Mixing thermodynamics and electronic structure of the Pt1−xNix (0 ≤ x ≤ 1) bimetallic alloy

The development of affordable bifunctional platinum alloys as electrode materials for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains one of the biggest challenges for the transition towards renewable energy sources. Yet, there is very little information on the optimal ratio between platinum and the transition metal used in the alloy and its impact on the electronic properties. Here, we have employed spin-polarised density functional simulations with long-range dispersion corrections [DFT–D3–(BJ)], to investigate the thermodynamics of mixing, as well as the electronic and magnetic properties of the Pt_1−xNi_x solid solution. The Ni incorporation is an exothermic process and the alloy composition Pt_0.5Ni_0.5 is the most thermodynamically stable. The Pt_0.5Ni_0.5 solid solution is highly ordered as it is composed mainly of two symmetrically inequivalent configurations of homogeneously distributed atoms. We have obtained the atomic projections of the electronic density of states and band structure, showing that the Pt_0.5Ni_0.5 alloy has metallic character. The suitable electronic properties of the thermodynamically stable Pt_0.5Ni_0.5 solid solution shows promise as a sustainable catalyst for future regenerative fuel cells.

Density functional theory simulations complemented by force-field based calculations show that the bimetallic Pt_0.5Ni_0.5 equilibrium composition is highly ordered at room conditions.