Hierarchical design of NiFe₂O₄@BN/g-C₃N₄ Z-scheme heterojunctions for enhanced photocatalytic detoxification of tetracycline: Optimization of key parameters and H₂ evolution

Developing highly efficient bifunctional photocatalysts with improved charge separation and ample active sites is a significant challenge in environmental remediation and sustainable hydrogen (H₂) production. To tackle these energy and environmental issues, we synthesized highly efficient bifunctional NiFe₂O₄ (NF), h-BN/g-C₃N₄ (CBN), and NiFe₂O₄@BN/g-C₃N₄ (NF@CBN) composite photocatalysts using a surfactant-assisted hydrothermal method. Comprehensive characterization confirmed that NF nanoparticles were successfully integrated into CBN nanosheets to create robust composite structures. Among the synthesized catalysts, the NF@CBN-2 composites demonstrated excellent photocatalytic performance, achieving 98 % and 94 % tetracycline (TC) removal rates within 120 min under solar and visible light, respectively. Moreover, it showcased an outstanding hydrogen evolution rate of 1639 μmol h⁻¹g⁻¹ in 1 h, and the apparent quantum yield (AQY) is approximately 26.0 % at 420 nm. Systematic optimization of reaction conditions and mechanistic studies revealed that the superoxide radical (^•O₂⁻) plays a crucial role in the degradation process. The enhanced photocatalytic efficiency of NF@CBN-2 results from improved charge separation, large surface area, abundant active sites, and synergistic interactions within the composite. Based on these findings, a Z-scheme photocatalytic mechanism is proposed to explain its superior activity. Furthermore, the NF@CBN composite displays excellent stability, underscoring its potential for practical applications in industrial wastewater treatment and renewable energy production.