3D dendritic hierarchically gradient nanoflowers in situ grown on conductive substrates for efficient hydrovoltaic power generation

Abstract

Hydrovoltaic power generators (HPGs) that continuously produce electricity through the interactions between water molecules and surface-charged pores/channels constitute a promising sustainable power generation strategy. However, current hydrovoltaic materials are hindered by inadequate power generation due to the selectivity–permeability trade-offs and the unclear structure–activity relationships between the pore/channel structure and the resulting electrical performance. In this study, an efficient water-droplet-induced HPG was developed using three-dimensional dendritic hierarchically graded nanoflowers grown in situ on the bottom electrode. The nanoflowers formed by the self-assembly of nanocells composed of nanorods featured an increased surface area and hierarchical macro/meso/microporosities that achieved synergistic high ionic selectivity and permeability. The in situ preparation of nanoflowers also facilitated their robust contact with the bottom electrode. Consequently, a single water droplet (20 μL) produced an open-circuit voltage of 600 mV and a high short-circuit current density of 45 μA cm⁻², approximately twice that of other hydrovoltaic materials. By leveraging the tunable porous structure with a precisely controlled average pore size spanning a broad range (20 nm–3.77 μm), the intricate correlation between the pore structure and the device performance was elucidated. Multifunctional self-powered sensing platforms, including an intelligent ultraviolet light alarm, a wearable breath-monitoring mask, and a non-contact human–machine interface were demonstrated. The proposed hierarchical-gradient nanoflower structure provides a new paradigm for constructing high-performance hydrovoltaic materials.