Copper Single Atoms on a Photothermal Heterostructure for Dual‐Field‐Driven Nitrate‐to‐Ammonia Conversion

ABSTRACT Electrocatalytic reactions involving multiple electrons and protons, such as nitrate reduction to ammonia, are constrained by sluggish interfacial charge‐transfer and inefficient mass transport. Here, we propose a dual‐field‐driven strategy that integrates the local thermal field and the built‐in electric field within a photothermal heterostructure, enabling concerted control over both atomic‐scale active‐site construction and the reaction microenvironment. Using a CeO 2 /Co 3 O 4 composite as the platform, photogenerated electrons guided by interfacial band alignment drive the site‐selective loading of single‐atom Cu onto CeO 2 domains, yielding an atomically precise Cu/CeO 2 /Co 3 O 4 (Cu/CeCo) catalyst. Under near‐infrared irradiation, the optimal catalyst provides an NH 3 yield rate of 110.5 µmol h −1 cm −2 at −0.4 V vs. RHE and a high Faradaic efficiency of 95.8% at −0.2 V vs. RHE, both outperforming its dark‐state performance. Mechanistic studies indicate that Cu single atoms anchored on CeO 2 /Co 3 O 4 promote NO 3 − adsorption and effectively inhibit the hydrogen evolution reaction. Furthermore, the dual‐field accelerates the interfacial charge transfer and promotes the overall reaction kinetics. This work demonstrates that dual‐field microenvironment engineering serves as a promising platform for advancing atomic‐scale catalysis toward sustainable chemical synthesis.