Defect engineering and 2D/2D coupling in Mn- and B-doped BiVO4 and Ti3C2 nanostructures

Doping is an effective method that modulates the electronic and optical properties of semiconductor nanomaterials through the addition of foreign atoms. In this work, bismuth vanadate (BiVO4) and titanium carbide (Ti3C2) MXene nanosheets were synthesized through facile solution processes. To elucidate the roles of defect engineering and 2D/2D interfacial coupling, a series of systems including Mn-BiVO4, B-Ti3C2, Ti₃C₂/BiVO4, Mn-BiVO4/Ti3C2, BiVO4/B-Ti3C2, and Mn-BiVO4/B-Ti3C2 were synthesized and characterized by XRD, FTIR, FESEM, and EDX. DRS results reveal that Mn and B doping, as well as the construction of the heterostructure, lower the optical band gap from 2.6 eV (pristine BiVO4/Ti3C2) to 2.4 eV (Mn-BiVO4/B-Ti3C2) and cause a redshift of ~30 nm in the absorption edge. XRD analysis confirms a lattice contraction of 0.41 Å in BiVO4 due to Mn doping and an expansion of 2.87 Å in Ti3C2 layers upon B doping. These controlled defect states and 2D/2D interfaces enhance charge separation and photoactivity, demonstrating the potential of Mn-BiVO4/B-Ti3C2 for photo-driven redox applications such as hydrogen evolution.