Improvization of synthetic strategies for designing novel nanostructures with desirable tailored morphology for efficient solar energy utilization has been at the focus of research on photoelectrochemical water splitting. This work presents a novel fabrication technique comprised of photocathodes comprised of highly porous copper ferrite nanoflake arrays by low-temperature surfactant-assisted solvothermal phase change induced temperature-controlled etching process. Solvothermally predeposited hematite on FTO glass was treated by a second solvothermal step, whereby surfactant-capped Cu2+ ions were forcibly impregnated into the hematite lattice at varying temperatures, resulting in phase change along with a drastic change in nanostructure morphology and crystal phase without the formation of any copper oxide surface impurities causing a temperature-dependent control over the degree of spinel inversion (δ), the underlying electronic properties of which were analyzed using DFT calculations. Analysis of photoelectrochemical (PEC) performance of the fabricated photocathodes was performed under A.M 1.5 G simulated solar illumination under a linear voltage sweep using a potentiostat with the three-electrode setup using 1 M H2SO4 aqueous solution as an electrolyte. The photocathode with δ = 0.77 exhibited the highest photocurrent density of −0.139 mA/cm2 at 0 V (vs RHE) and −2.57 mA/cm2 at −1 V (vs RHE). It also exhibited the highest IPCE % of 18.7%, which was higher than that of the photocathode with δ = 0.71, because of the depreciatory effect of high temperature on morphology, thereby emphasizing the precise synergistic influence of phase and morphology control simultaneously upon PEC performance. This work should inspire further research in developing unique wet chemical synthesis strategies for designing porous and highly ordered impurity-free nanostructures with temperature-dependent phase control for photoelectrode applications.

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Development of efficient semiconductor heterostructures with adequate band alignment for enhanced charge separation and increased light absorbance has been at the forefront of research on photoelectrodes. In this work we demonstrate the fabrication of CdS sensitized CoTiO3 @ TiO2 photoanodes for photoelectrochemical water splitting. TiO2 nanorods were synthesized by a hydrothermal method followed by surfactant assisted solvothermal impregnation of Co2+ ions into the TiO2 lattice resulting in development of a core-shell CoTiO3 @ TiO2 p-n junction heterostructure. The photoanodes were further sensitized by CdS nanoparticles by a facile SILAR method not only to increase light absorbance in the visible region but also to form a ternary heterojunction photoanode with cascade type electron transfer. The fabricated photoanodes showed an ABPE % of 0.43% at 0.6 V vs Ag/AgCl reference electrode using 0.5 M Na2S and 0.5M Na2SO3 electrolyte under A.M 1.5 G simulated solar illumination. Optical properties were analyzed using UV-Vis Absorbance and Photoluminescence Spectroscopy. Transient photocurrent, EIS and Mott-Schottky analysis were carried out to analyze charge transport processes occuring at the semiconductor / electrolyte interface. Structure and morphological analysis was carried out using XRD and FESEM. Band structure and DOS was analyzed using DFT calculations.This work hopes to inspire new research in development of ternary heterojunctions for photoelectrochemical water splitting.