Ruthenium dioxide (RuO₂) is a promising and cost-effective substitute for iridium oxide in the acidic oxygen evolution reaction (OER), but its application is hindered by the intrinsic trade-off between catalytic activity and stability due to the dissolution of high-valent metal sites. Herein, we design a heavy p‑block element Bi-modified RuO₂ electrocatalyst in which the lone‑pair electrons of Bi stabilize low‑valence Ru and introduce tensile strain, yielding weakened metal–oxygen covalency and overcoming the activity–stability limitation. In situ spectroscopies confirm that the Bi lone‑pair inhibits Ru overoxidation, ensuring outstanding structural stability of Bi_0.2Ru_0.8O₂, and simultaneously promote the formation of the pivotal *OOH intermediate, confirming a stable adsorbate evolution pathway instead of the traditional lattice oxygen mechanism. This highlights the critical role of bond covalency in stabilizing surface Ru and oxygen sites for enhanced acidic‑OER durability. As a result, the Bi_0.2Ru_0.8O₂ electrocatalyst delivers an ultralow overpotential of 269 mV at 100 mA cm^-2 and a small Tafel slope of 65.8 mV dec^-1. When implemented as the anode catalyst in a practical proton-exchange membrane water electrolyzer, Bi_0.2Ru_0.8O₂ enables a current density of 3.0 A cm^-2 at a cell voltage of only 1.837 V and sustains stable operation for 40 h at 200 mA cm^-2.

Rational modulation of Fe-N₄ coordination symmetry through heteroatom doping with distinct electronegativities has emerged as a promising strategy to optimize the performance of the oxygen reduction reaction (ORR). Here, we systematically investigate the less electronegative sulfur- and phosphorus-doped Fe single-atom catalysts and demonstrate that the S-doped catalyst (Fe-SNC) achieves superior ORR activity (E_1/2 = 0.904 V vs. RHE), surpassing both the P-doped Fe-PNC and the undoped Fe-NC control samples, while maintaining exceptional durability. Synchrotron radiation X-ray absorption spectroscopy verified the precise engineering of the asymmetric Fe-S₁N₃ and Fe-P₁N₃ configurations within the ZIF-8-derived carbon matrices, confirming successful manipulation of the first coordination sphere. In situ synchrotron radiation infrared spectroscopy further elucidates accelerated *OOH dissociation kinetics in Fe-SNC, which benefits from the optimization of the electronic structure of Fe 3d by S doping. These findings conclusively establish geometric symmetry breaking via electronegativity-driven electronic modulation as an effective strategy for advancing metal-N₄ catalyst design.