Doping Effects on the Performance of Paired Metal Catalysts for the Hydrogen Evolution Reaction.

Metal heteroatoms dispersed in nitrogen-doped graphene display promising catalytic activity for fuel cell reactions such as the hydrogen evolution reaction (HER). Here we explore the effects of the dopant concentration on the synergistic catalytic behavior of a paired metal atom active site comprising Co and Pt atoms that have been shown to be particularly active catalysts in these materials. The metals are coordinated to six atoms in a vacancy of N-doped graphene. We find that the HER activity is enhanced with increasing N concentration, where the free energy of hydrogen atom adsorption ranges from 0.23 to -0.42 eV as the doping changes from a single N atom doped in the pore to fully doped coordination sites. The results indicate that the effect of N is to make the metal atoms more active toward H adsorption, presenting a means through which transition metals can be modified to make more effective and sustainable fuel cell catalysts.