Exploring Adsorption and Reactivity of NH3 on Reduced Graphene Oxide

Sensors based on graphene and functionalized graphene are emerging as the state of the art for detecting extremely small quantities of target molecules under realistic working conditions with high selectivity. Although some theoretical work has emerged to understand such adsorption processes (Tang and Cao J. Phys. Chem. C 2012, 116, 8778; Leenaerts et al. Phys. Rev. B 2008, 77, 125416; Tang and CaoJ. Chem. Phys. 2011, 134, 044710), little experimental evidence detailing the dynamics of the adsorption and resulting surface species has been reported. Here, we study the adsorption of NH3 on reduced graphene oxide (RGO) using in situ infrared (IR) microspectroscopy performed under realistic working conditions (i.e., ambient pressure), along with density functional theory (DFT) calculations to support experimental observations. Conclusions drawn from experiment and theory reveal the presence of various surface species that impact the conductivity of the substrate at varying rates. The species arising from adsorption and interactions between NH3 and RGO include molecularly physisorbed NH3, as well as chemisorbed fragments such as NH2, OH, and CH due to dissociation of NH3 at defects and epoxide groups.