Nb 5+ ‐Induced‐CeO 2 Lattice Strain for Robust and Scalable Solar‐Driven Ammonia Synthesis

ABSTRACT Ammonia (NH 3 ) underpins fertilizer production and is emerging as a renewable‐energy carrier. Solar‐driven gas‐phase N 2 /H 2 conversion requires catalysts that couple efficient light utilization with structural stability under H 2 ‐rich conditions. Here, Nb 5+ incorporation into CeO 2 contracts the lattice and induces compressive microstrain, suppressing excessive oxygen‐sublattice reduction and preserving Ru dispersion. In situ NAP‐XPS and computational results show that Nb‐CeO 2 maintains an electron‐enriched Ru working state under reaction conditions, which is further promoted by illumination. Accordingly, 5 wt% Ru/Nb‐CeO 2 achieves an NH 3 synthesis rate of 7.4 mmol g −1 h −1 at 350°C and 0.1 MPa and remains stable for 144 h. Kinetic analyses and in situ DRIFTS indicate that the electronically promoted Ru state alleviates N 2 ‐activation limitations and facilitates subsequent *NH x hydrogenation and NH 3 desorption. Scale‐up synthesis affords a 3 wt% Ru/Nb‐CeO 2 ‐L catalyst stable for 480 h and operable under outdoor concentrated sunlight. A screening‐level analysis estimates a catalyst‐and‐feedstock cost of 286–322 USD t NH3 −1 under the lower‐bound electricity scenario, 42%–51% below the selected Cs‐Ru/MgO benchmark within the same framework. These results identify lattice strain as a promising strategy for simultaneously stabilizing the oxygen sublattice and electronically promoting Ru for efficient solar‐driven ammonia synthesis.