Multilayered Platinum Nanotube for Oxygen Reduction in a Fuel Cell Cathode: Origin of Activity and Product Selectivity

The practical usages of proton exchange membrane fuel cells from the economical perspective is closely related to the development of catalysts with reduced platinum loading for improved oxygen reduction reaction (ORR) activity. For this, a multilayered platinum nanotube enclosed by (111) and (100) facets has been modeled and studied for ORR activity using the density functional theory calculations. The stability of the nanotube is verified through energetic, thermal, and dynamic stability calculations. Activation barrier analysis shows that the rate-determining steps (O2 dissociation and OH formation) are highly improved over the nanotube surface. We find that four-electron reduction pathway (for H2O formation) is favored over two-electron reduction (for H2O2 formation) for the nanotube catalyst, which ensures excellent product selectivity (H2O vs H2O2). The excellent catalytic activity and product selectivity of the nanotube can be attributed toward the favorable adsorption energies of ORR intermediates, as the adsorption energies of key ORR intermediates are reported to be excellent descriptors for ORR activity. Therefore, the platinum nanotube can be a potential electrode material for fuel cell and other related applications.