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 W18O49 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 W18O49 but also serves as a site for N2 adsorption and activation. Strategic doping of Co into W18O49 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 σg orbital of N2, which in turn promotes the migration of electrons from the Co 3d orbitals to the π* orbitals of the N2 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–W18O49 with the optimal Co-doping amount reaches 64.3 μmol gcat–1 h–1, which is approximately twice that of W18O49. The enhancement of the photocatalytic nitrogen fixation performance of the material through a Co-doping strategy holds broad application prospects.