The study of photoelectrochemical properties of LaMnO₃, LaFeO₃, LaCrO₃, and LaNiO₃ photoelectrodes for hydrogen production

The LaMnO₃, LaFeO₃, LaCrO₃, and LaNiO₃ films were deposited on aluminum plate substrates by sol–gel method. Physical characterization and photoresponse studies were carried out to investigate the possibility of applying these film electrodes in solar photoelectrochemical systems. X-ray diffractions analysis revealed the crystal structures of the films with LaNiO₃ having the smallest grain size of 40.87 nm, corresponding well to the results obtained from field emission scanning electron microscopy/energy-dispersive analysis. Pore size distribution analysis showed that the films exhibited highly porous and hierarchical structures. The band gaps and carrier densities determined using photoluminescence spectrum and Mott–Schottky analysis were in the range of 2.28–2.67 eV, and 3.95 × 10¹⁵–7.65 × 10¹⁷ cm⁻³, respectively. The flat-band potentials lay in between −0.217 and −0.459 V versus normal hydrogen electrode. Based on these, the conduction and valance bands of the films were found to be in the range of −0.386 to −0.685, and +1.718 to +2.284 V versus normal hydrogen electrode, respectively. LaNiO₃ film yielded the maximum photocurrent density of 0.54 mA/cm² in 0.1 M KOH with external potential kept at 0.5 V and illumination at 100 mW/cm². This paper demonstrated the effectiveness of the sol–gel approach for producing thin-film semiconductor with great potential in hydrogen production due to its high stability and photoelectrochemical efficiency in the visible light region.