Understanding the Photoelectrochemical Behavior of Metal Nanoclusters: A Perspective

Abstract

Since the invention of metal nanocluster (NC)-based photoelectrochemical (PEC) devices, limited progress has been made in this area due to various intricacies associated with this new class of photoactive nanomaterials. Recent research has shown that NC−TiO 2 photoelectrodes possess charge separation and transfer complexities that are not seen in dye− TiO 2 or quantum dot−TiO 2 photoelectrodes. Even the degradation mechanism of NC-based photoelectrodes has a multitude of complexities, such that the degradation of NCs can have a silver lining of introducing plasmons to enhance charge separation in NC−TiO 2 photoelectrodes. Therefore, NC-based photoelectrodes require a comprehensive overview from a photoelectrochemistry perspective to better understand these systems. In this Perspective, we provide a review of recent progress in understanding the degradation and charge transfer mechanisms of NC−TiO 2 photoelectrodes. We also provide an overview of the various methodologies to control the properties of NCs for PEC applications and how these variables have been utilized to improve NC-based PEC device performance. Finally, we discuss the future of NC-based PEC devices and highlight the immense research opportunities present in this field.

Dual Functionality of Surface States in Dictating Photocurrent Generation of Au Nanocluster-Sensitized TiO2 Electrodes

“…We selected GSH-protected Au 18 (SG) 14 NCs as photosensitizers due to their exceptional light absorption, suitable energy positions, and robust chemical stability. 43 The UV−vis absorption spectra of the synthesized Au 18 (SG) 14 NCs closely matched those reported earlier (Figure S2), 42 confirming the successful synthesis of the desired NCs. These NCs were electrostatically adhered to the TiO 2 surface via carboxylic groups in GSH for varying sensitization times (1, 6, 12, 24, and 48 h).…”

“…Synthesis of Au 18 (SG) 14 NCs. Au 18 (SG) 14 NCs stabilized with GSH were synthesized using a CO reduction method. 42 In the initial step, 12.5 mL of a 20 mM gold solution was added to a roundbottom flask containing 227.5 mL of deionized water.…”

Singlet Oxygen Generation Using Thiolated Gold Nanoclusters under Photo- and Ultrasonic Excitation: Size and Ligand Effect

“…53 Two possible oxidative species cause the degradation of Au 25 NCs under photo-and ultrasonic excitation: (1) 1 O 2 -induced oxidation of Au NCs 19 and (2) accumulation of positive charges (holes) in the Au NCs resulting in oxidation. 54 To clarify the oxidative species causing Au 25 NC degradation, we examined the degradation behavior of Au 25 (SG) 18 under visible light in the presence of 1 O 2 scavenger (histidine) or hole scavenger (triethanolamine), as depicted in Figure S6. Au 25 (SG) 18 degradation under visible light is suppressed in the presence of histidine, but it is not inhibited in the presence of triethanolamine.…”

Atomically precise metal nanoclusters for energy conversion

“…Atomically precise metal nanoclusters (NCs) have emerged as a novel frontier in electrocatalysis because of their well-defined crystallographically determined structures and unique catalytic properties (Figure 1a). [15][16][17][18][19] These NCs are characterized by molecular formulas such as Au 25 (SR) 18 , 20 Au 4 Ni 2 (SR) 8 , 21 Au 144 (SR) 60 , 22 and ClAg 14 (C CR) 12 , 23 where SR and C CR represent thiolate and alkynyl ligands, respectively. Such NCs also exhibit superior stability, which can be explained by the superatom theory.…”