Balancing Activity and Stability in Phenol Oxidation via In Situ H ₂ O ₂ Generation Over Fe‐Modified AuPd Catalysts

Abstract Harnessing the in situ generation of hydrogen peroxide (H 2 O 2 ) and associated reactive oxygen species (ROS) from molecular hydrogen (H 2 ) and oxygen (O 2 ) offers a powerful and sustainable alternative to conventional oxidative treatments for water purification. In this contribution, we explore the potential of AuPdFe‐based catalysts to achieve the in situ, oxidative degradation of phenol, a widely studied representative organic pollutant. By finely tuning the AuPd/Fe ratio, it is possible to balance H 2 O 2 synthesis with Fe‐mediated ROS generation, achieving efficient phenol degradation and high selectivity toward deeply oxidized products. The optimized catalyst formulation outperforms its bimetallic counterpart by a factor of 10 in conversion efficiency. However, this enhanced activity comes at a cost, with the formation of strongly oxidized species such as formic, oxalic, and malonic acids resulting in the leaching of the active metal components, highlighting a critical trade‐off between catalytic performance and long‐term stability, particularly in the presence of highly concentrated chelating agents.