Boosting Photocatalytic Nitrogen Fixation via Constructing Low-Oxidation-State Active Sites in the Nanoconfined Spinel Iron Cobalt Oxide

The achievement of both N 2 enrichment and activation of N≡N bonds on active sites in the photocatalytic nitrogen reduction reaction (NRR) under environmental conditions is a long-sought-after goal. Here, a nanoconfined spinel iron cobalt oxide (FeCo 2 O 4 ) is prepared, which has a low oxidation state and stronger Fe’s 3d orbital electron-donating capability of iron active sites and can efficiently transfer electrons to N 2 π* orbitals to facilitate activation of nitrogen. Additionally, we rationally control the mass transfer of nitrogen molecules in a nanoconfined interior cavity via the nanoconfined effect, forcing the N 2 enrichment in the iron cobalt oxide semiconductor. In this work, the NRR performance of the nanoconfined iron cobalt oxide photocatalyst achieves 1.26 μmol h –1 (10 mg of photocatalyst addition), which is 3.7 times higher than that of bulk FeCo 2 O 4 . Our proposed strategy simultaneously satisfies both N 2 capture and activation of nitrogen and instructs the development of low-oxidation-state iron-based photocatalysts for nitrogen fixation.