Architecture Engineering and Phase Engineering of Rhodium Metallene Co‐Boost Nitrite‐to‐Ammonia Electroconversion

Abstract Electrocatalytic nitrite reduction reaction (NO 2 RR) offers an effective strategy for sustainable ammonia (NH 3 ) synthesis and N‐pollutants wastewater degradation. Herein, we propose a dual‐engineering strategy by combining architecture engineering and phase engineering on nanosheet‐like rhodium metallene (Rh‐NS) coupled with twisted nanoribbon‐like rhodium metallene (Rh‐NR) nanoarchitectonics (Rh‐NS/Rh‐NR) to boost NO 2 − ‐to‐NH 3 electroconversion. Rh‐NS/Rh‐NR, characterized by a high density of unsaturated coordination sites and a large specific surface area, greatly enhances the adsorption capacity of NO 2 − and crucial intermediates and lowers the energy barrier for the rate‐determining step of *NOH formation from *NO. Consequently, Rh‐NS/Rh‐NR exhibits satisfactory Faradaic efficiency (FE) of 98.7% and a remarkable NH 3 yield rate of 44.3 mg mg cat −1 h −1 for NO 2 RR at high reduction potential (0.00 V). Using Rh‐NS/Rh‐NR as cathode, the assembled zinc–nitrite battery delivers excellent discharge performance (24.2 mW cm −2 ) and promising NH 3 synthesis capacity (5.96 mg mg cat −1 h −1 ). This work not only guides the architecture‐engineering design of metallene but also demonstrates the practical potential of zinc–nitrite batteries in integrated energy‐environmental applications.