Photocatalytic degradation of antibiotic and hydrogen production using diatom-templated 3D WO_3-x@mesoporous carbon nanohybrid under visible light irradiation

Synthesis of highly efficient 3D photocatalysts offers unique abilities for hydrogen production and chemical conversion to find a solution for energy shortage and environmental pollution issues. However, current strategies for production of ordered nanohybrid photocatalysts usually involve complex procedures and the use of expensive templates, which limit their practical applications. In this work, 3D WO_3-x@mesoporous carbon photocatalyst was fabricated through one-pot evaporation-induced self-assembly (EISA) process using Cyclotella sp. as natural template. During heat-treatment, the precursor of carbon could partially reduce tungsten oxide under N₂ atmosphere leading to the embedding of WO_3-x in conductive mesoporous carbon structure. The diatom templated WO_3-x@mesoporous carbon (DT-WO_3-x@MC) nanohybrid exhibited high surface area (195.37 m² g⁻¹) and narrowed band gap (2.67 eV). Integration of tungsten oxide with mesoporous carbon and formation of oxygen vacancies enhanced the absorption of visible light using DT-WO_3-x@MC and limited the recombination of electron-hole pairs. 98.7% of cefazolin (CFZ) degradation efficiency and 85.5% of total organic carbon (TOC) removal efficiency were observed within 90 and 180 min under visible light irradiation, respectively. Scavenger quenching tests and electron spin resonance (ESR) analysis demonstrated thatO₂^•− played a main role in photocatalysis. CFZ degradation pathway was proposed via identification of conversion intermediates using GC-MS analysis. Photocatalytic hydrogen production rates of the pure WO₃ and the DT-WO_3-x@MC nanohybrid were determined as 746 and 1851 μmol g⁻¹ h⁻¹, respectively. This study presented a way to develop a high-performance and stable photocatalyst using diatom frustules as natural template which works under practical conditions for environmental remediation and energy production.