La-loaded BiOBr enhances photocatalytic nitrogen fixation activity by reducing energy barriers for ammonia release

Rare earth element-loaded photocatalysts represent a promising alternative to the Haber-Bosch process for photocatalytic nitrogen reduction reactions (NRR). However, the underlying catalytic mechanisms remain insufficiently elucidated. In this work, lanthanum (La)-loaded bismuth oxybromide (BiOBr) nanoflower-like spherical photocatalyst was employed as a model system to investigate the mechanistic role of rare-earth metal La in photocatalytic nitrogen fixation. Characterization results indicate that La 3 + incorporate into the BiOBr lattice, likely preferentially near or influencing the electronic environment of the pre-existing oxygen vacancies (OVs). Combined with density-functional theory (DFT) calculations, it is shown that the introduction of La accelerates the subsequent steps: reducing the energy barriers for N hydrogenation (N→NH) and NH 3 desorption (*NH 3 →NH 3 ), facilitating both H addition to N and NH 3 release. La-loaded BiOBr (xLBOB) exhibits enhanced photocatalytic nitrogen fixation performance, with 0.2LBOB (0.2 wt% La) showing the highest ammonia yield. This study provides theoretical insights for designing rare earth-modified photocatalytic nitrogen fixation materials via local electron modulation and elucidates the reaction mechanism in depth.