Energy band gap tuning of LaNiO3 by Gd, Fe and Co ions doping to enhance solar light absorption for efficient photocatalytic degradation of RhB dye: A mechanistic approach

A series of Gd, Co and Fe substituted LaNiO3 perovskite oxides were synthesized via microemulsion approach. The influence of dopants was investigated on the basis of ferroelectric, dielectric and photocatalytic properties. X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV–Visible spectroscopic techniques were employed for the characterization of prepared samples. XRD analysis confirmed the distorted rhombohedral phase with space group R3¯c and the grain size was in 65–48 nm range. The ferroelectric and dielectric parameters including AC conductivity were increased except AC resistivity with dopant contents. The band gap energy was reduced significantly in doped samples from 3.01 to 2.43 eV. A decrease in PL (photoluminescence) intensity was also observed in doped samples. The PCA (photocatalytic activity) of pure and substituted LaNiO3 was studied by photodegradation of RhB (rhodamine B) dye under visible light exposure. The LNGCF5 (x = y = 0.25) composition exhibited superior PCA of 97% within 120 min irradiation time in comparison to pure LaNiO3. The rate constants for LaNiO3 and LNGCF5 were 0.006 min−1 and 0.0096 min−1, respectively. Furthermore, effect of catalyst load and pH on kinetics of PCA was also studied, which affected the RhB dye degradation significantly. The enhanced dielectric constant and AC conductivity of LNGCF (1–5) introduce these materials as potential candidates for dielectric resonator and memories devices. The increased ferroelectric polarization along with low band gap energy improved their ferroelectric photovoltaic response, which makes their feasibility in photovoltaic devices. Superior PCA of LNGCF5 under visible illumination in comparison to pure LaNiO3 introduces this material as promising photocatalyst for the removal of hazardous and toxic dyes in effluents under solar light irradiation.