Piezoelectricity-Enhanced Photocatalytic Hydrogen Evolution via Switching Nanofibers to a Flat Structure and Construction of a Photoconductive Interface in Kelp-Shaped Hybrid Electrospun Membranes

Inspired by the efficient light-harvesting capability of kelp with a flat structure, a piezoelectricity-enhanced photocatalytic hydrogen evolution is realized by constructing kelp-shaped hybrid electrospun membranes to improve the separation efficiency of photogenerated charge carriers. During electrospinning, the addition of LiCl to the PVDF electrospinning solution triggers an inhomogeneous distribution of charges, inducing asymmetric stretching and transforming the nanofibers into a kelp-shaped structure. After that, a photoconductive polydopamine (PDA) layer is in-situ synthesized on the nanofiber surfaces. After deposition of g-C3N4@Pt nanosheets on the kelp-shaped PVDF membranes with a PDA interlayer, a second electrospun PVDF membrane with a regular round shape is coated on top to ensure the stability of g-C3N4@Pt nanosheets. The flat cross-section of PVDF nanofibers significantly enlarges the contact area between the nanofibers and g-C3N4@Pt nanosheets. The formed hydrogen bonds strengthen the interface interaction and improve conductivity. Therefore, the piezoelectric field generated by PVDF membranes can efficiently separate the photogenerated charge carriers from g-C3N4@Pt and prolong their lifetime. The hydrogen evolution is profoundly enhanced to 17,500 μmol g-1 h-1 under water flow, 11.8 times that of g-C3N4@Pt. Thus, kelp-shaped hybrid PVDF membranes are perfect for piezoelectric-photocatalytic hydrogen evolution under water flow and solar energy.