Nb 5+ ‐Induced‐CeO 2 Lattice Strain for Robust and Scalable Solar‐Driven Ammonia Synthesis
Can Li, Jin‐Tao Ru, Jiaxuan Li, Tengshijie Gao, Yi‐Ming Liu, Rui‐Min Zhang, Hai‐Xia Liu, Xiao‐Fang Wang, Xiaotong Chen, Kaiyi Su, Zhi‐Jun Li, Chen Ye, Chen‐Ho Tung, Li‐Zhu WuABSTRACT
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.