Using site occupation disorder to build bulk structures of Ni1-xAlx

Abstract

Raney nickel shows potential as an electrocatalyst for the oxygen evolution reaction (OER). However, the catalytic activity of Raney nickel varies with its properties. These properties are related to the composition of the bimetallic precursor used to synthesise Raney nickel. The bimetallic precursor consists of a combination of bimetallic phases. Various studies have been done on the well-known bimetallic phases, namely, Ni₂Al₃, NiAl and NiAl₃. However, to get a more comprehensive understanding of the influence of the bimetallic precursor on the properties of Raney nickel, a larger spectrum of bimetallic phases needs to be evaluated. In this study, the Site Occupation Disorder (SOD) program was used to build solid-state structures (bimetallic phases) with various Ni_1-xAl_x bimetallic ratios. These Ni_1-xAl_x bimetallic phases were evaluated, and unique configurations for each Ni_1-xAl_x bimetallic ratio were obtained. The unique configurations were geometrically optimised using the General Utility Lattice Program (GULP) at 0K. These optimised unique configurations were thermodynamically evaluated over a range of 0.1K – 1200K, and the most stable configurations with a probability higher than 10% were identified. This study found that the stable non-homogeneous configurations fall within a range of 20% - 80% Ni content. A weight average combination of these configurations of the bimetallic phases will produce a non-homogeneous precursor with an average Ni content of 20% - 80%, which is in close agreement with experimental results. The approach in this study enables researchers to obtain a larger, repeatable spectrum of bimetallic phases for the investigation of Raney nickel precursors.