Lattice-Confined Single-Atom Fe₁ S_x on Mesoporous TiO₂ for Boosting Ambient Electrocatalytic N₂ Reduction Reaction

Mimicking natural nitrogenase to create highly efficient single-atom catalysts (SACs) for ambient N₂ fixation is highly desired, but still challenging. Herein, S-coordinated Fe SACs on mesoporous TiO₂ have been constructed by a lattice-confined strategy. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy spectra demonstrate that Fe atoms are anchored in TiO₂ lattice via the FeS₂ O₂ coordination configuration. Theoretical calculations reveal that FeS₂ O₂ sites are the active centers for electrocatalytic nitrogen reduction reaction (NRR). Moreover, the finite element analysis shows that confinement of opened and ordered mesopores can facilitate the mass transport and offer an enlarged active surface area for NRR. As a result, this catalyst delivers a favorable NH₃ yield rate of 18.3 μg h^-1  mg_cat. ^-1 with a high Faradaic efficiency of 17.3 % at -0.20 V versus a reversible hydrogen electrode. Most importantly, this lattice-confined strategy is universal and can also be applied to Ni₁ S_x @TiO₂ , Co₁ S_x @TiO₂ , Mo₁ S_x @TiO₂ , and Cu₁ S_x @TiO₂ SACs. Our study provides new hints for the design and biomimetic synthesis of highly efficient NRR electrocatalysts.