Interfacial Engineering at Quantum Dot-Sensitized TiO2 Photoelectrodes for Ultrahigh Photocurrent Generation

TiO2nanorod arrays/Ti3C2TxMXene nanosheet composites with efficient photocatalytic activity

Semiconductor photocatalysis holds significant promise in addressing both environmental and energy challenges. However, a major hurdle in photocatalytic processes remains the efficient separation of photoinduced charge carriers. In this study, TiO2nanorod arrays were employed by glancing angle deposition technique, onto which Ti3C2TxMXene was deposited through a spin-coating process. This hybrid approach aims to amplify the photocatalytic efficacy of TiO2nanorod arrays. Through photocurrent efficiency characterization testing, an optimal loading of TiO2/Ti3C2Txcomposites is identified. Remarkably, this composite exhibits a 40% increase in photocurrent density in comparison to pristine TiO2. This enhancement is attributed to the exceptional electrical conductivity and expansive specific surface area inherent to Ti3C2TxMXene. These attributes facilitate swift transport of photoinduced electrons, consequently refining the separation and migration of electron-hole pairs. The synergistic TiO2/Ti3C2Txcomposite showcases its potential across various domains including photoelectrochemical water splitting and diverse photocatalytic devices. As such, this composite material stands as a novel and promising entity for advancing photocatalytic applications. This study can offer an innovative approach for designing simple and efficient photocatalytic materials composed of MXene co-catalysts and TiO2for efficient water electrolysis on semiconductors.

Surface State-Assisted Delayed Photocurrent Response of Au Nanocluster/TiO2 Photoelectrodes

Gold nanoclusters (NCs) can be used as sensitizers to extend the absorption capabilities of TiO₂ as photoelectrodes. However, the adsorption of NCs also creates additional surface states on the TiO₂ surface, which gives rise to intricacies in the understanding of various interfacial phenomena occurring in NC-sensitized TiO₂. One of the complexities that have recently been discovered is the size-dependent hole-transfer mechanism. In this work, we reveal another anomalous behavior in the hole-transfer process that the hole scavenging ability of the electrolyte also plays a role in determining the hole-transfer mechanism in the NC-TiO₂ system, which is unprecedented in other photoelectrode systems. In the presence of an efficient hole scavenger (Na₂SO₃), the hole transfer in Au₁₈-TiO₂ occurs directly through the highest occupied molecular orbital (HOMO) of Au₁₈ NCs. However, in the presence of a less efficient hole scavenger (ethylenediaminetetraacetic acid), hole transfer in Au₁₈-TiO₂ does not occur through the HOMO and shifts to surface state-assisted hole transfer. Due to surface state charging, this surface state-assisted hole-transfer mechanism results in delayed photocurrent response in Au₁₈-TiO₂. Evidence for this exotic hole-transfer mechanism shift is provided by photoelectrochemical electrochemical impedance spectroscopy, and its implications are discussed.

Bioinspired Compound Eyes for Diffused Light-Harvesting Application

Natural compound eyes endow arthropods with wide-field high-performance light-harvesting capability that enables them to capture prey and avoid natural enemies in dim light. Inspired by natural compound eyes, a curved artificial-compound-eye (cACE) photodetector for diffused light harvesting is proposed and fabricated, and its light-harvesting capability is systematically investigated. The cACE photodetector is fabricated by introducing a cACE as a light-harvesting layer on the surface of a silicon-based photodetector, with the cACE being prepared via planar artificial-compound-eye (pACE) template deformation. The distinctive geometric morphology of the as-prepared cACE effectively reduces its surface reflection and the dependence of the projected area on the incident light direction, thereby significantly improving the light-harvesting ability and output photocurrent of the silicon-based photodetector. Furthermore, the performances of cACE, pACE, and bare polydimethylsiloxane (PDMS)-attached photodetectors as diffused light detectors are investigated under different luminances. The cACE-photodetector output photocurrent is 1.395 and 1.29 times those of the bare PDMS-attached and pACE photodetectors, respectively. Moreover, this photodetector has a desirable geometric shape. Thus, the proposed cACE photodetector will facilitate development of high-performance photodetectors for luminance sensing.