Density functional theory analysis of selective adsorption of AsH on transition metal-doped graphene.

The removal of AsH from synthesis gas is crucial to prevent methanol synthesis catalyst from poisoning. In this work, Ti-, Mn-, Fe-, Co-, Ni-, Cu-, and Ag-doped graphene were proposed and their adsorption capabilities for AsH and CO were investigated by DFT method. The optimized structures, adsorption energies, electron transfers, electron density difference, and density of states were thoroughly discussed. It was found that pristine graphene had a slight interaction with AsH or CO, while doping Ti, Mn, Fe, Co, Ni, and Ag could greatly facilitate the AsH or CO adsorption with the adsorption energies of - 0.95 to - 1.45 eV (AsH) and - 1.00 to 2.02 eV (CO). The partial density of states (PDOS) results showed that hybridizations between AsH orbitals, CO orbitals, and transition metals orbitals indicate that there were chemical interactions between them. The charge transfer and density of states (DOS) plots showed that AsH and CO have the same adsorption modes on transition metals-doped graphene. Among seven transition metals-doped graphene, Ni-doped graphene had the best selectivity for AsH but not for CO due to its larger adsorption energy discrepancy between AsH and CO than that of other transition metals-doped graphene, suggesting that Ni-doped graphene is a good candidate adsorbent for AsH removal in CO gas stream. Graphical abstract Seven transition metal (Ti, Mn, Fe, Co, Ni, Cu, Ag)-doped graphenes were investigated for AsH and CO adsorption by DFT method. Their most stable structure, adsorption energy, and electronic characters were thoroughly studied. The results showed that Ni-doped graphene was a good candidate for selective AsH adsorption.