Enhanced efficiency of hematite photoanode for water splitting with the doping of Ge

Ge doped α-Fe₂O₃ nanowires are synthesized through a hydrothermal procedure with GeO₂ as a precursor and investigated as photoanodes for water splitting. The content of Ge in the photoanode rises with the increase of the amount of GeO₂ in the precursor solution. A proper amount of Ge facilities the preferred oriented growth of the (110) plane of α-Fe₂O₃, while excessive Ge hinders the growth of α-Fe₂O₃ crystals. The doping of Ge increases the absorption efficiency and decreases the recombining rate of the photogenerated electrons and holes. Ge also improves the density and transfer rate of the charge carriers in the photoanode. Ge doped α-Fe₂O₃ photoanode exhibits a highest photocurrent density of 0.92 mA cm⁻² at 1.23 V vs. reversible hydrogen electrode under AM 1.5 G simulated sunlight, which is nearly twice of that obtained by pure α-Fe₂O₃ under the same condition.