A hybrid structure gas sensor of reduced graphene oxide (RGO) decorated graphene (RGO-Gr) is designed for ultra-low concentration ammonia detection. The resistance value of the RGO-Gr hybrid is the indicator of the ammonia concentration and controlled by effective charge transport from RGO to graphene after ammonia molecule adsorption. In this hybrid material, RGO is the adsorbing layer to catch ammonia molecules and graphene is the conductive layer to effectively enhance charge/electron transport. Compared to a RGO gas sensor, the signal-to-noise ratio (SNR) of the RGO-Gr is increased from 22 to 1008. Meanwhile, the response of the RGO-Gr gas sensor is better than that of either a pristine graphene or RGO gas sensor. It is found that the RGO reduction time is related to the content of functional groups that directly reflect on the gas sensing properties of the sensor. The RGO-Gr gas sensor with 10 min reduction time has the best gas sensing properties in this type of sensor. The highest sensitivity is 2.88% towards 0.5 ppm, and the ammonia gas detection limit is calculated to be 36 ppb.

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The electrocatalytic applications of traditional polyimide film and carbon nanomaterials are hindered due to a shortage of three-dimensional hierarchical conductivity and porous structure. Herein, a novel polyimide-based electrode based on a highly efficient palladium nanocatalyst embellished three-dimensional reduced graphene oxide/polyimide foam (Pd/3D RGO@PI foam, signed PRP) toward H 2 O 2 electroreduction was designed and prepared through thermal foaming procedure, followed by facile dip-drying method and electrodeposition. As expected, such a binder-free, 3D hierarchical structure PRP electrode presented high catalytic property, good stability, as well as low activation energy toward H 2 O 2 electroreduction during the electrochemical measurement period. The PRP electrode showed a reduction current density of 810 mA•cm −2 at −0.2 V (vs Ag/AgCl) in 2.0 mol•L −1 H 2 SO 4 and 2.0 mol•L −1 H 2 O 2 . Moreover, the PRP electrode also illustrated good reproducibility and repeatability. Reproducibility presented almost 95.8% of the initial current density after 1000 cycles test. Also, the activation energy of H 2 O 2 electroreduction on 3D PRP electrode was 21.624 kJ•mol −1 . Benefiting from the 3D hierarchical structure and efficient catalyst, the PRP electrode exhibited excellent electrocatalytic performance and was considered to be a potential candidate material for fuel cells.

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