Accelerated electron and mass transfer through constructing H₂WO₄/Ti₃C₂/g-C₃N₄ Z-scheme photocatalyst for environmental remediation

The catalytic efficiency of photocatalysts highly depends on electron transport and mass transfer. Herein, we designed and prepared an effective H₂WO₄/Ti₃C₂/g-C₃N₄ (HTC) Z-scheme heterojunction through interfacial engineering strategy. The results manifested that 97.4% of Cr(VI) (80 μM, 50 mL) could be removed by HTC heterojunction within 10 min under visible light irradiation. The reduction rate constant of Cr(VI) for H₂WO₄/g-C₃N₄ (HC) heterojunction increased by a factor of 21 after introducing the conductive Ti₃C₂. Moreover, 96% of tetracycline (TC, 10 mg L⁻¹, 50 mL) could be degraded by HTC heterojunction within 30 min. The electronic conductivity and ionic diffusion coefficient of HC heterojunction increased by a factor of 64 and 1064 after adding Ti₃C₂, respectively. This result indicated that the introduction of highly conductive Ti₃C₂ significantly improved the electron and mass transfer of the heterojunction. Meanwhile, the HCT heterojunction displayed favorable photocurrent, and keep excellent photostability during the long-term test. Moreover, density functional theory (DFT) calculations demonstrated that the internal electric field (IEF) from g-C₃N₄ to H₂WO₄ in HCT heterojunction promotes the combination of the photoinduced electrons in the H₂WO₄ conduction band (CB) with photoinduced holes in the g-C₃N₄ valence band (VB), thus accelerating the charge transfer in the HCT Z-scheme heterojunction. The antibacterial efficiency of HTC heterojunction against E. coli and S. aureus could reach up to 98.4% and 99.7%, respectively. The degradation intermediates and the potential degradation mechanism of TC were analyzed and proposed based on the results of HPLC-MS analysis. Moreover, the toxicity of TC and degradation intermediates were estimated by Toxicity Estimation Software (T.E.S.T.) based on quantitative structure-activity relationship (QSAR). This work provided a valuable guideline for designing the effective MXene-based Z-scheme heterojunction for environmental remediation.