Site Blocking with Gold Adatoms as an Approach to Study Structural Effects in Electrocatalysis

Theoretical approach to energy levels applied to modified surfaces

The main objective of this work is to present a new theoretical basis to describe surface deposition on a modified electrode surface. The surface is modified via the irreversible deposition of fixed particles or impurities that can block a fraction of the adsorption sites. An electroactive species was allowed to adsorb to the accessible sites and transfer electric charge. Energetics interactions between the electroactive particles and impurities were considered. The theoretical approach of energy levels (TAEL) was presented, through the integral equation formalism, where for its formulation the binomial distribution of energy levels and the standard Langmuir isotherm were considered. Adsorption isotherms and the compressibility of the adsorption layer were compared with Monte Carlo simulations and the recently published modified mean field approach (MMFA). Various conditions were studied: attractive and repulsive lateral interactions, and different quantities of impurities in one- and two-dimensional lattices. The performance of the theoretical approximations was analyzed by calculating an integral error.

Mean field approach applied to surface deposition on a modified electrode

In this work we study the deposition phenomena on a modified electrode in the framework of the mean field theory. The electrode surface is modified by irreversible deposition of impurities which can block a fraction of the adsorption sites. Then, an electroactive species is allowed to adsorb on the accessible sites, transferring electric charge and generating a current that can be calculated and measured. Nearest-neighbor lateral interactions are considered both between electroactive particles and between particles and impurities. A modified Bragg-Williams theoretical approach considers both the blocking effects of impurities and the lateral interactions, through different concentrations of impurities and particles. The analysis is based on the study of adsorption isotherms and voltammograms, considering different interaction energies and impurity concentrations. The potentialities and limitations of the analytical approximation are discussed by comparing theoretical predictions with Monte Carlo simulations and experimental measurements in which artificial clay represents the impurity and a [Fe(CN)₆]⁴ redox probe is the species that transfers the charge.

Oxygen reduction reaction activity and structural stability of Pt–Au nanoparticles prepared by arc-plasma deposition

Sequential arc-plasma deposited Pt–Au alloy nanoparticles show superior electrochemical structural durability compared with arc-plasma deposited Pt nanoparticles before and after electrochemical potential cycles.