Deposition of Size-Selected Gold Nanoclusters onto Strontium Titanate Crystals for Water Splitting under Visible Light

Using a modulated pulse power magnetron sputtering (MPP-MSP) coupled with a quadrupole mass spectrometer (Q-MS), intensive size-selected gold nanoclusters (Aun) ranging from n = 5 to 40 in size are synthesized and soft landed onto a strontium titanate (STO) crystal surface as a co-catalyst for photocatalytic water splitting. The photocatalytic reactivity of the Aun/STO is investigated by measuring the photocurrent density of the sample under visible light radiation. It is found that the Aun co-catalysts enable the visible light response of the Aun/STO photocatalyst. The photocurrent density is sensitively dependent on the size of the Aun on the STO, and Au16 exhibits its maximum photocurrent under visible light. The underlying physics of the size-specific photocurrent are explained in terms of the size-dependent electron affinity of Aun.