Photoelectrochemistry of Au Nanocluster-Sensitized TiO₂: Intricacy Arising from the Light-Induced Transformation of Nanoclusters into Nanoparticles

Abstract

Investigating photoelectrode interfaces is challenging due to complex charge carrier pathways, and photodegradation aggravates this difficulty because interfacial properties are significantly altered by degradation. Unlike dyes and semiconductors that degrade into photoinactive materials, the photodegradation of Au nanoclusters (NCs) yields Au nanoparticles (NPs) that are photoactive. Besides, these NPs can form Schottky barriers with TiO2, which can affect interfacial band structures. Hence, the copresence of this photoactive nanoduo gives rise to unprecedented complexity in understanding the photoelectrochemical behavior of NC-sensitized photoelectrodes. In this work, we unveil that electron injection into TiO2 and subsequent electron trapping at deep surface trap states in TiO2, which are created by sensitization, play a vital role in the photodegradation. We also demonstrate that photocurrent can be enhanced through judicious control over photodegradation that would otherwise be deleterious. This photocurrent enhancement is attributed to multiple overlooked effects of Au NPs (plasmonic field enhancement and interfacial band bending).

Role of Femtosecond Pulsed Laser-Induced Atomic Redistribution in Bimetallic Au–Pd Nanorods on Optoelectronic and Catalytic Properties

“…PECs typically consist of architecturally sophisticated photoelectrocatalysts assembled into a structure designed to optimize light harvesting and catalytic chemical transformations. Physical and chemical processes critical to PEC cells’ operation occur at the electrode–electrolyte interface. − After plasmonic excitation of metal nanoparticles with incident light, the plasmon can quickly dephase through electron–surface scattering on the time scale of a few femtoseconds (fs), generating nonthermal hot electrons. After a few hundred fs, electron–electron scattering produces a distribution of electrons with temperature on the order of hundreds of degrees above the surrounding medium .…”

Significant Aggregation-Enhanced Carrier Separation in Nanoscopic Catalysts Heterojunction Stacks

“…The CB and VB positions of (AuNP/N-TN) 10 are shown in their band structure diagram in Figure h. Upon contacting, the space charge region and the energy band bend are formed around the interfacial area between Au NPs and TiO 2 . − Thus, in the statistical data relevant to electron energies, changes are observed compared with pure TiO 2 samples (Figure S4).…”

Similar Looks, Different Photoelectrochemical Behavior: Unique Aspects of Metal-Nanocluster-Sensitized Electrodes

“…Therefore, NCs must not be grouped in the same category as traditional photosensitizers. Some researchers have criticized the relatively low photostability of NCs under light irradiation, which they believe is obstructing the practical implementation of NCs in light-harvesting assemblies. − Unfortunately, the degradation mechanism of NC-sensitized photoelectrodes has also been assessed along the same lines as for traditional photoelectrodes; however, unlike QDs and dyes that degrade/decompose into photoinactive materials, the photodegradation of NCs yields plasmonic NPs that are also photoactive. − The presence of this photoactive nanoduo (one is molecular and the other is metallic) not only makes the interfacial structure of NC-sensitized electrodes more complex than that of traditional sensitized ones but also provides freedom to harness the benefits of in-situ-formed NPs in such a way that the photosensitization loss of NCs during photodegradation can be compensated. ,, Keeping these points in mind, it is necessary to present an up-to-date survey on the PEC behavior of NC-sensitized photoelectrodes in device architectures so that energy researchers no longer combine them with traditionally sensitized ones.…”