Construct Fe2+ species and Au particles for significantly enhanced photoelectrochemical performance of α-Fe2O3 by ion implantation

Abstract

Photoelectrochemical (PEC) water splitting is a promising approach to producing H2 and O2. Hematite (α-Fe2O3) is considered one of the most promising photoelectrodes for PEC water splitting, due to its good photochemical stability, non-toxicity, abundance in earth, and suitable bandgap (Eg∼2.1 eV). However, the PEC water splitting efficiency of hematite is severely hampered by its short hole diffusion length (2–4 nm), poor conductivity, and ultrafast recombination of photogenerated carriers (about 10 ps). Here, we show a novel and effective method for significantly improving the PEC water splitting performance of hematite by Au ion implantation and the following high-temperature annealing process. Based on a series of characterizations and analyses, we have found Fe2+ species and tightly attached Au particles were produced at Au-implanted hematite. As a result, the charge separation and charge injection efficiency of Au-implanted Fe2O3 are markedly increased. The photocurrent density of optimized Au-implanted Fe2O3 could reach 1.16 mA cm−2 at 1.5 V vs. RHE which was nearly 300 times higher than that of the pristine Fe2O3 (4 μA cm−2). Furthermore, the Au-implanted Fe2O3 photoelectrode exhibited great stability for the 8-hour PEC water splitting test without photocurrent decay.