The invention discloses
aerogel with a vertical
porosity gradient structure and a preparation method and application thereof.The method comprises the steps that firstly, a
cellulose raw material is pulpified and purified, a uniform substrate is provided for structure regulation, and
moisture response performance is stabilized; secondly, a TEMPO / NaBr / NaClO
system is adopted for
catalytic oxidation of the
cellulose surface, hydrophilic groups such as carboxyl are introduced, the hygroscopicity and
ionic conductivity of the fibers are improved, a high-specific-surface-area
fiber network is formed through filter-pressing homogenization treatment, local resistance difference is reduced, and output
voltage and current are stabilized; then, directional freezing induces the nanofibers to be vertically arranged, a vertical pore gradient structure is constructed,
moisture is rapidly diffused to form a stable
humidity gradient field, ions are driven to continuously and directionally migrate, and the
energy conversion efficiency and the output power stability are improved; finally, the
binding force between the fibers is enhanced through
metal salt crosslinking, a three-dimensional network is formed, the
mechanical strength and swelling resistance are improved, structural collapse is prevented, it is ensured that the device is reliable for a long time in a humid environment, and the service life is prolonged.