Ni(OH)2 nanocrystals have emerged as an important class of functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen (HER) and oxygen evolution reactions (OER). However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions, crucial for solar fuel conversion, remain unexplored. In this paper, we investigate the CS and charge recombination (CR) dynamics of a newly designed hybrid catalyst by integrating a molecular photosensitizer with Ni/Ni(OH)2 core/shell nanoparticles (NPs). We show that by using a Ru complex as a model photosensitizer, ultrafast CS occurs through electron transfer from the excited Ru complex to Ni/Ni(OH)2 NPs, which is followed by slow CR. In addition to the spectral features due to CS and CR observed by optical transient absorption spectroscopy (OTA), the direct evidence for CS and CR, i.e. the formation and recovery of the reduced Ni site in the hybrid, is captured by X-ray transient absorption spectroscopy (XTA). These results not only suggest the possibility of developing Ni(OH)2 as a solar fuel catalyst, but also represent the direct observation of efficient CS in a photosensitizer/semiconductor solar fuel catalyst hybrid using XTA.

Photoinduced electron injection from ruthenium complex to Ni/Ni(OH)2 core/shell nanoparticles

251st National Meeting (2016)

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