Controlled Aqueous Growth of Hematite Nanoplate Arrays Directly on Transparent Conductive Substrates and Their Photoelectrochemical Properties

Two-dimensional (2D) hematite nanoplate arrays were synthesized directly on fluorine-doped tin oxide (FTO)-coated glass by using a facile and novel hydrothermal method. High-temperature annealing retained the morphology of the nanoplate arrays while simultaneously introducing porosity. The thickness and length of the nanoplates could be tailored by adjusting the precursor composition. Photoelectrochemical (PEC) measurements showed that the photocurrent generated with bare hematite nanoplate photoelectrode under backside illumination was about four times of that under frontside illumination in the entire bias range used, which suggested that slow electron transport was a limiting factor for its PEC performance. Upon Sn doping and Co-Pi co-catalyst addition, the photocurrent increased significantly owing to the enhancement of electron conductivity and oxidation kinetics. Electrochemical impedance spectroscopy (EIS) measurements were conducted to understand the surface properties of the nanoplate arrays. Since this strategy is simple, cost-effective, and highly reproducible, it provides exciting opportunities for the large-scale growth of porous 2D metal oxide photoelectrodes for a variety of photoelectrochemical and photocatalytic applications.