Oxygen reduction reaction features in neutral media on glassy carbon electrode functionalized by chemically prepared gold nanoparticles

Gold nanoparticles (AuNPs) were prepared by chemical route using 4 different protocols by varying reducer, stabilizing agent and solvent mixture. The obtained AuNPs were characterized by transmission electronic microscopy (TEM), UV-Visible and zeta potential measurements. From these latter surface charge densities were calculated to evidence the effect of the solvent mixture on AuNPs stability. The AuNPs were then deposited onto glassy carbon (GC) electrodes by drop-casting and the resulting deposits were characterized by cyclic voltammetry (CV) in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The electrochemical kinetic parameters of the 4 different modified electrodes towards oxygen reduction reaction (ORR) in neutral NaCl-NaHCO3 media (0.15 M / 0.028 M, pH 7.4) were evaluated by rotating disk electrode voltammetry and subsequent Koutecky-Levich treatment. Contrary to what we previously obtained with electrodeposited AuNPs [Gotti et al., Electrochim. Acta 2014], the highest cathodic transfer coefficients were not obtained on the smallest particles, highlighting the influence of the stabilizing ligand together with the deposits morphology on the ORR kinetics

Hydrogen Evolution Reaction on Palladium Multilayers Deposited on Au(111): A Theoretical Approach

We have investigated the electrocatalytic properties of multilayers of Pd epitaxially deposited on Au(111). In contrast to the numerous previous works in this area, we have focused on the kinetics of the electrochemical step for hydrogen adsorption (Volmer reaction) and determined its energies of activation. We have used a combination of density functional theory calculations and our own theory of electrocatalysis, which allows us to investigate the systems in an electrochemical environment. Contrary to our previous work with a submonolayer of Pd in Au(111), the activation barrier for the hydrogen adsorption process from proton is very low or almost zero for all bimetallic systems investigated. It is about 0.2 eV for pure Pd(111). In the case of two layers of Pd on Au(111) containing absorbed hydrogen in the subsurface, the adsorption free energy is less negative and the barrier lower than for the other investigated systems. This is in agreement with experimental data that shows a larger activity for hydrogen oxidation with hydride Pd systems