An optimized Fe3O4/Fe2O3 PN junction photoelectrode with multiscale structure and broad spectrum absorption

A Fe3O4/Fe2O3 photoelectrode exhibiting excellent broadband and light-trapping characteristics has been pre-pared. It is found to be of unique multi-scale structure that is composed of pyramids from 5 to 10 mu m in width grown on nanorod arrays from 400 to 500 mu m in diameter. This multi-scale structure displays an extraordinary surface catalytic-activity and photothermal effect, which result in strong absorption in UV-Vis-NIR region and significantly improved PEC performance. Besides, type II p-n Fe2O3/Fe3O4 heterojunction with suitable energy position and its built-in electric field favor separation and transfer of photogenerated carriers. The optimized Fe2O3/Fe3O4 photoanode therefore exhibits a much larger photocurrent density-0.68 mA/cm2 at 1.23 V vs. RHE under simulated sunlight illumination compared to 0.08 mA/cm2 of the pure Fe2O3 photoelectrode. This unique design for multi-scale structure may provide a route to develop high-efficient photoelectrode with full -spectrum response.