Che Mohamad, Nur Aqlili RianaNur Aqlili RianaChe MohamadChae, KyungheeKyungheeChaeZhou, QiangQiangZhouHuang, Wen‐TseWen‐TseHuangLee, Hyun JeongHyun JeongLeeSon, JaehyunJaehyunSonMoon, JoohoJoohoMoonBu, YunfeiYunfeiBuGong, FengFengGongLiu, Ru‐ShiRu‐ShiLiuKim, JeongwonJeongwonKimKim, Dong HaDong HaKim2025-08-222025-08-222025-06-25https://scholars.lib.ntu.edu.tw/handle/123456789/731569Regulating the orientation and dynamics of interfacial water is essential for optimizing electrocatalytic reactions, yet it remains challenging due to its intrinsic disorder. Here, it is demonstrated that localized surface plasmon resonance (LSPR) on an Ir single-atom Au catalyst actively restructures the hydrogen-bond (HB) network, accelerating ammonia oxidation reaction kinetics. In situ Raman spectroscopy and density functional theory calculations reveal that plasmonic excitation shifts the HB network toward a more flexible configuration, favoring the formation of three-coordinated hydrogen-bonded water (3HB·H2O) while suppressing cation-associated species (K+·H2O). This transformation enhances the dehydrogenation process and stabilizes reaction intermediates, leading to a 28% increase in NH3 oxidation kinetics. Operando X-ray absorption spectroscopy further confirms that LSPR-driven polarization at the Ir active site compresses the Ir─O bond from 1.73 to ≈1.58 Å by generating electron vacancies, thereby accelerating deprotonation with *OH during oxidative electrolysis. Extending this principle to an LED-driven plasmon-assisted symmetric wastewater electrolyzer, achieving a 40-fold current enhancement and 94% ammonia removal efficiency over 120 h at 1 V under landfill leachate-like conditions.enammonia oxidation reactionLED illuminationplasmonicsingle atomsymmetric electrolyzer[SDGs]SDG6[SDGs]SDG7[SDGs]SDG12[SDGs]SDG13journal article10.1002/advs.202507147