Platinum hydrogen evolution reaction

Both schemes have been observed in various systems. We consider hydrogen evolution on platinum from an aqueous solution in greater detail. In this system the Volmer-Tafel mechanism operates, the Volmer reaction is fast, the Tafel reaction is slow and determines the rate. Let us denote the rate constant for the Volmer reaction as ki(rj), that of the back reaction as k i(rj). Since the Volmer reaction is fast and in quasiequilibrium, we have ... 

We have shown that the hydrogen evolution reaction on platinum is... 

The consequence of all these effects is that oxygen, or hydrogen, evolution reactions follow quite different kinetics than would be expected from thermodynamical considerations. For example, oxygen evolution on a platinum electrode starts at a potential significantly higher than that predicted by the Nernst equation. The reason for this is the formation of surface oxide and its associated dynamics as elucidated, besides others, by B. Conway [4]. 

The Pt-H atom interaction plays a key role in electrochemistry, particularly at the Pt/aqueous solution interface in the range of the potentials related to the H-adatom electrosorption equilibrium and hydrogen evolution reaction. The situation outlined above suggested the convenience of attempting a quantum chemistry approach to surface species that are likely formed at a simulated platinum/aqueous electrochemical interface in order to discriminate the structure and energy of possible H-adsorbates. This is a relevant issue in dealing with, for instance, the interpretation of the complex electrosorption spectra of H-atoms on platinum in an aqueous solution, as well as to provide a more realistic approach to the nature of H-atom intermediates involved in the hydrogen evolution reaction. 

An electrochemical study of platinum and nickel deposition on silicon from fluoride solutions at the open circuit potential is presented. In the steady-state situation, the silicon oxidation current is balanced with a cathodic current such as to yield net zero current. In the case of platinum, the prevailing cathodic process is platinum deposition by hole injection into the valence band. In nickel solutions, a competition is established between nickel reduction and hydrogen evolution at pH=8 metal deposition is the prevailing reaction, either through a valence band process on p-type silicon or through a conduction band process on n-type. On the contrary, at pH<1 the hydrogen evolution reaction is kinetically faster and nickel deposition is not observed. The anodic and cathodic processes are coupled through the formation of silicon surface states. 

It has been demonstrated that NjO can be reduced on silver [48]. A recent study by Parsons and coworkers has shown that the gas can also be reduced on platinum [49]. Using single crystal electrodes they showed that the reduction is closely associated with the hydrogen evolution reaction. This my also be a source of error in oxygen measurement if too high a reduction potential is applied to the working electrode. 

For the hydrogen evolution reaction on platinum, for example, k 10 A/cm, but on mercury, io A/cm. It is, in fact, these values of io that allow us to use platinum as the electron collector for a reversible hydrogen electrode and prevent our using mercury for this purpose. 

The most likely explanation is the effect of radiation on the electrolytic solution. The study of the effect of radiation on the hydrogen evolution reaction on platinum in sulfuric acid supports this view. 

Other than for alkaline electrolysis, platinum (cathode) and iridium (anode) are used as catalysts. To reduce costs, carbon supported platinum is used to catalyze the hydrogen evolution reaction. Unfortunately, this is not possible on the anode side. The evolving oxygen at a potential of 1.7 V to 2 V would corrode the carbon material in a short time. 

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