Symmetry-Broken Steered Delocalization State in a Single-Atom Photocatalyst

Single-atom catalysts (SACs) that feature uniform metal active sites with symmetry configurations hold great promise in photocatalysis, while their catalytic efficiency is often restricted by the insufficient inherent activity. Drawing inspiration from hard-soft acid-base theory, here we propose that the delocalized electronic state of single-atom centers can be selectively modulated by adjusting their coordination symmetry, thereby optimizing the adsorption and activation of the reactant molecules. By taking ceria-based Ru-SAC (Ru-CeO₂) as an example, we show that after introducing symmetry breaking, the Ru-CeO₂ with an asymmetric Ru-O₄ configuration (named P-Ru-CeO₂) exhibits highly delocalized electrons with a soft acidic nature, leading to a much higher photocatalytic performance than for pristine Ru-CeO₂ and CeO₂ counterparts. The corresponding inherent mechanism was systematically investigated by spectroscopy and theoretical studies. This work provides an effective strategy for the design and controllable modulation of atomically dispersed catalysts with symmetry-broken configurations, thereby advancing applications in photocatalysis.