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

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.