Synthesis and Optical-Electronic Characterization of Nickel Pyro-Vanadate A2NiV2O7 (A = Na, Ag) Semiconductors: Experimental, DFT, and Hybrid-DFT Approaches

Semiconductors, with their exceptional properties, have diverse applications across fields such as photovoltaics, sensing, and catalysis. In the present study, nickel pyro-vanadate compounds of high purity and homogeneity, with the chemical formula A 2 NiV 2 O 7 (where A = Na, Ag), were synthesized under precisely controlled stoichiometric conditions. The primary focus is to investigate the optical and electronic properties of these compounds using a combination of experimental techniques and theoretical modeling. Initially, insights into the chemical structure and morphology of the synthesized semiconductor were obtained through powder x-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). A 2 NiV 2 O 7 were found to be homogeneous, crystalline in nature, and isotypic with Κ 2 CoV 2 O 7 , exhibiting alternating layers of NiV 2 O 7 and Ag/Na. Moreover, absorption spectra obtained from UV–Vis diffuse reflectance spectroscopy (DRS) showed direct optical bandgaps of 1.83 eV for Na 2 NiV 2 O 7 and 1.92 eV for Ag 2 NiV 2 O 7 , affirming their semiconductor properties. Further characterization was performed using density functional theory (DFT) and hybrid-DFT methods. These advanced techniques provide detailed understanding of the electronic structure and properties across different sodium–silver ratios. The computed electronic structures demonstrate the separation of the conduction band (CB) and valence band (VB) around the Fermi level, with bandgaps of 0.44 eV and 1.76 eV for Na 2 NiV 2 O 7 , and 0.56 eV and 1.60 eV for Ag 2 NiV 2 O 7 , as determined using the Perdew–Burke–Ernzerhof (PBE) and DFT+U methods, respectively. This comprehensive investigation offers valuable insights into the optical and electronic dynamics of nickel pyro-vanadate compounds, establishing a foundation for their potential applications in various fields, including optoelectronics, photocatalysis, and energy storage. Graphical abstract