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We report the structural, mechanical, electronic, optical, thermoelectric properties and spectroscopic limited maximum efficiency (SLME) of oxide double perovskite structure Ba2SbNbO6 and Ba2SbTaO6 compounds. All the investigations were performed through the first-principles density functional theory (DFT). The results obtained for the elastic constants affirms the mechanical stability of the studied double perovskite compounds. The calculated data of bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba2SbTaO6 are found to be greater than those of Ba2SbNbO6. The obtained ratio of Bulk to shear modulus (B/G) shows that Ba2SbNbO6 and Ba2SbTaO6 are ductile in nature and are suitable for the device fabrications. The electronic properties of studied compounds are explained in terms of their energy bands, total and partial density of states. The computed electronic band structure reveals the direct band gap semiconducting nature of both compounds. The energy dependent optical properties such as, dielectric tensor, optical conductivity, absorption, reflectivity, refraction and energy loss for both the studied compounds are investigated and are explained in order to highlight the potential of studied compounds for the photovoltaic applications. In addition to electronic and optical properties, we have also studied the electron relaxation time-dependent thermoelectric properties, such as Seebeck coefficient, electronic thermal conductivity, electrical conductivity, thermoelectric power factor, and the thermoelectric figure of merit as a function of chemical potential at various temperatures for p-type and n-type charge carriers. The high absorption spectra and good thermoelectric figure of merit reveal that both the studied compounds, Ba2SbXO6 (X = Nb, Ta) are promising materials for photovoltaic and thermoelectric applications. The calculated SLME of 26.8% reveals that Ba2SbNbO6 is an appealing candidate for single-junction solar cells.

The oxygen evolution reaction (OER), owing to its sluggish nature, demands efficient and stable catalysts with low production cost, during the electrocatalytic water splitting. In this respect, a series of bimetallic ZnO-Ni(OH)2 composite materials were prepared as electrode materials for OER. The synthetic procedure followed the polyvinylpyrrolidone (PVP) and dopamine (DA) assisted hydrothermal process. The growth modification ability of PVP and adhesive property of polydopamine (from DA) were utilized to attain the 3D interconnected structures. The precursor concentrations were varied to obtain most efficient catalyst, ZNDP-1. In alkaline medium, ZNDP-1 showed a low over potential of 170 mV (@10 mAcm−2 current density) and a Tafel slope of 61 mV dec−1 with significant stability. The surface defects, porosity and synergism within metal centers might cause efficient electrocatalytic activity. Furthermore, DFT studies were performed to understand the mechanistic pathway.