Noble-Metal-Free Reduced Graphene Oxide Platforms for Room-Temperature H2 Sensing in High-Humidity Conditions

F. SCHIPANI; J. PUIG; G. M. MORALES; C. MACCHI

Journal of Materials Science: Materials in Electronics

Springer

Año: 2023

Reduced grapheneoxide (rGO) sensors - free from noble metal nanoparticles - were prepared and testedat room temperature (21 °C) against hydrogen (H2) in high humidityconditions (above 90% r.h.). The rGO material wasobtained through a simple chemical/thermal protocol from graphene oxide (GO) asthe starting material, using ascorbic acid as the reducing agent. The degree ofreduction of GO was tuned by modifying the chemo-thermal conditions, whichallowed shaping the sensing response. The latter was demonstrated to scale withthe sp2 carbon (Csp2) content of the rGO structure, whichvaried from ~40%-Csp2for the least-reduced sample to ~70%-Csp2 for the highest-reducedmaterial. Current-voltage measurements revealed the influence of the reductionon the electronic conduction mechanisms, evidencing a shift from a strongnon-linear behavior (with a component characteristic of a space charge limitedconduction mechanism, SCLC) to a pure ohmic-like response as the reduction ofGO proceeded. In order toevaluate the selectivity of the sensors to the target molecule, differentoxidizing and reducing gases other than H2 (CO,CO2 and NO2) were also tested. The highest-reducedsample showed a superior response when exposed to a range of H2 concentrationsin an atmosphere with humidity levels above 90% r.h. In these conditions, anegligible cross-sensitivity to CO, CO2 and NO2 wasachieved. For the top-performance sensor, the response (t66) andrecovery (trec) times were calculated to be 72 s and 374 s (at 0.05%H2), respectively, with a sensitivity of 0.7% and an estimateddetection limit of 2.5 ppm of H2.