BiVO4 photoanodes for water splitting with high injection efficiency, deposited by reactive magnetron co-sputtering

Haibo Gong,Man Nie,Norman Freudenberg,Klaus Ellmer,Roel Van De Krol

doi:10.1063/1.4947121

Haibo Gong, Man Nie + Show 3 more

Open Access

https://doi.org/10.1063/1.4947121

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Abstract

Photoactive bismuth vanadate (BiVO4) thin films were deposited by reactive co-magnetron sputtering from metallic Bi and V targets. The effects of the V-to-Bi ratio, molybdenum doping and post-annealing on the crystallographic and photoelectrochemical (PEC) properties of the BiVO4 films were investigated. Phase-pure monoclinic BiVO4 films, which are more photoactive than the tetragonal BiVO4 phase, were obtained under slightly vanadium-rich conditions. After annealing of the Mo-doped BiVO4 films, the photocurrent increased 2.6 times compared to undoped films. After optimization of the BiVO4 film thickness, the photocurrent densities (without a catalyst or a blocking layer or a hole scavenger) exceeded 1.2 mA/cm2 at a potential of 1.23 VRHE under solar AM1.5 irradiation. The surprisingly high injection efficiency of holes into the electrolyte is attributed to the highly porous film morphology. This co-magnetron sputtering preparation route for photoactive BiVO4 films opens new possibilities for the fabrication of large-scale devices for water splitting.

Highlights

INTRODUCTIONBiVO4 photoelectrodes deposited by spray pyrolysis have reached photocurrents as high as 3.6 mA/cm[2], using blocking layers at the back contact and catalytically active layers.[12] Combining these electrodes with a double-junction thin film amorphous silicon cell resulted in a stand-alone water splitting device with a STH efficiency of 4.9%.12
Which is close to the entry level efficiency for commercialization.[2]
Other synthesis method are based on physical vapor deposition, such as reactive ballistic deposition (RBD),[5] and reactive magnetron sputtering.[14,15]

Summary

INTRODUCTION

BiVO4 photoelectrodes deposited by spray pyrolysis have reached photocurrents as high as 3.6 mA/cm[2], using blocking layers at the back contact and catalytically active layers.[12] Combining these electrodes with a double-junction thin film amorphous silicon cell resulted in a stand-alone water splitting device with a STH efficiency of 4.9%.12. Other synthesis method are based on physical vapor deposition, such as reactive ballistic deposition (RBD),[5] and reactive magnetron sputtering.[14,15] An important advantage of physical vapor deposition techniques over chemical solution methods is the much higher purity that can generally be achieved. Where Jph is the measured photocurrent density in mA/cm[2], Iinc is the incident light intensity in mW/cm[2], and λ is the incident photon wavelength in nm

Structure and composition

Scanning electron microscopy

Optical Properties

Photoelectrochemical properties

CONCLUSIONS