Climate‐Adaptive High‐Performance Moisture‐Induced Electric Generator Utilizing Electric Double‐Layer Gradient

Abstract Water energy harvesting technologies provide a promising approach for harnessing ubiquitous water for clean, renewable energy generation. However, existing systems often rely on mechanical water movement, liquid water supplementation, or high‐humidity conditions, limiting their practical applications in fluctuating environments and wearables. Here, a self‐gradient hydrogel‐based moisture‐induced electric generator (SHMEG) is reported, formed by the self‐diffusion of pre‐gel solution on carbon blacks loaded knitted fabric and a pair of sliver electrodes, which can maintain high performance and flexibility under various environments. The main driving source of SHMEG is the electric double‐layer gradient formed at the hydrogel–carbon interface and the intrinsic properties of electrode. The SHMEG demonstrates a sustained voltage output of 0.75 V for 140 h and a current output of 15 µA at ≈75% RH under room temperature (≈25 °C). Benefitting from the high hygroscopicity, moisture retention, and temperature adaptability, SHMEG reliably delivers a stable electrical output of 0.5 V at 20% RH and 0.7 V at −10 °C. Moreover, SHMEG demonstrates versatility by powering small electronics and functioning as a strain sensor with up to 300% stretchability. This work represents a significant advance in moisture‐induced energy harvesting, expanding its applicability to a broader range of environments and wearables.