Enhancing photocatalytic activity through the manipulation of intrinsic electric fields in yolk–shell hollow AuPd@TiO2 structures

Abstract

Photocatalysis driven by light exhibits significant potential for degrading volatile organic compounds (VOCs), yet developing cost-effective photocatalytic technology remains a substantial challenge. Herein, we demonstrate an innovative strategy to fabricate a yolk–shell bimetallic AuPd combined with hollow TiO₂ photocatalyst (AuPd@TiO₂) with controllable atomic ratios of Au to Pd. Au₃Pd₁@TiO₂ achieved 100% degradation of toluene and 75% degradation of ortho-dichlorobenzene (o-DCB) within 3 hours under LED light illumination, corresponding to TOC removal rates of 93% and 73%, respectively. Characterization and Density Functional Theory (DFT) calculation confirmed that the direction of the built-in electric field reversed with decreasing Au to Pd ratios, and the absolute value of the potential first decreased and then increased, favoring low-energy, high-efficiency catalytic reactions. Furthermore, varying the atomic ratios of Au to Pd altered the electronic interactions between atoms, resulting in a shift in the d-band center closer to the Fermi level. The diminished occupancy of the antibonding orbital in Au₃Pd₁@TiO₂ results in the stabilization of the AuPd 3p–d antibonding, and promotes the bonding strength of atomic AuPd on O sites, which would facilitate the electron transportation efficiency between AuPd nanoparticles (NPs) and TiO₂. Therefore, this shift optimized the adsorption energy levels for Au₃Pd₁@TiO₂, facilitating rapid catalytic reactions and efficient product desorption, thereby enhancing the catalytic degradation rate. This study presents an efficient and innovative photocatalyst and makes significant progress in elucidating how different AuPd NP ratios on TiO₂ enhance photocatalytic activity.