Photocatalysis and Photosensitization Using Atomically Precise Metal Nanoclusters for Solar Energy Harvesting and Conversion

Metal nanoclusters (NCs) with atomic precision are a unique family of metal nanomaterials that are readily crystalized into single crystals, representing ideal models to unravel structure-property relationship at atomic level. By tuning the number of metal atoms in the core, the composition and the protecting ligand of metal NCs, their physicochemical properties can be precisely controlled. The strong, broad light absorption ability and the long-lived excited states make metal NCs promising candidates as photosensitizer, and might replace traditional dyes. Their discrete energy levels allow them to prevent charge recombination at the semiconductor by efficiently separate the photoinduced charge carriers. Moreover, these metal NCs themselves can act as active catalysts. In the first part of the talk, we demonstrate the differences of working principle between metal NCs and their particle counterparts in photocatalytic system. The metal NC modified TiO₂ catalyst is found to exhibit a fiver times higher performance than TiO₂ modified with metal nanoparticles in the photocatalytic H₂ production reaction.^[1]In the second part, we present the strategy to tune the charge transfer pathways of metal NCs sensitized semiconductors in photoelectrochemical system. While metal NCs serve as catalyst for oxidation reactions when loaded on n-type semiconductor, they serve as catalyst for reduction reactions when loaded on p-type semiconductor.^[2]In the last part, we will use Au₂₅ NC as an example to demonstrate how the protecting ligand and the composition of the metal NC influence the overall performance of a NC/semiconductor system in photocatalytic H₂ production.^[3]<br/><br/>[1] Wang, Y.; Liu, X.-H.; Wang, Q.; Quick, M.; Kovalenko, A. S.; Chen, Q.-Y.; Koch, N.; Pinna, N. <i>Angew. </i><i>Chem. Int. Ed.</i> <b>2020</b>, <i>59</i>, 7748-7754.<br/>[2] Wang, Y.; Liu, X.-H.; Wang, R.; Cula, B.; Chen, Z.-N.; Chen, Q.-Y.; Koch, N.; Pinna, N. <i>J. Am. </i><i>Chem. Soc.</i> <b>2021</b>, <i>143</i>, 9595-9600.<br/>[3] Liu, Y.; Wierzbicka, E.; Springer A.; Pinna N.; Wang, Y. <i>J. Phys. </i><i>Chem. C</i> <b>2022</b>, <i>126</i>, 1778-1784.