Fabrication of In2O3/ZnO hetero-epitaxial-junctions with enhanced PEC performances

Abstract

In2O3/ZnO hetero-epitaxial-junction photoanodes were successfully synthesized and applied for the photoelectrochemical splitting of water. With the assistance of In2O3, the light absorption of In2O3/ZnO heterojunctions can effectively expand to visible light absorption region. Due to the epitaxial relationship between (10-10) ZnO and {-211} In2O3 planes, the staggered band alignments between In2O3 and ZnO can produce a built in electric field at the heterojunction interface with a high quality, which can promote the charge separation and lower the charge recombination under light irradiation. Moreover, low index crystal facets, such as {001} and {111} facets, with lower surface energies can be formed spontaneously in In2O3 nanoparticles due to the surface energy conservation. And the presence of In2O3 {001} facets can effectively lower the onset potential and facilitate the water oxidation. With the synergistic effects mentioned above, In2O3/ZnO-6 exhibit highest photocurrent density of 2.2 mA cm−2 at 0.6 V vs Ag/AgCl and IPCE value of 88.62% at 0.25 V vs Ag/AgCl (370 nm), which is 2.82 and 4.4 times as high as that of ZnO NRs and In2O3 photoanodes, respectively.