Ammonia synthesis at low temperatures

Density functional theory (DFT) calculations of reaction paths and energies for the industrial and the biological catalytic ammonia synthesis processe s are compared. The industrial catalyst is modeled by a ruthenium surface, while the active part of the enzyme is modeled by a MoFe6S9 complex. In con trast to the biological process, the industrial process requires high tempe ratures and pressures to proceed, and an explanation of this important diff erence is discussed. The possibility of a metal surface catalyzed process r unning at low temperatures and pressures is addressed, and DFT calculations have been carried out to evaluate its feasibility. The calculations sugges t that it might be possible to catalytically produce ammonia from molecular nitrogen at low temperatures and pressures, in particular if energy is fed into the process electrochemically. (C) 2000 American Institute of Physics . [S0021-9606(00)70911-1].