Hydrogen insertion into Pd–Pt–Rh alloy limited volume electrodes (LVEs)☆☆Keynote Lecture. Original Research Article

Limited volume electrodes have been used to examine the processes of hydrogen electrosorption by Pd–Pt–Rh alloys under conditions of cyclic voltammetric (CV) experiments. Hydrogen adsorption and hydrogen absorption signals well separated from surface oxides generation and oxides reduction currents are seen on CV curves recorded in the full potential range. The possibility is demonstrated of simultaneous investigations of bulk processes of hydrogen insertion/removal and surface processes of carbon oxides adsorption. Due to different adsorption characteristics towards CO2 exhibited by the alloy components hydrogen adsorption and hydrogen absorption signals can be distinguished. Adsorbed CO2 causes partial blocking of hydrogen adsorbed on Pt and Rh surface atoms. The presence of adsorbed CO2 on the electrode surface does not influence significantly hydrogen insertion into the alloy. CO adsorption results in a strong inhibition of hydrogen adsorption. Hydrogen insertion into the bulk is not totally blocked but proceeds much slower than in the absence of CO adsorbates.