Operando X‐ray Absorption Study of TiO₂‐Supported Au, Cu, and Au–Cu Catalysts for Butadiene Selective Hydrogenation

Abstract The selective hydrogenation of unsaturated hydrocarbons is essential for the production of alkenes used in polymerization processes. Au‐based catalysts offer greater selectivity than Pd but are limited by poor hydrogen activation. Alloying Au with Cu offers a promising approach to enhance catalytic performance by improving activity while retaining excellent selectivity. The structural dynamics of TiO₂‐supported monometallic (Au, Cu) and bimetallic (AuCu, AuCu 3 ) catalysts were investigated during the reduction step where metal nanoparticles are structured, and the selective hydrogenation of butadiene, using operando X‐ray absorption spectroscopy (XAS) and ex situ scanning transmission electron microscopy (STEM). XANES investigation shows that the temperature at which both metal precursors are reduced during the reduction step is strongly influenced by the alloy composition. This is explained by a Au 0 assisted reduction of Cu 2+ species mediated by H 2 spillover. EXAFS shows that Au maintains its metallic state during the catalytic reaction, while Cu shows minor electronic changes without forming segregated CuO phases. EXAFS also indicate a synergistic effect in AuCu/TiO 2 catalyst. STEM‐HAADF investigation reveals that the crystalline structure of AuCu nanoparticles after reaction is more robust against size‐dependent structural changes compared to pure Au, suggesting that alloying Cu with Au plays a role in the nanoparticle's stability.