Faradaic Reversible Electrodes Enable Programmable High‐Power Hydrovoltaic Energy Harvesting Across Broad Ionic Environments

Harvesting energy from water evaporation through hydrovoltaic devices provides a sustainable approach to electricity generation and decentralized power solutions. However, practical performance remains limited by low-current outputs (<100 nA cm^-2) and operation restricted to low-ionic-strength conditions (<10^-3 M). Here, dual-function, mesh-structured core-shell Ag/AgX reversible electrodes are developed to construct high-current hydrovoltaic devices operable across diverse ionic environments. The in-situ-formed AgX shell mediates redox-driven interfacial ion-electron transduction, while the Ag core provides high-speed electronic pathways, synergistically promoting the efficient conversion of ionic migration into continuous electron flow. Leveraging the localized charge inversion effect, programmable electrical outputs in both magnitude and polarity are obtained further. By co-designing Ag/AgI electrodes with KI-based electrolytes, this device delivers a record-high current density of 26.0 µA cm^-2 sustained over 160 h with power density exceeding 3.9 mW m^-2, ≈260-fold higher current and ≈39-fold greater power than previously reported inert-electrode-based systems. Moreover, the solid-liquid interfacial charge inversion enables tunable ion transport and reconfigurable nanochannel selectivity, realizing programmable outputs over an extensive ionic-concentration window (10^-6-10⁰ M) and multiple ionic species. This strategy implements versatile energy-sensing systems capable of powering electronics and supporting diversified self-powered monitoring across natural and industrial water sources.