Cadmium Sulphide Sensitized Crystal Facet Tailored Nanostructured Nickel Ferrite @ Hematite Core-Shell Ternary Heterojunction Photoanode for Photoelectrochemical Water Splitting

Abstract

Design of composite semiconductor nanostructures with proper band alignment for efficient charge separation and carrier transport has been at the center of research for photoelectrochemical water splitting. This work demonstrates the deposition of a NiFe₂O₄ @Fe₂O₃ core-shell nanostructured film sensitized with CdS to form a ternary heterojunction for cascade type electron transfer. The hematite nanostructures were grown by hydrothermal approach through dipping into a solution of Nickel Nitrate yielded anchoring of Ni²⁺ ions on the outer surface. The films were then annealed at 650 °C for the diffusion of Ni²⁺ ions into the hematite lattice which forms core-shell NiFe₂O₄ @Fe₂O₃ heterojunction. The films were further sensitized with CdS nanoparticles deposited by a hydrothermal approach to form the final ternary heterojunction photoanode. Several different nanostructures were grown and the effect of crystal facet tailoring was observed on Ni loading and photoelectrochemical performance. The photoelectrochemical measurements were carried out using a potentiostat under 100 mW/cm² light source (150W Xenon Lamp) with Pt counter electrode and 0.5 M Na₂S and 0.5 M Na₂SO₃ electrolyte. A current density of 3.47 mA/cm2 was observed at 1.23 V (vs Ag/AgCl). An Applied Bias to Photocurrent Efficiency (ABPE) of 1.8 % photoconversion efficiency was observed using the fabricated electrodes at 0.288V (vs Ag/AgCl).