(Invited) Co-Doping for Solving a Short-Hole Diffusion Length Issue of Hematite in Water Splitting

Abstract

Titanium and boron hetero-doped hematite photoanodes with an n-n+ homo-junction showed significantly increased photoelectrochemical (PEC) water splitting activity. The Ti and B co-doping in hematite not only suppresses the number of Ti4+and Sn4+ions that cause electron hole pair (EHP) recombination at the hematite surface but also generates an internal electric field for easy hole extraction. The Ti:B-Fe2O3 with a 890 nm height and 70 nm diameter converted the incident photons to EHPs with much reduced recombination and exhibited an excellent photocurrent density of 1.92 mA/cm2at 1.23 VRHEand 2.83 mA/cm2at 1.50 VRHE.Our co-doping strategy provides a straightforward way of addressing the chronic short-hole diffusion length issue that causes a high electron hole recombination rate and thus the critical length limitation of an ideal hematite photoanode, to potentially improve the performance of PEC devices.