Breaking the Intermediate Solvation Shell on Single‐Atom Catalysts With a Proximal Group Perturber for Enhanced Oxygen Reduction

ABSTRACT The electrocatalytic performance is governed by the immediate microenvironment surrounding the active site, particularly the hydrogen‐bond network that stabilizes reaction intermediates. While cation effects in aqueous electrolytes allow tuning of this network, this powerful leveraging is absent in proton‐exchange membrane fuel cells (PEMFCs), where proton is the sole cation. Here, we demonstrate a general strategy of “immobilized molecular perturbation” for single‐atom catalysts, which moves the tuning function from the electrolyte to the catalyst's second coordination sphere. Using the oxygen reduction reaction (ORR) on Fe─N─C as a model, we demonstrate that proximal P─O groups act as steric and hydrogen‐bonding perturbers. This engineered microenvironment selectively weakens the solvation shell of key * OH intermediates, as confirmed by spectroscopy and computations, thereby facilitating the rate‐determining step of * OH desorption. This regulation endows the catalyst with exceptional performance, achieving a half‐wave potential of 0.861 V in 0.5 m H 2 SO 4 and a peak power density of 1024 mW cm −2 in a H 2 /O 2 PEMFC. Furthermore, it exhibits outstanding stability with 72 % current retention after 253 h at 0.65 V, positioning it among the best‐reported non‐precious metal catalysts. This work shifts the paradigm from exclusive active‐center optimization to deliberate local microenvironment engineering, enabling accelerated electrocatalysis in device‐relevant environments.