Density functional theory calculations are carried out to investigate the adsorption characteristics of methane (CH4), carbon dioxide (CO2), hydrogen (H-2), hydrogen sulfide (H2S), nitrogen (N-2), and oxygen (O-2) on the surface of pyridine-like nitrogen doped graphene (PNG) as well as noble metal (Rh, Pt, Pd) decorated PNG to elaborate their potentials as gas sensors. The adsorption intensities of biogas on noble metal (Rh, Pt, Pd) decorated PNG are in the order of O-2 > H2S > N-2 > CH4 > CO2 > H-2, which are corresponded to the order of their sensitivity on surface. Compared with biogas adsorption on pristine PNG, there exist higher adsorption ability, higher charge transfer and higher orbital hybridization upon adsorption on noble metal (Rh, Pt, Pd) decorated PNG. Consequently, the noble metal (Rh, Pt, Pd) decorated PNG can transform the existence of CH4, CO2, H-2, H2S, N-2, and O-2 molecules into electrical signal and they could potentially be used as ideal sensors for detection of biogas in ambient situation. (C) 2017 Elsevier B.V. All rights reserved.