes with attractive electrochemical performance, based on the dispersion of CNTs within a Teflon binder. It has been demonstrated that the electrocatalytic properties of CNTs are not impaired by their association with the Teflon binder [15]. 

In [105], a reduction procedure involving the permeation of hydrogen through palladized Pd sheet electrodes is described. The electrocatalytic activity of various metal (Ti, Zr, Nb, No, Fe, Ni,... 

Platinum electrodes are widely used as an inert electrode in redox reactions because the metal is most stable in aqueous and nonaqueous solutions in the absence of complexing agents, as well as because of its electrocatalytic activity. The inertness of the metal does not mean that no surface layers are formed. The true doublelayer (ideal polarized electrode) behavior is limited to ca. 200-300 mV potential interval depending on the crystal structure and the actual state of the metal surface, while at low and high potentials, hydrogen and oxygen adsorption (oxide formation) respectively, occur. 

Hydrogen evolution is the only reaction for which a complete theory of electrocatalysis has been developed [33]. The reason is that the reaction proceeds through a limited number of steps with possibly only one type of intermediate. The theory predicts that the electrocatalytic activity depends on the heat of adsorption of the intermediate on the electrode surface in a way giving rise to the well known volcano curve. The prediction has been verified experimentally [54] (Fig. 2) and the volcano curve remains the main predictive basis on which the catalytic activity is discussed [41, 55],... 

Studies on single crystal faces have indicated that, on the whole, the crystallographic orientation has a minor influence on the electrocatalytic activity. Of the possible explanations which can be offered [292], a reasonable one is that the high coverage with adsorbed hydrogen far from equilibrium smoothes down the differences in A//ad from face to face. Actually, quantum chemical calculations reproduce more closely the situation at 0H-O, which does not usually correspond to the real situation under cathodic load. Another possibility is that the hydridic... 

The measure of electrocatalytic activity of the powders was the exchange current density (iex), which was found by extrapolation of hydrogen over-current density curves to zero, superpotential. 

Chen X, Li C, Liu Y et al (2008) Electrocatalytic activity of horseradish peroxidase/chitosan/ carbon microsphere microbiocomposites to hydrogen peroxide. Talanta 77 37—41... 

BDD anodes without impurities are not electrocatalytically active because water electrolysis is characterised by the formation of OH radicals (Marselli et al. 2003), ozone (Cho et al. 2005) and hydrogen peroxide (Drogui et al. 2001). One can conclude from radical chemistry that other radicals have to be expected in the anodic reaction layer and, maybe, in the bulk. Foerster and co-workers compared active chlorine formation on Pt and BDD anodes (Foerster et al. 2002). Formation of active chlorine was explained by a mechanism involving the formation of Cl radicals (Ferro et al. 2000) ... 

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