Density Functional Theory Analysis of Metal/Graphene Systems As a Filter Membrane to Prevent CO Poisoning in Hydrogen Fuel Cells

Hydrogen fuel cells are a very promising potential replacement for internal combustion engines. However, their current use is limited by carbon monoxide poisoning of the platinum anode catalyst that occurs when CO enters the cell in the H-2 feed gas. A novel new solution to this problem is the addition of a metal/graphene filter membrane exterior to the cell. This membrane will remove CO from the feed gas, allowing reduced loading of the expensive Pt catalyst and increasing cell lifetime. In the current work, density functional theory (DFT) was used to analyze graphene membranes containing nickel, copper, platinum, and iridium/gold atoms. The binding energy of the metal to the graphene was measured for a lone system and in the presence of CO and H-2 to predict its durability. The binding energy of CO and H-2 to metal was also measured to estimate its efficiency. All systems were analyzed using natural bond orbitals (NBOs). It was found that copper is a poor choice for use in membranes in all respects. Nickel systems show the most promise: they have a consistent metal/graphene binding energy when feed gas molecules are introduced. In addition, although CO binding is strong to Ni, Pt, and Jr/Au, nickel systems show the weakest interaction with H-2. NBO analysis of these systems shows that metal orbitals are the most involved in bonding.