Schematic illustration of the fabrication procedures for Ni(OH)2/ZnO core–shell NR arrays on FTO substrates.
Schematic illustration of the fabrication procedures for Ni(OH)2/ZnO core–shell NR arrays on FTO substrates.

Designing high-performance photoanodes is essential for efficient solar energy conversion in photoelectrochemical (PEC) water splitting. In this paper, we report an effective approach to improve the PEC performance of ZnO nanorod (NR)-based photoanodes by introducing low-crystalline Ni(OH)2 electrocatalyst nanosheets onto the ZnO surfaces. ZnO NR arrays and Ni(OH)2 nanosheets were grown sequentially by electrochemical deposition, forming a core–shell structure. The ZnO NR cores acted as photon absorber as well as rapid charge transporter; whilst the wrinkled Ni(OH)2 nanosheets largely increased the surface area and facilitated the PEC process by lowering the energy barrier of water oxidation and suppressing electron–hole recombination. As a result, more than one order of magnitude enhancement of PEC efficiency was obtained from the Ni(OH)2/ZnO core–shell NR photoanode compared to bare ZnO NRs. The thickness effect of Ni(OH)2 overcoating was also investigated. It was observed that although the electrocatalytic effect increased monotonically with the amount of Ni(OH)2 coating, too much Ni(OH)2 coverage could reduce the photocatalytic effect by limiting the light absorption. This research demonstrates that introducing appropriate amount of Ni(OH)2 electrocatalysts can effectively facilitate the PEC performance of ZnO photoanodes. It suggests a promising route toward high-performance photoanode design for efficient solar energy conversion.

This paper was originally published in Nano Energy 6, (2014), 10-18.

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