Enhancement of Nitrate‐to‐Ammonia on Amorphous CeOx‐Modified Cu via Tuning of Active Hydrogen Supply

The electrochemical nitrate reduction reaction (NO3RR) is an environment‐friendly and promising alternative to the conventional Haber–Bosch ammonia synthesis process, which is a complex process of proton‐coupled electron transfer. Hereon, the amorphous CeOx support introduced to construct Cu/a‐CeOx heterostructure is prepared to provide sufficient *H and synergistically catalyze the NO3RR. Cu/a‐CeOx achieves a maximum ammonia yield of 1.52 mmol h−1 mgcat−1. In the flow cell, the NH3 yield reaches 17.93 mmol h−1 mgcat−1 at 1 A cm−2, which exceeds most of the state‐of‐the‐art catalysts. In situ X‐ray diffraction (XRD) and in situ Raman observe that the catalyst undergoes structural reconfiguration under operating conditions, thus confirming that Cu2O is not the true active center in the catalytic process. Furthermore, in situ characterizations and density functional theory (DFT) calculations demonstrate that the amorphous CeOx in Cu/a‐CeOx modulates the electronic structure of Cu and overcomes the higher potential barrier required for the decomposition of water on Cu, which greatly facilitates the hydrolysis process and provides a higher H‐coverage rate for the hydrogenation of NO3−, realizing a dynamic equilibrium between the production and consumption of active hydrogen. This component design strategy centered on the amorphous structure opens up a new pathway for the electrochemical NO3RR. Cu on amorphous CeOx facilitates H2O splitting to generate abundant *H, which is combined with *NO intermediate produced by deoxygenation and hydrogenation of adsorbed NO3− to form ammonia via hydrogen spillover mechanism.