Efficient Nanoporous Hematite Photoanodes Prepared by Electron Beam Evaporation and Au Modification

Abstract

AbstractThe water oxidation efficiency of hematite photoanodes is mainly limited by low visible light absorption and short hole diffusion length. Herein, we report on production of nanoporous columnar hematite films modified with Au nanoparticles (NPs) to overcome these drawbacks. The hematite films are prepared by electron beam evaporation. By optimization of deposition conditions including film thickness, annealing and performing the evaporation under oblique angle, an efficient photoelectrochemical (PEC) performance is achieved from the pristine hematite photoanode. Then, Au NPs are infiltrated into the hematite films by a spin coating process. The water oxidation of hematite films is further enhanced after Au modification. The most efficient electrode generates a photocurrent density of 2.7 mA cm−2 at 1.5 V (RHE), showing about two‐fold improvement relative to that of bare hematite. Optical and electrochemical analyses suggest that the improvement after Au modification can be attributed to plasmonic and facilitating surface charge transfer. The contributions of different plasmonic mechanisms to the photocurrent enhancement are qualitatively discussed based on optical characterization and electromagnetic simulations. Electrochemical impedance spectroscopy is carried out to confirm the improvement of surface charge transport by the Au NPs. Our findings show that Au modification is a favorable strategy to improve the PEC performance of hematite photoanodes prepared by PVD methods.