Nitrogen-Activation and Charge-Transfer Lanthanide Oxide Promoters for Enhanced Photocatalytic Ammonia Synthesis

Lanthanide metals possess multiple oxidation states, being emerging as a frontier toward the nitrogen fixation, yet the knowledge regarding their photocatalytic mechanism and active sites is very limited. Herein, a series of LnOy/MoS2 (Ln = La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu) photocatalysts for nitrogen fixation are successfully designed and synthesized. The experimental results demonstrate that the load of LnOy redox promoters (Ln = Ce, Eu or Tb, the following is also) significantly increases the effective reaction-active sites and promotes the separation and transfer of carriers, thereby improving photocatalytic performance. The visible-light-driven nitrogen fixation activities of LnOy/MoS2 composites are significantly enhanced, achieving remarkable rates of 342.8 μmol g⁻¹ h⁻¹ for CeOy/MoS2, 369.1 μmol g⁻¹ h⁻¹ for EuOy/MoS2, and 457.3 μmol g⁻¹ h⁻¹ for TbOy/MoS2, which are substantially higher than that of pristine MoS2 (46.1 μmol g⁻¹ h⁻¹). Theoretical calculations reveal that LnOy loading promote the adsorption and activation of N₂ molecules, with the Tb site exhibiting the strongest adsorption capacity (ΔG=1.46 eV) and superior electron transfer efficiency, as confirmed by PL spectroscopy and photocurrent response analysis. This work provides fundamental insights into the role of lanthanide oxides in regulating photocatalytic nitrogen activation and offers a strategic framework for designing high-performance lanthanide-based catalysts.