Dual properties of a hydrogen oxidation Ni-catalyst entrapped within a polymer promote self-defense against oxygen

The Ni(P₂N₂)₂ catalysts are among the most efficient non-noble-metal based molecular catalysts for H₂ cycling. However, these catalysts are O₂ sensitive and lack long term stability under operating conditions. Here, we show that in a redox silent polymer matrix the catalyst is dispersed into two functionally different reaction layers. Close to the electrode surface is the "active" layer where the catalyst oxidizes H₂ and exchanges electrons with the electrode generating a current. At the outer film boundary, insulation of the catalyst from the electrode forms a "protection" layer in which H₂ is used by the catalyst to convert O₂ to H₂O, thereby providing the "active" layer with a barrier against O₂. This simple but efficient polymer-based electrode design solves one of the biggest limitations of these otherwise very efficient catalysts enhancing its stability for catalytic H₂ oxidation as well as O₂ tolerance.