In the above discussion SHE should be replaced by RHE: reversible hydrogen electrode. This equilibrium potential can be easily measured potentiometrically using Pt/Pt black electrode in the solution saturated with H2.

Hi Yudao,

Pt/C is a very active HER catalyst. As such, if you test the sample within the potential scan range of between 0 V and -0.1 V vs Standard Hydrogen Electrode potential (SHE), you should already get a decent current density. However, you can always extend the lower end potential to more negative values, say -0.3 or -0.5 V vs SHE, if necessary, to have a higher current density (or in order to make comparisons with other less active catalysts). For the higher end potential, it is advisable to extend it to 0.1 or 0.2 V vs SHE.

If you prefer a static potential test, then holding the working electrode (Pt/C) potential at about -0.05V or -0.1 V vs SHE is probably a good starting point.

Your reference electrode is Ag/AgCl. Your reference electrode potential is about 0.2-0.21 V vs SHE, depending on the concentration of KCl in the electrode. So the potential ranges mentioned above should be offset accordingly.

Best,

Kien Cuong

Normal potential (standard potential) is the physical and chemical value  characterising an equilibrium potential difference between an electrode and a solution in that case when the red/ox substances participating in electrode reaction, are in a standard condition, i.e. are equal to their activity (concentration). As the real  potential difference of an electrode and a solution is inaccessible to measurement, use the value characterising potentials of various electrodes concerning so called a reference electrode. Usually the last one is normal Hydrogen electrode which potential is accepted equal to zero at any temperature.

The potential of the HER also depends on the pH, if you're not working under std. conditions.

the electrode used being highly active with respect to the intended reaction; You just have a precise pH of the medium. It is possible to have a significant current from - 0.05 V / SHE

In the above discussion SHE should be replaced by RHE: reversible hydrogen electrode. This equilibrium potential can be easily measured potentiometrically using Pt/Pt black electrode in the solution saturated with H2.