Tuning Active Sites and Energy Band Structure of Nanowire-Based W ₁₈ O ₄₉ via Co-Doping for Efficient Photocatalytic Nitrogen Fixation

Active sites and the energy band structure of the catalyst are crucial in the photocatalytic nitrogen fixation process. In this study, we implemented a doping strategy to incorporate cobalt (Co) atoms into urchin-like W 18 O 49 nanostructures self-assembled from ultrathin nanowires. Both density functional theory calculations and experimental results demonstrate that Co-doping not only changes the energy band structure of W 18 O 49 but also serves as a site for N 2 adsorption and activation. Strategic doping of Co into W 18 O 49 significantly reduces the bandgap energy, thereby enhancing the excitation of photogenerated electrons. In addition, the d orbitals of the Co atoms are endowed with the capacity to accept electrons from the σ g orbital of N 2, which in turn promotes the migration of electrons from the Co 3d orbitals to the π* orbitals of the N 2 molecule, leading to activation of the nitrogen triple bond (N≡N). Under the combined effect of energy band modulation and active site introduction, the photocatalytic nitrogen fixation yield of Co–W 18 O 49 with the optimal Co-doping amount reaches 64.3 μmol g cat –1 h –1, which is approximately twice that of W 18 O 49 . The enhancement of the photocatalytic nitrogen fixation performance of the material through a Co-doping strategy holds broad application prospects.