A systematic spin-polarized density functional theory (DFT) study of hydrogen interaction with pristine and Rh-decorated zigzag (8,0) single-walled carbon nanotubes (SWCNTs) was performed. The most stable decoration site for Rh atoms as well as atomic and molecular hydrogen adsorption inside and outside the SWCNT was studied. Hydrogen adsorption energy in Rh-decorated SWCNTs was improved compared to that of pristine nanotubes. In addition, Rh-decorated SWCNT systems present a magnetic moment. Density of states and work function (WF) were computed to study the bonding evolution and electronic structure. When hydrogen is considered on Rh-SWCNT and pristine SWCNT, the WF increased while band gap decreased compared to that of pristine SWCNT.Fil...