CNT-ZnO Core-Shell Photoanodes for Photoelectrochemical Water Splitting

Abstract

Solar-driven water splitting is a promising route toward clean H2 energy and the photoelectrochemical approach attracts a strong interest. The oxygen evolution reaction is widely accepted as the performance limiting stage in this technology, which emphasizes the need of innovative anode materials. Metal oxide semiconductors are relevant in this respect owing to their cost-effectiveness and broad availability. The combination of chemical vapor deposition and atomic layer deposition was implemented in this study for the synthesis of randomly oriented CNT-ZnO core-shell nanostructures forming an adhering porous coating. Relative to a directly coated ZnO on Si, the porous structure enables a high interface area with the electrolyte and a resulting 458% increase of the photocurrent density under simulated solar light irradiation. The photoelectrochemical characterization correlates this performance to the effective electrons withdrawing along the carbon nanotubes (CNTs), and the resulting decrease of the onset potential. In terms of durability, the CNT-ZnO core–shell structure features an enhanced photo-corrosion stability for 8 h under illumination and with a voltage bias.