Surface Dynamic Redox Modulation of CuFe Achieving Near‐Unity Selectivity in Solar‐Integrated Nitrate‐to‐Ammonia Conversion

ABSTRACT Electrocatalytic nitrate reduction (NO 3 − RR) provides a sustainable pathway for NH 3 production under ambient conditions. Although operation in neutral media is more practically relevant, the reaction generally suffers from sluggish kinetics and unfavorable hydrogenation steps, which collectively limit NH 3 selectivity. Here, we develop a graphene‐encapsulated CuFe alloy catalyst (CuFe‐G) that enables highly efficient NO 3 − RR via a dynamically generated CuFe δ+ surface active layer. The synergistic alloy interface drives the spontaneous conversion of NO 3 − to NO 2 − , while in Situ surface redox dynamics create an active CuFe δ+ layer that optimizes *NO adsorption and accelerates hydrogenation kinetics. In parallel, encapsulation of the dynamic CuFe δ+ species within multilayer graphene constructs a mechanically robust and highly conductive interface that stabilizes the active sites and facilitates rapid charge transport. As a result, CuFe‐G delivers a peak NH 3 Faradaic efficiency of 99.63% at −1.0 V vs. RHE, together with an NH 3 yield rate of 8.03 mg h −1 mg cat −1 . When integrated into a CuFe‐G‖RuO 2 electrolyzer, the system further achieves a current density of 400 mA cm −2 at 2.6 V and maintains a solar‐to‐ammonia efficiency of 4.1% under fluctuating illumination. This work therefore establishes a dynamically redox‐regulated catalytic platform for sustainable, solar‐driven nitrate‐to‐ammonia conversion.