Heterojunction-Architected Bismuth Titanate Nanobelts: Ternary-Phase Engineering for Enhanced Photocatalytic Hydrogen Evolution

We report the synthesis of heterojunction-architected bismuth titanate nanobelts obtained by mild reductive treatment of hydrothermally synthesized bismuth titanate (BT). The resulting defective material (BTD) comprises metallic Bi, Bi₂Ti₂O₇, and Bi₄Ti₃O₁₂, generating a ternary-phase heterostructure with interfacial defects. Structural and surface analyses by STEM, XRD, XPS, and cathodoluminescence, together with EIS under illumination, indicate that phase coupling and defect formation improve charge transport in BTD. In photocatalytic H₂ evolution from water/methanol under UV irradiation, BTD reaches 382.89 μmol g⁻¹ cat h⁻¹ at 1 h, outperforming BT (179.36 μmol g⁻¹ cath⁻¹) and TiO₂ (209.74 μmol g⁻¹ cat h⁻¹). At 4 h, BTD continues with the highest H₂ production. These results demonstrate that ternary phase engineering and defect-mediated heterojunction formation promote charge separation and photocatalytic hydrogen evolution in bismuth titanate nanobelts.