Na⁺-doping induced synergistic oxygen vacancies and compressive strain for enhanced photocatalytic formaldehyde...

The efficiency of photocatalytic formaldehyde (HCHO) mineralization is often limited by insufficient adsorption and activation of O₂ and HCHO on conventional semiconductor surfaces. In this work, we demonstrate a 'kill two birds with one stone' strategy-Na⁺ doping in ZnWO₄-which simultaneously introduces oxygen vacancies and compressive lattice strain. This synergistic defect and strain engineering injects electrons into the W 5d orbitals, creating electron-rich W sites and shifting the d-band center upward. The resulting electronic structure enhances the adsorption and activation of both O₂ and HCHO, with adsorption energies reaching -2.08 eV and - 1.02 eV, respectively, significantly reducing the energy barrier of the rate-limiting formate oxidation step from -0.26 eV to -1.45 eV. Consequently, Na-ZnWO₄ achieves markedly improved reactive oxygen species generation, an 80.2% HCHO removal efficiency, and a high CO₂ yield under simulated solar light, greatly outperforming pristine ZnWO₄. This work demonstrates a co-regulation strategy for defects and strain via cation doping as an effective route toward high-performance photocatalytic materials.