Mechanism of hydrogen evolution

Bockris, J. O M. and Potter, E. C. (1952) The mechanism of hydrogen evolution at nickel cathodes in aqueous solutions. 

One of the questions in the mechanism of hydrogen evolution, and ancillary topics connected with the surface hydrogen involved in corrosion, is the dependence of the surface hydrogen upon overpotential. This topic has importance not only because of the... 

Baba R, Nakabayashi S, Fujishima A, Honda K (1985) Investigation of the mechanism of hydrogen evolution during photocatalytic water decomposition on metal-loaded semiconductor powders J Phys Chem 89 1902-1905... 

The intermediate remains on the electrode until it is transformed into another particle during the consecutive steps that make up the overall reaction. The simplest example is (Section 7.6.2) the mechanism of hydrogen evolution, in which one possible step involves chemical recombination between adsorbed H s, put onto the electrode surface by means of the discharge of H20+ from acid or H20 from alkaline solutions. The adsorbed H is the intermediate radical. 

In previous material—when discussing the mechanisms of hydrogen evolution— the value 0H has been an important factor in the argument. For example, if Gjj is laige (approaching unity), it is likely that the mechanism of desorption of H from the surface to form H2 will be via the electrochemical desorption step rather than that of recombination. 

The mechanism of hydrogen evolution is classically based [33, 184, 185] on a primary discharge step ... 

The mechanism of hydrogen evolution has been briefly investigated both in acid... 

The mechanism of hydrogen evolution has been investigated by impedance measurements [371] and hydrogen-tritium kinetic isotope effects [375]. The effect of halides dissolved in solution has been studied [372, 376] these ions increase the overpotential in the sequence Cl- Adsorption isotherms for halides have been derived. They conform to the Temkin adsorption model with partial charge transfer. The lateral interaction between adsorbed particles has been calculated. It is higher for Br- than for I- and increases with overpotential on account of the weakening in the metal-halide bond. Thus, halides are substantial poisons for hydrogen evolution on iron. Poisons also include metal ions such as Cd2+, Zn2+, and Mn2+ [26]. 

The mechanism may change from acids to alkalis in some cases [365], This may be related to the higher sensivity of the Fe surface to oxidation in alkaline solutions [365, 367], Actually, the corrosion of Fe proceeds also under moderate cathodic load [368]. Impedance measurements have suggested that the classical mechanisms of hydrogen evolution is probably inadequate to describe the situation on Fe [377], A surface diffusion step with spillover of hydrogen to sites with lower M-H energy has been suggested. Adsorption of CN- interferes with such a diffusion. 

Several studies have addressed the mechanism of hydrogen evolution on passive metals or bulk semiconducting oxides. Even on Ti the activity improves with the oxygen content as Ti-O alloys are formed. A maximum is observed around 30% oxygen [464], The Tafel slope is somewhat larger than 120 mV. However, on cathodical-ly treated TiOz hydrogen can be evolved with 60 mV slope in the presence of residual Ti02. An increase in oxide thickness depresses the catalytic activity [465]. 

F. P. Healey, 1970. The mechanism of hydrogen evolution by Chlamydomonas moewusii. Plant. Physiol AS, 153-159... 

In the presence of redox couples, the relative contribution and mechanism of hydrogen evolution may change, the detail of which can be found in Ref. 3. 

M.A.V. Devanathan, L. Stachurski, Mechanism of hydrogen evolution on iron in acid solutions by permeation rates, J. Electrochem. Soc. Ill (1964) 619-623. 

The mechanism of hydrogen evolution from hydridocobaloxime [HCo-(dmgH)a(P8u"3)] involves two pathways representing reactions of different protonated forms of the complex ... 

H. Houda, Y. Naoki, and H. Obanawa, Characteristics of Plasma-Sprayed NiO Cathode and Mechanism of Hydrogen Evolution Reaction at its surface. In Proc. Vol 98-10, The Electrochemical Society Inc. (1998), p. 329. 

The nature of the adsorbed intermediate (Hajs) and its impact on the mechanism of hydrogen evolution has been a major concern in HER electrocatalysis. Platinum has long been known to form adsorbed hydrogen [4], and the adsorption of hydrogen holds a particular significance in the overall development of modern electrochemical surface science. 

The general mechanism of hydrogen evolution reaction is based [12, 13] on the following three steps ... 

Vaccaro L, Artero V, Canaguier S, Fontecave M, Field MJ. Mechanism of hydrogen evolution catalyzed hy NiFe hydrogenases insights from a Ni-Ru model compound. Dalton Trans 2010 39 3043-3049. 

In neutral and alkaline solutions, the mechanism of hydrogen evolution is completely different from that in acidic solutions. H+ ions are not available. Therefore, hydrogen has to be produced by water decomposition. This reaction has larger activation energy and... 

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