Hydrogen bonding-mediated α-Fe2O3-decorated rGO hybrids for dual-mode humidity sensing and multi-scenario applications

The development of self-powered humidity sensors featuring rapid response, low hysteresis, and dual-mode signal output is highly anticipated in healthcare monitoring, wearable electronics and human-machine interaction. Here, we present a hydrogen bonding-mediated self-assembly strategy to synthesize α-Fe 2 O 3 -decorated reduced graphene oxide (Fe 2 O 3 -rGO) hybrids for high-performance dual-mode humidity sensing. In impedance mode, the sensor demonstrates a broad detection range (11–98 % RH), a response value of 71.1 at 98 % RH, fast response/recovery times (1 s/5 s), and minimal hysteresis (3.7 %). The sensing mechanism, elucidated through complex impedance spectroscopy and water adsorption isotherms, reveals synergistic proton transport and p-n heterojunction effects at the α-Fe 2 O 3 -rGO interface. Notably, the sensor also operates in a self-powered mode, generating an ultrahigh output voltage (1.1 V at 98 % RH) through humidity-triggered galvanic reactions, enabling capacitor charging and light-emitting diode (LED) driving. Practical applicability is demonstrated through real-time respiratory monitoring, Morse code communication, and non-contact finger motion tracking, underscoring its utility in wearable electronics. This work provides a scalable and cost-effective approach to designing multifunctional humidity sensors with broad applicability in smart systems and healthcare.