Visible-Light-Driven Ammonia Photosynthesis on Mo₇-Cluster Stabilized CeO₂ Nanocore Through Interfacial Charge...

A [Mo₇O₂₄]^6--cluster is used herein to stabilize a vacancy-rich CeO₂ nanocore (Mo₇@CeO₂) with high aqueous dispersity and wide-pH stability, possessing a band structure to harvest the visible-light for photoreduction of [NO₃]^- to ammonia. Covalent-type atomic connectivity of the Mo₇-clusters to CeO₂ nanocore is established by advanced spectroscopies. In situ electron paramagnetic resonance (EPR) with photogenerated hole and electron capturing reagents, femtosecond transient absorption spectroscopy (fs-TAS), and in situ Kelvin probe atomic force microscopy (KPFM) studies probe the interfacial charge transfer in this type-II heterostructure, which favors the efficient exciton separation and enhances the lifetime for the photosynthesis of NH₃ (>95%) with an exceptionally high yield rate ≈332 mg h^-1. A computational study emphasizes an internal electric field (IEF) formation and hole retention on the CeO₂ and electron localization in the Mo₇ cluster. ¹⁵N-labeling study confirms the source of nitrogen in photogenerated NH_3, while pH-variation and D-labelling studies infer that the photochemical deoxygenation of nitrate is coupled with hydrogenation. This study highlights the pivotal role of an inorganic ligand in regulating the size of the metal-oxide core, modulating the band alignment, and charge transfer dynamics for photoconversion, which is further demonstrated as a potential strategy for ammonia photosynthesis using wastewater and sunlight.