Environmental Aging and Operational Reliability of ZnO–Graphene Nanocomposites: Investigating Humidity-Induced Degradation, Thermal Cycling, and Long-Term Functional Stability

Abstract

The functional performance of ZnO–graphene nanocomposites is extensively documented under controlled laboratory conditions, yet their reliability under prolonged environmental and operational stress remains poorly characterized. This study addresses the gap between laboratory performance and real-world durability by investigating humidity-induced degradation, thermal stability, and long-term electrical reliability in ZnO–reduced graphene oxide (rGO) nanocomposites. The constituent phases exhibit fundamentally divergent humidity responses: ZnO, as an n-type semiconductor, decreases in resistance upon water adsorption due to protonic conduction, whereas rGO, being p-type, increases in resistance as water-derived electrons deplete holes . In the nanocomposite, however, the synergistic coupling between components suppresses these individual responses, with optimized compositions exhibiting minimal resistance variation at elevated humidity. Thermal stability is enhanced by ZnO incorporation, with precursor selection and morphology shown to critically influence the thermal resilience of graphene–ZnO composites. Long-term operational stability is governed by interfacial bonding quality rather than intrinsic material properties, with degradation rates correlating to the completeness of ZnO coverage on the rGO surface. The findings establish that compositional optimization for initial performance coincides with optimization for environmental reliability, providing rational design criteria for durable ZnO–graphene devices.