Model interpretation of electrochemical behavior of Pt/H<inf>2</inf>SO<inf>4</inf> interface over both the hydrogen oxidation and oxide formation regions

Abstract

© 2019 Hydrogen Energy Publications LLC Hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions are important reactions in the polymer electrolyte membrane fuel cell (PEMFC). However, there are other reactions relating to the kinetics of HOR and ORR, i.e. hydrogen adsorption and oxide formation reactions. Development of the PEMFC catalyst (mostly use Pt) requires kinetic understanding of these reactions taking place at electrodes. In present study, the HOR, ORR, hydrogen adsorption, and oxide formation taking place at Pt/H2SO4 interface were kinetically investigated in the whole potential range. Mechanistic study was performed by establishing kinetic equations from the proposed mechanism, derived to the Faradaic current density and impedance in order to fit to the experimental results. Fitting results indicated that the HOR has more kinetic activity on the Pt(110) than Pt(100) sites with the rate constants of 1.60 and 1.20 s−1, respectively. For the Pt oxidation/reduction process, fitting results showed the fast reaction rate of ORR compared with the Pt oxidation. Additionally from the impedance fitting, the electrical parameters (solution resistance, capacitance, Warburg coefficient, constant phase element parameter) of the electrode reactions were determined to complete the interpretation of the reaction mechanisms. This study demonstrated the acquisition of the mathematical model to predict the kinetic information of an electrochemical reaction. The model can be used to predict the electrochemical behavior of any electrochemical reactions, which is benefit for the design of an electrocatalyst.