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

The achievement of both N2 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 (FeCo2O4) 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 N2 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 N2 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 FeCo2O4. Our proposed strategy simultaneously satisfies both N2 capture and activation of nitrogen and instructs the development of low-oxidation-state iron-based photocatalysts for nitrogen fixation.