Hierarchically Converged Defect Engineering with 2-Dimensional Black Phosphorus/MXene Sequence for Sensitive Photoelectrochemical-Electrostatic Sensors

The function-integrated sensors have harvested increasingly vital across diverse applications, especially in the field of smart wearables, yet optimizing the synergy between electrostatic and light signals in photoelectrochemical (PEC) systems remains a critical challenge. Here, we fabricate a hierarchical ZnO/Bi₂O₃/BiOCl/black phosphorus (BP)/MXene (Ti₃C₂T <i>_x</i> ) heterostructure and develop a PEC sensor tailored for electrostatic coupling and surface electromyography (sEMG) detection. Sequential integration of 2-dimensional (2D) BP and Ti₃C₂T <i>_x</i> precisely repairs defects in the 3D ZnO/Bi₂O₃/BiOCl framework, enhancing electrode contact area and forming multidimensional heterostructures that markedly boost electron-hole separation. Under illumination or ambient electrostatic field (AEF) stimulation, the composite electrode outperforms its pristine counterpart, achieving a photocurrent of 20.46 μA cm^-2 under 30-W blue light, which is 2.4 times higher than the device without the 2D layers. A synergistic AEF-light effect further enhances carrier transport, amplifying AEF detection sensitivity. These results highlight defect engineering as a robust strategy for advancing PEC performance in PEC applications and enable a light-assisted sEMG sensor with marked signal improvement.