MXene mediated layered 2D-2D-3D g-C₃N₄@Ti₃C₂T@WO₃ multijunctional heterostructure with enhanced photoelectrochemical and photocatalytic properties

The fabrication of a MXene-based 2D-2D-3D g-C₃N₄@Ti₃C₂@WO₃ ternary hybrid photocatalyst was achieved via a facile ultrasonic-assisted and calcination synthetic approach. 2D Ti₃C₂T_x MXene nanosheets were integrated into the composite to facilitate efficient charge transfer and separations via a synergistic coupling effect. The layered 2D nanosheet structures are well known to exhibit larger contact interfaces with rapid charge transfer, hence the 2D materials are employed in this study. Meritorious photoelectrochemical properties were obtained for the g-C₃N₄@Ti₃C₂@WO₃ multijunction photocatalyst in comparison with pristine WO₃, g-C₃N₄ and the g-C₃N₄@WO₃ Z-Scheme, owing to the presence of highly conductive Ti₃C₂T_x. The pristine materials exhibit weak photocurrent signals relative to their corresponding heterostructures, which suggest a rapid decay character compared to the multijunction photocatalyst. Multiple charge transfer mechanisms and band alignments were proposed. The fabricated multijunction heterostructure couples Z-scheme and a Schottky-junction charge transfer mechanism. Enhanced electron migrations and light harvesting efficiency were observed using linear sweep voltammetry under visible light irradiation. High carrier concentrations (N_D=17.49 × 10²¹ cm⁻³) and a more positive flat band (V_FB=2.52 V vs. Ag/AgCl) are observed on Mott–Schottky analysis for 7wt% g-C₃N₄@Ti₃C₂@WO₃, as a result, a low overpotential is required to initiate the photocatalytic reactions. This study outlines an insight into the photoelectrochemical properties of non-noble metal multijunction heterostructures together with their synergistic coupling effects towards efficient charge transfer and separations.