Highly self-diffused Sn doping in -Fe2O3 nanorod photoanodes initiated from -FeOOH nanorod/FTO by hydrogen treatment for solar water oxidation

摘要

In this study, we present an advanced strategy of low-temperature hydrogen annealing combined with high- temperature quenching in air for activating -Fe2O3 nanorod photoanodes to boost the photoelectrochemical performance. We report that various low-temperature annealing conditions (340, 360, 380, and 400 degrees C) under hydrogen gas flow convert -FeOOH into magnetite (Fe3O4) as well as introduce Sn4+ diffusion from FTO substrates to its surface. Furthermore, high-temperature quenching (800 degrees C) resulted in the phase change of magnetite (Fe3O4) into hematite (-Fe2O3) and self Sn4+ doping into the hematite lattice. Thus, the hydrogen-assisted thermally activated hematite photoanode achieved a photocurrent density of 1.35 mA cm(-2) at 1.23 V vs. RHE and 1.91 mA cm(-2) at 1.4 V vs. RHE, which is 70 and 80 higher than that of directly quenched hematite at 800 degrees C. These combined two step strategies provide new insight into high Sn-self doping for -Fe2O3 photoanodes and allow for further development of more efficient solar water oxidation systems.