Long-Lasting Hydrogen Evolution and Efficient Dew Harvest Realized via Electrospinning Polyvinylidene Fluoride Membrane on Hybrid Hydrogels

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.

Recent Development of Fibrous Hydrogels: Properties, Applications and Perspectives

Fibrous hydrogels (FGs), characterized by a 3D network structure made from prefabricated fibers, fibrils and polymeric materials, have emerged as significant materials in numerous fields. However, the challenge of balancing mechanical properties and functions hinders their further development. This article reviews the main advantages of FGs, including enhanced mechanical properties, high conductivity, high antimicrobial and anti-inflammatory properties, stimulus responsiveness, and an extracellular matrix (ECM)-like structure. It also discusses the influence of assembly methods, such as fiber cross-linking, interfacial treatments of fibers with hydrogel matrices, and supramolecular assembly, on the diverse functionalities of FGs. Furthermore, the mechanisms for improving the performance of the above five aspects are discussed, such as creating ion carrier channels for conductivity, in situ gelation of drugs to enhance antibacterial and anti-inflammatory properties, and entanglement and hydrophobic interactions between fibers, resulting in ECM-like structured FGs. In addition, this review addresses the application of FGs in sensors, dressings, and tissue scaffolds based on the synergistic effects of optimizing the performance. Finally, challenges and future applications of FGs are discussed, providing a theoretical foundation and new insights for the design and application of cutting-edge FGs.