The Ni1-xZnxAl2O4 solid solution (0 ≤ x ≤ 1) has been prepared by sol gel route. The crystallites sizes (36–47 nm)} were determined from the broadening of X-ray diffraction peaks. TEM images give homogeneous distribution of crystallites with a size between 50 and 100 nm while the BET analysis gave low specific surface areas (1.98–6.03 m2/g). The UV-Visible spectrophotometry shows direct transitions (2.50–3.22 eV) due the Ligand Charge Transfer (LCT): O2−: 2p → Ni2+: 3d. Field-dependent magnetization was measured at 300 K in the region (±25 kOe) and Ni1-xZnxAl2O4 exhibits a magnetism with a saturation between 0.17 and 0.71 emu/g while the coercivity does not change significantly and fluctuates in the range (30–35 Oe). The Intensity-Current (J-E) plots in Na2SO4 solution (0.1 M) are similar to chemical diodes with small current densities (~ 0.5 mA cm−2) and a low hysteresis The hole concentrations (NA × 1017: 8.4–10) are computed from the capacitance plots in Na2SO4 solution, which also give flat band potential (Efb: − 0.05, + 0.20 V), due to the lower electronegativity of Zn2+. The latter does not vary significantly due to closeness of electronegativity of Ni and Zn and indicates that both the valence and conduction bands derive from 3d orbital (~ − 5 eVvaccum). The oxides are promising for H2 production under visible light.
