From Solid Solution to Intermetallic Compounds: Oxygen Evolution Reaction Activity Trends among Nb–Ni Phases

The electrochemical behavior of Nb–Ni binary phases in terms of electrocatalytic activity and stability under oxygen evolution reaction (OER) conditions was investigated. The outcomes of electrochemical studies in an alkaline electrolyte, supported by extensive characterization of electrode materials before and after electrochemical experiments, were provided. OER activities using the intermetallic compounds Nb7Ni6 and NbNi3 as electrocatalyst precursors were compared with those obtained with the solid solution of NbxNi1-x (x = 0.09) and a reference Ni foil under the same conditions. While Nb7Ni6 deactivates gradually during benchmarking stability test (chronopotentiometry at current density of 10 mA cm–2 for 2 h), NbNi3 possesses remarkable OER activity and keeps it stable not only under mild conditions of benchmarking experiment but also during long-term operation at elevated current densities (50, 100, and 200 mA cm–2). To understand the difference in chemical behavior and the OER performance of Nb–Ni compounds, extensive characterization was supported by carrying out quantum chemical calculations, shedding light on the charge distribution and chemical bonding in the investigated compounds.