Asymmetric Carbon‐Film Hydrovoltaic Generators With Work‐Function‐Correlated Output in Liquid‐Water and Hydrogel‐Assisted Moisture Operation

ABSTRACT Hydrovoltaic energy harvesting offers a promising approach for self‐powered electronics, but practical applications remain limited by insufficient output performance, challenges in scalable integration, and incomplete mechanistic understanding. Here, asymmetric carbon‐film hydrovoltaic generators with work‐function‐correlated output are reported for both liquid‐water and hydrogel‐assisted moisture operation. A single liquid‐water carbon‐film hydrovoltaic generator (C‐HEG) delivers ≈1.1 V and 450 µA cm − 2 , while a hydrogel‐assisted carbon‐film moisture‐electric generator (C‐MEG) delivers ≈1.0 V and 350 µA cm − 2 under ambient humidity. Modular integration scales the voltage up to ≈92 V and enables milliampere‐level output currents, demonstrating the feasibility of scalable energy harvesting and power supply for small electronics. Quantitative UPS/KPFM analyses, together with comparative equivalent‐circuit modeling, reveal a consistent correlation between the initial output voltage and the work‐function contrast, indicating that work‐function contrast can serve as a measurable descriptor of electronic asymmetry. The observed output is associated with the coupled effects of electronic asymmetry, water‐mediated interfacial charging/electric‐double‐layer development, and hydrated‐ion transport. These results suggest that electronic‐structure‐guided interfacial engineering may assist the optimization of asymmetric carbon‐film hydrovoltaic generators for scalable self‐powered and wearable electronics.