Theoretical Insights into Enhanced Electrocatalytic Arsenic Oxidation on Au-Decorated Pt Surfaces in Neutral Medium

Abstract

In this study, we present a comprehensive theoretical and experimental investigation of the electrocatalytic oxidation of arsenite on Au immobilized Pt surfaces in a neutral medium. Theoratically, density functional theory (DFT) calculations revealed that thePt-Au bimetallic system exhibits superior adsorption energy (E_ads = -2.045 eV) compared to bare Au (-0.611 eV) and Pt (-0.769 eV) surfaces, indicating enhanced arsenite affinity and catalytic activity. Experimental characterizations, including SEM, PXRD, EIS, and CV, confirmed the formation of noble catalytic sites on Au and synergistic effects between Au and Pt, facilitating efficient As(III) oxidation. The reaction followed first-order kinetics with a diffusion-controlled mechanism, as evidenced by a diffusion coefficient of 3.20 × 10^-7 cm²s^-1. Tafel analysis further elucidated the reaction kinetics, revealing a reduced Tafel slope (277 mVdec^-1) for the Pt-Au electrode, indicative of improved charge transfer. Activation polarization analysis demonstrated lower overpotential (|η_a| = 1.28 V) for thePt-Au system compared to bare Pt (1.56 V), highlighting its enhanced catalytic efficiency and internal synergy after Au deposition. The findings align with theoretical predictions, underscoring the potential of Pt-Au bimetallic surfaces for arsenic sensing.

Keywords: Activation polarization; Arsenic oxidation; DFT; DOS; Gibbs free energy; Tafel slope.