Nitrogen plasma-engineered carbon/paper platform for hybrid moisture-activated power generation, humidity sensing, and actuation

Utilizing ambient humidity for sustainable power generation at cost-effective, flexible platforms remains a major challenge in materials science and renewable energy technology. Purely non-Faradaic moisture-enabled generators (MEGs) have most often, though not universally, delivered sub-volt energy outputs. This work presents a multifunctional smart-paper system that achieves voltages above 1 V by integrating moisture-activated ion transport with a sustained Al-carbon galvanic couple. By pairing a nitrogen-plasma-engineered carbon black cathode with an asymmetric aluminum anode across a hygroscopic paper substrate, the platform delivers a transient open-circuit peak of 1.47 V that decays to a steady-state plateau of 1.33 V sustained for over six hours at 70 %RH, with a drift of 0.97 mV h⁻¹, approximately twelve times lower than that of an untreated-carbon control device measured in a single side-by-side comparison. The same device also serves as a self-powered respiratory humidity sensor and as a dual-mode actuator (passive hygromorphic plus externally powered electrothermal). The plasma-functionalized carbon cathode thus provides a lab-batch-fabricable route to a hybrid moisture-activated platform combining stable voltages above 1 V, multifunctional sensing and actuation, while the deliverable power density remains in the nanowatt-per-square-centimeter range.