Management of Platinum Electronic States through Metal Host-Guest Interactions for Enhanced Oxygen Reduction.

Controlling the electronic states of Pt-based catalysts holds great promise for enhancing the intrinsic activity of the oxygen reduction reaction (ORR). Herein, inspired by first-principles simulations, we propose a strategy using metal host-guest interactions to tune Pt 5d electronic characteristics to optimize the adsorption strength of the key *OH intermediate. The hybrid electrocatalyst of Pt nanoparticles on a single-atom Co-N-C support (Pt@Co SAs) exhibits a half-wave potential of 0.92 V and a mass activity of 3.2 A·mg at 0.9 V in 0.1 M HClO, which is a 20-fold enhancement compared with commercial Pt/C. Impressively, the Pt loading in the catalyst is as low as 1.70 wt %, which represents the lowest value reported in the relevant literature on Pt-based acidic ORR catalysts. Comprehensive spectroscopy investigations and theoretical simulations revealed that the precise regulatory effect of Co in various dispersion states effectively weakens the intermediate adsorption and reduces the energy barrier for the water decomposition step. Our finding provides valuable insights for the development of advanced ultralow-Pt ORR catalysts via the integration engineering of multiple metal sites.