Heterojunction Synergized Nanofluidic Ionic Diode for High‐Performance Hydrovoltaic Electricity Generation

Hydrovoltaic electricity generators have emerged as a promising strategy for harvesting low-grade environmental energy. Yet their output remains limited by inefficient charge separation, hydroxyl-induced electron trapping, and reverse current loss. Herein, we proposed a heterojunction synergized nanofluidic ionic diode concept to enhance HEG performance. Al-doped TiO₂ (ATO) was conformally deposited on vertically aligned Si nanowires (SiNWs) via atomic layer deposition to form a SiNWs/ATO heterojunction, where the built-in electric field facilitates the efficient separation of charge induced by evaporation-driven capillary flow. Simultaneously, a nanofluidic ionic diode is established between positively charged SiNWs/ATO nanochannels and the negatively charged porous CNT membrane, enabling rectified ion-selective transport. The synergistic effects of the heterojunction and nanofluidic ionic diode significantly promote both electron-hole separation and anion/cation selective transport. The SiNWs/ATO HEG achieves an updated recorded performance, delivering an open-circuit voltage of 1.0 V, a short-circuit current density of 71.0 µA·cm^-2, and a peak power density of 45.8 µW·cm^-2, approximately twice the highest values previously reported for HEGs. This work not only achieves a mechanistic co-optimization of charge separation and ionic transport induced by evaporation-driven capillary flow, but also offers a novel design strategy and practical framework to develop high-performance and durable HEG.