Sandwich-like Hybrid Electrospun Membrane-Based Efficient Hydrogen Evolution System by the Push-Pull Double Piezoelectric Effect Driven by Water Flow

An efficient photocatalytic hydrogen evolution is realized by a push-pull effect from the piezoelectricity of a flexible hybrid membrane introduced via the water flow energy. The flexible hybrid membrane possesses a sandwich-like structure, prepared by sequentially electrospinning poly(vinylidene fluoride) (PVDF), depositing graphitic carbon nitride with Pt atoms (g-C₃N₄@Pt), and again electrospinning PVDF. Due to the piezoelectric property of PVDF, the deformation of the obtained sandwich-like hybrid PVDF/g-C₃N₄@Pt/PVDF membrane triggers two electric fields with the same direction in the top and bottom PVDF membranes. Therefore, either electrons or holes photogenerated by g-C₃N₄@Pt are attracted to one electric field and repelled by another. This push-pull effect induces a directional movement of charge carriers, which not only eases the separation but also hinders the recombination. Based on this favorable effect and finite element simulations for stress distribution on the membrane, the position of the sandwich-like hybrid PVDF/g-C₃N₄@Pt/PVDF membrane is optimized. The hydrogen evolution rate strongly increases to 5401 μmol h^-1 g^-1 under water flow, which is 240% to that of g-C₃N₄@Pt nanosheets. Thus, the sandwich-like hybrid membrane with a push-pull effect is very suitable for hydrogen production in natural aqueous environments rich in water flow and solar energy, such as lakes and rivers.