Photoelectrochemistry of Co-Modified Hematite Surfaces for Solar Water Splitting

Abstract

Co-modified hematite (Co-modified α-Fe2O3) thin films were prepared via a combination of sputtering and wet impregnation as well as deposition annealing (DA), and analyzed as photoanodes for water splitting. By varying the number of DA cycles using a Co metal-containing solution, Fe2O3 thin films with a range of compositions of Co could be prepared. The films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–vis absorption spectroscopy. The most notable observed effect of film composition on photoelectrochemical (PEC) performance was the dark current onset potential, which was observed to shift up to 0.13 V in 1.0 M KOH solution. Possible effects of Co-modification are discussed, including lattice distortion, surface state passivation, and carrier density/conductivity. The PEC results for these Co-modified Fe2O3 thin films illustrate the complex relationship between the catalytic and photocatalytic nature of cobalt.