The Hydrogen-Evolution Reaction on Platinum

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

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. 

The rate of the hydrogen evolution reaction on Sn when coupled with 1 cm platinum decreases from /hj.Sh to /H2,Sn-Pt(i cm ). 

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. 

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. 

Hydrogen evolution rate on the tin surface increases when tin is coupled with inert platinum. The observed increase in Fig. 6.6 results from the exchange current density difference of the coupled metals. The intersection between the tin dissolution polarization curve and the polarization curve for hydrogen evolution on tin results in fcorr.Sn- When equal surface area of tin (1 cm and platinum (1 cm are coupled, the sum of the rates of hydrogen evolution reactions on both metals is equal to the total rate of hydrogen evolution. 

The corrosion rate and corrosion potential are estimated using electrochemical kinetic parameters such as exchange current density for hydrogen evolution reaction on titanium and platinum, reversible potentials, and cathodic and anodic slopes. 

Tafel slope for tin dissolution is fca = 0.1 V/decade. The Tafel slopes for hydrogen evolution reaction on both tin and platinum is bc = — 0A/decade. Exchange current density for hydrogen evolution on Sn, sn 10 A/cm and on Pt,... 

Platinum is an inert metal and the rate of hydrogen evolution is orders of magnitude greater than that on metallic zinc (exchange cmrent density for the hydrogen evolution reaction in IN HCl is 10 Acm on Pt and 10 Acm on Zn in H2SO4). 

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