Fast charge separation and photocurrent enhancement on black TiO2 nanotubes co-sensitized with Au nanoparticles and PbS quantum dots

Nanohollow Titanium Oxide Structures on Ti/FTO Glass Formed by Step-Bias Anodic Oxidation for Photoelectrochemical Enhancement

In this study, a new anodic oxidation with a step-bias increment is proposed to evaluate oxidized titanium (Ti) nanostructures on transparent fluorine-doped tin oxide (FTO) on glass. The optimal Ti thickness was determined to be 130 nm. Compared to the use of a conventional constant bias of 25 V, a bias ranging from 5 V to 20 V with a step size of 5 V for 3 min per period can be used to prepare a titanium oxide (TiOx) layer with nanohollows that shows a large increase in current of 142% under UV illumination provided by a 365 nm LED at a power of 83 mW. Based on AFM and SEM, the TiOx grains formed in the step-bias anodic oxidation were found to lead to nanohollow generation. Results obtained from EDS mapping, HR-TEM and XPS all verified the TiOx composition and supported nanohollow formation. The nanohollows formed in a thin TiOx layer can lead to a high surface roughness and photon absorbance for photocurrent generation. With this step-bias anodic oxidation methodology, TiOx with nanohollows can be obtained easily without any extra cost for realizing a high current under photoelectrochemical measurements that shows potential for electrochemical-based sensing applications.

Tailoring the Optical Properties of Sputter-Deposited Gold Nanostructures on Nanostructured Titanium Dioxide Templates Based on In Situ Grazing-Incidence Small-Angle X-ray Scattering Determined Growth Laws

Gold/titanium dioxide (Au/TiO₂) nanohybrid materials have been widely applied in various fields because of their outstanding optical and photocatalytic performance. By state-of-the-art polymer templating, it is possible to make uniform nanostructured TiO₂ layers with potentially large-scale processing methods. We use customized polymer templating to achieve TiO₂ nanostructures with different morphologies. Au/TiO₂ hybrid thin films are fabricated by sputter deposition. An in-depth understanding of the Au morphology on the TiO₂ templates is achieved with in situ grazing-incidence small-angle X-ray scattering (GISAXS) during the sputter deposition. The resulting Au nanostructure is largely influenced by the TiO₂ template morphology. Based on the detailed understanding of the Au growth process, characteristic distances can be selected to achieve tailored Au nanostructures at different Au loadings. For selected sputter-deposited Au/TiO₂ hybrid thin films, the optical response with a tailored localized surface plasmon resonance is demonstrated.

Preparation of ZnO/two-layer self-doped black TiO2 nanotube arrays and their enhanced photochemical properties

Highly efficient TiO₂ photoanodes can be achieved by enhancing electrical conductivity and improving charge separation and transfer. In this paper, Ti foils were used to fabricate TiO₂ nanotubes by anodic oxidation and ZnO/two-layer self-doped black TiO₂ nanotubes were prepared by electrochemical reduction and a hydrothermal method. The formed black TiO₂ nanotubes have a better photoconversion efficiency and the maximum photoconversion efficiency increased by 59% compared with the pure nanotubes. The deposition of ZnO further improves the maximum photoconversion efficiency to 456% based on black TiO₂. The photocurrent responses also increase by about 5 times in our results. This work is instructive for the development of highly robust and efficient photoanode materials in fields including photoelectrochemistry and photocatalysis.

Highly efficient TiO₂ photoanodes can be achieved by enhancing electrical conductivity and improving charge separation and transfer.

Highly stable all-in-one photoelectrochemical electrodes based on carbon nanowalls

Photoelectrochemical (PEC) cells offer a promising approach for developing low-cost solar energy conversion systems. However, the lack of stable and cost-effective electrodes remains a bottleneck that hampers their practical applications. Here, we propose a kind of integrated all-in-one three-dimensional (3D) carbon nanowall (CNW) electrode without sensitized semiconductors for stable all-carbon PEC cells. The all-in-one CNW electrodes were fabricated by directly growing CNW on both sides of the SiO₂/Si/SiO₂ wafer employing the radio frequency plasmon enhanced chemical vapor deposition method. Benefitting from the interconnected 3D textured structure, the CNW can effectively absorb the incident light and provide a large electrochemical reaction interface at the CNW surface that promotes the separation of photogenerated charge carriers, which makes it a superior electrode material. Experimental results show that the all-in-one CNW electrodes possess excellent PEC performance with a photocurrent density of 830 μA cm^-2. Moreover, the CNW electrodes exhibit excellent photoresponses over a wide waveband and superior stability with a maintained photocurrent response, even after 60 d, which outperforms the electrodes using the other two-dimensional layered materials or semiconductor sensitized electrodes. Such an all-in-one electrode with impressive photovoltaic properties provides a promising platform for PEC applications that is eco-friendly with high efficiency, excellent stability and low cost.

An Efficient Photocatalyst Based on Black TiO2 Nanoparticles and Porous Carbon with High Surface Area: Degradation of Antibiotics and Organic Pollutants in Water

Porous carbon (PC) materials with high surface area can separate electron-hole pairs and adsorb organic pollutants more effectively. A series of nanocomposites were prepared by anchoring black TiO₂ nanoparticles (BTN) onto PC through a calcination process. Chemical and structural features of samples were examined by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, powder X-ray diffraction (P-XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The resulting adsorption-photocatalysis synergistic effect led to a dramatically improved photocurrent for BTN@PCs, thus indicating the high photocatalytic performance toward water-soluble organic species. For instance, the degradation of tetracycline under visible light reached 90 %, which is higher than that for activated carbon doped onto BTN (57 %) without any additional agents. Moreover, the degradation of other antibiotics (such as oxytetracycline and ciprofloxacin) and methylene blue were also studied, thus showing that this system has the potential to be used for water treatment.