Highly Efficient Nitrate to Ammonia Electrocatalysis Enabled by Inverse Core–Shell Isostructural Cu ₁₄ Nanoclusters

ABSTRACT Electrocatalytic nitrate reduction reaction (NO 3 RR) offers a sustainable route for simultaneous ammonia (NH 3 ) synthesis and nitrate remediation, but it is hindered by insufficient active site regulation and complex reaction pathway competition. Herein, we report a pair of isostructural Cu 14 nanoclusters with inverse core–shell architectures, namely Cu 14 (PPh 3 ) 8 H 12 ( Cu 8 @Cu 6 ‐PPh 3 ) and Cu 14 [P(PhOCH 3 ) 3 ] 8 H 12 ( Cu 6 @Cu 8 ‐P(PhOCH 3 ) 3 ), as model catalysts to decode the structure‐electronic activity relationship in NO 3 RR. Structural inversion triggers two key modulations: reorganization of surface hydride coordination environments (µ 3 ‐CuH 3 /µ 2 ‐CuH 2 for Cu 8 @Cu 6 ‐PPh 3 vs. µ 3 ‐CuH 3 /µ 2 ‐CuH 3 for Cu 6 @Cu 8 ‐P(PhOCH 3 ) 3 ) and precise tuning of Cu active site electron density. Benefiting from these synergistic effects, Cu 8 @Cu 6 ‐PPh 3 exhibits exceptional NO 3 RR performance with a maximum Faradaic efficiency (FE NH3 ) of 97.1% and an NH 3 yield rate of 37.4 mg mg cat −1 h −1 , outperforming Cu 6 @Cu 8 ‑P(PhOCH 3 ) 3 (66.1%, 20.1 mg mg cat −1 h −1 ). Combined in situ characterizations (FTIR, DEMS) and DFT calculations reveal that core–shell inversion lowers the energy barrier of the rate‐determining step and reduces NH 3 desorption energy (0.14 vs. 0.87 eV), thereby promoting sequential nitrate reduction via NO 3 − →NO 2 − →NO→ * NH x →NH 3 . This work establishes a “core–shell inversion engineering” strategy for designing high‐performance electrocatalysts through atomic‐level electronic‐structural coupling, opening new avenues for sustainable NH 3 synthesis and environmental remediation.