Design Principles and Interfacial Engineering in an In Situ Grown Nickel Oxy-Nitride (NixOyNz) System Manifesting Synergistic Properties for Photocatalysis

A robust in situ nickel oxynitride (NixOyNz) system is synthesized by solid-state annealing of nickel nitride at a relatively low temperature of 400 °C, as confirmed by XRD and Rietveld refinement analysis. XPS investigations revealed that the oxynitride phase is evolved and stabilized by a network involving N3–, Ni3+/2+/0, and O2– in the system. The enhanced properties of the developed oxynitrides emerged via the synergistic interactions between the nickel nitride–nickel oxide–metallic nickel components, owing to their quantum-cascading electronic band alignments in the system. Consequently, the developed NixOyNz system exhibited impressive photocatalytic efficiencies, including ∼98/88% degradation of MB/RhB dyes in 150 min and the production of H2 and NH3 at rates of 339.7 and 239.8 μmol g–1 h–1, respectively, under visible light, surpassing the performance of the bare oxide and nitride systems. The improved magnetic properties and photostabilities of the synthesized NixOyNz system allowed for easy recovery and reusability, as confirmed in its postcharacterization studies. The findings of the study revealed that the formation of a NixOyNz system with tunable phases can be feasible from a pre-engineered Ni3N system, and the resulting NixOyNz can be a robust photocatalyst for energy-efficient multifaceted photocatalytic applications, as demonstrated in this study.