Effect of Ammonia on Pt, Ru, Rh, and Ni Cathodes During the Alkaline Hydrogen Evolution Reaction

The effects of ammonia on the hydrogen evolution reaction (HER) with Pt, Rh, Ru, and Ni have been investigated using electrochemical methods. The activity of the catalysts for HER, in the presence of ammonia follows the trend Rh > Pt > Ru > Ni. Pt and Ru exhibit a decrease in the activity toward HER Cyclic voltammetric (CV) studies show that the presence of ammonia results in weaker metal-hydrogen underpotential deposition (M-H-upd) bonds. In addition, the activity of HER on Pt and Ru is retarded in the presence of ammonia, supporting the theory that the activity for HER is higher on the metal surface with H-upd than on the bare metal. On the contrary, the activity for HER on Rh surface in the presence of ammonia is enhanced, suggesting the M-H-upd bond is a barrier to the HER CV for Ni in the presence of ammonia shows a Ni(OH)(2) reduction peak. However, the overpotentials for HER on Ni are very high such that no significant difference is observed in the activity of HER.