Graphene-based conductometric monitoring of hydrogen purity (Proof of Concept)

Abstract

Hydrogen (H₂), a clean, safe, and eco-friendly energy source, is pivotal in addressing global energy challenges. However, its production involves separating pure H₂ from compounds such as water (H₂O) and methane (CH₄), where even trace impurities critically affect the performance of proton exchange membrane fuel cells. In this study, for the first time, a conductometric gas sensor based on few-layered graphene powder (FLGP) was applied to detect impurities in hydrogen. The sensor exhibited a remarkable response of ∼25 % to 100 ppm CH₄ at 50 °C, significantly outperforming many conventional metal-oxide sensors that require >200 °C. It also demonstrated detectable responses to 2 ppm CO₂ (4.3 %), 5 ppm O₂ (3.3 %), and 5 ppm N₂O (8.7 %) in H₂ atmosphere, meeting ISO14687 impurity thresholds. First-principles calculations revealed that the adsorption energy of a single CH₄ molecule on graphene (–0.20 eV) is approximately twice as strong as H₂ (–0.10 eV), and decreases further (–0.09 eV) in the presence of 10 H₂ molecules, confirming a competitive adsorption mechanism. This combined experimental–theoretical study provides the first proof of concept that pure graphene powders can serve as compact, low-temperature, and cost-effective sensors for hydrogen fuel purity monitoring, opening new horizons for safe and sustainable hydrogen energy technologies.