Geometric Optimization of Bismuth Vanadate Core–Shell Nanowire Photoanodes using Atomic Layer Deposition
2021
Bielinski, Ashley R. | Gayle, Andrew J. | Lee, Sudarat | Dasgupta, Neil P.
In this study, systematic geometric tuning of core–shell nanowire (NW) architectures is used to decouple the contributions from light absorption, charge separation, and charge transfer kinetics in photoelectrochemical water oxidation. Core–shell–shell NW arrays were fabricated using a combination of hydrothermal synthesis of ZnO and atomic layer deposition (ALD) of SnO₂ and BiVO₄. The length and spacing of the NW scaffold, as well as the BiVO₄ film thickness, were systematically tuned to optimize the photoelectrochemical performance. A photocurrent of 4.4 mA/cm² was measured at 1.23 V vs RHE for sulfite oxidation and 4.0 mA/cm² at 1.80 V vs RHE for water oxidation without a cocatalyst, which are the highest values reported to date for an ALD-deposited photoanode. Electromagnetic simulations demonstrate that spatial heterogeneity in light absorption along the core–shell NW length has a critical role in determining internal quantum efficiency. The mechanistic understandings in this study highlight the benefits of systematically optimizing electrode geometry at the nanoscale when designing photoelectrodes.
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