Core-shell-shell nanoparticles for the plasmonic enhancement of hematite for photoelectrochemical water splitting
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Photoelectrochemical (PEC) water splitting is a promising method to harness and store the sun’s energy in the form of H2 gas. Hematite (α-Fe2O3) is a potentially outstanding photoanode material for such PEC cells, with excellent stability, earth-abundant materials, and high theoretical solar-to-hydrogen efficiency. However, more optimization is needed in practice to make hematite a viable candidate for future large-scale hydrogen production. This thesis focuses on the plasmonic enhancement of hematite nanostructured photoanodes through the novel use of Au@SiO2@Au core-shell-shell (CSS) nanoparticles. Two different CSS/hematite architectures have been studied – a top-deposited configuration with the CSS NPs on the surface of the hematite, and an embedded configuration with the hematite nanocorals grown over the CSS NPs. The average photocurrent density, as a measure of the PEC activity, was found to improve by a factor of 27% from bare hematite to the top-deposited CSS NP/hematite configuration, and improved by a factor of 90% for the embedded CSS NP/hematite configuration. In particular, the best embedded sample showed an improvement in photocurrent density from 0.82 mA/cm2 with bare hematite to 3.0 mA/cm2 with embedded CSS NPs. This is over a 200% improvement, or a 2.18 mA/cm2 raw photocurrent improvement, representing, to the best of my knowledge, the highest plasmonic-based improvement of any reported hematite photoelectrocatalytic system. Comparison with Au NPs shows that the CSS NP outperformed Au NPs by 2 times in the top-deposited configuration and up to 4 times in the embedded configuration. These results highlight CSS NPs as a new and improved plasmonic system for enhancing the photocatalytic performance of hematite, and could play a key role in pushing hematite to solar-to-hydrogen efficiencies suitable for large-scale H2 production.