Gradient doping of phosphorus in Fe(2)O(3) nanoarray photoanodes for enhanced charge separation

Hematite (α-Fe(2)O(3)) is a promising candidate for solar-to-hydrogen energy conversion. However, the low carrier mobility and extremely high charge recombination rate limit the practical application of hematite in solar water splitting. This paper describes the fabrication of a Fe(2)O(3) photoanode with gradient incorporation of phosphorus (P) employing a facile dipping and annealing method to improve the charge separation for enhanced photoelectrochemical water oxidation. This gradient P incorporation increases the width of band bending over a large region in Fe(2)O(3), which is crucial for promoting the charge separation efficiency in the bulk. Although both gradient and homogeneous P-incorporated Fe(2)O(3) samples exhibit similar electrical conductivity, the Fe(2)O(3) electrode with a gradient P concentration presents an additional charge separation effect. A photocurrent of ∼1.48 mA cm(–2) is obtained at 1.23 V vs. reversible hydrogen electrode (vs. RHE) under air mass 1.5G illumination. Additionally, the H(2)O oxidation kinetics of Fe(2)O(3) with gradient P incorporation was further improved upon loading cobalt phosphate as cocatalyst, reaching a photocurrent of ∼2.0 mA cm(–2) at 1.23 V vs. RHE.