Engineering Mn-Doped CdS Thin Films Through Chemical Bath Deposition for High-Performance Photoelectrochemical Water Splitting

Doping conventional materials with a second element is an exciting strategy for enhancing catalytic performance via electronic structure modifications. Herein, Mn-doped CdS thin films were successfully synthesized with the aid of the chemical bath deposition (CBD) by varying the pH value (8, 10, and 12) and the surfactant amount (20, 40, 60 mg). Different morphologies like nano-cubes, nanoflakes, nano-worms, and nanosheets were obtained under different deposition conditions. The optimized Mn-doped CdS synthesized at pH=8 exhibited better photoelectrochemical (PEC) performance for oxygen evolution reaction (OER) than pure CdS films, with a maximum photocurrent density of 300 μA/cm2 at an external potential of 0.5 V, under sunlight illumination. The observed performance is attributed to the successful Mn doping, porosity, high surface area, and nanosphere morphology.

The precursor-guided hydrothermal synthesis of CuBi2O4/WO3 heterostructure with enhanced photoactivity under simulated solar light irradiation and mechanism insight

Z-scheme heterojunction can efficiently suppress the electron-holes recombination and promote the charges transfer rate, which result in the high photocatalytic performance. Herein, a flower-flake-sphere like CuBi₂O₄/WO₃ hybrid photocatalyst was fabricated via a precursor-guided hydrothermal method. The morphology, structure, composition, chemical and electronic properties of the as-prepared samples were systematically investigated by multiple techniques (XRD, FT-IR, SEM, TEM, XPS, UV-vis, BET, PL, ESR. etc.). Particularly, the 60 wt% CuBi₂O₄/WO₃ nanocomposite exhibited the highest photocatalytic activity for tetracycline (20 mg/L) degradation under simulated solar light irradiation. The rate constant was 0.0179 min^-1, which was almost 8 times and 4.5 times higher than that of bulk WO₃ and CuBi₂O₄, respectively. The experimental results confirmed that CuBi₂O₄ made a direct Z-scheme heterojunction by band alignment with WO₃, which are conducive to the efficient charges separation and prolonged carriers lifetime. According to the quenching experiments, •OH and •O₂- were testified to be the predominant active species. The electrons accumulated in the CuBi₂O₄ negative CB and the holes in the WO₃ positive VB made significant contribution to the strong redox ability of the CuBi₂O₄/WO₃ nanocomposite. This work provides some deep insights into the design of band-alignment-based Z-scheme heterostuctures, which is also applicable to other catalytic system.

WO3/Conducting Polymer Heterojunction Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting

An efficient and stable heterojunction photoanode for solar water oxidation was fabricated by hybridization of WO₃ and conducting polymers (CPs). Organic/inorganic hybrid photoanodes were readily prepared by the electropolymerization of various CPs and the codeposition of tetraruthenium polyoxometalate (Ru₄POM) water-oxidation catalysts (WOCs) on the surface of WO₃. The deposition of CPs, especially polypyrrole (PPy) doped with Ru₄POM (PPy:Ru₄POM), resulted in a remarkably improved photoelectrochemical performance by the formation of a WO₃/PPy p-n heterojunction and the incorporation of efficient Ru₄POM WOCs. In addition, there was also a significant improvement in the photostability of the WO₃-based photoanode after the deposition of the PPy:Ru₄POM layer due to the suppression of the formation of hydrogen peroxide, which was responsible for corrosion. This study provides insight into the design and fabrication of novel photosynthetic and photocatalytic systems with excellent performance and stability through the hybridization of organic and inorganic materials.

Enhanced photoelectrochemical water splitting of CrTiO2 nanotube photoanodes by the decoration of their surface via the photodeposition of Ag and Au

Photoelectrochemical water splitting of CrTiO₂ nanotube arrays decorated with loading-controllable Ag and Au by the photodeposition method.

CdTe-Based Photoanode for Oxygen Evolution from Water under Simulated Sunlight

This study investigated the properties of a photoanode fabricated by depositing a p-type CdTe thin film on a CdS-coated FTO substrate (CdTe/CdS/FTO) via close-space sublimation. This CdTe/CdS/FTO electrode was found to work as a photoanode with a long absorption edge wavelength of 830 nm. In a CdTe-based photoanode such as this, the p-n junction formed at the CdTe/CdS interface promotes charge separation of photoexcited carriers and forces photogenerated holes to move toward the photoanode surface to promote oxidation reactions on the electrode surface. A MoO_x buffer layer was also found to play a crucial role in facilitating the transfer of photogenerated holes to surface reaction sites through decreasing the energy barrier at the interface between the CdTe and a surface protective layer. A biphotoelectrode photoelectrochemical cell composed of a CdTe-based photoanode and a CdTe-based photocathode exhibited a solar-to-hydrogen conversion efficiency of 0.22% without an external voltage in response to illumination by AM 1.5G light.

Fabrication, characterization and photoelectrochemical activity of tungsten-copper co-sensitized TiO2 nanotube composite photoanodes

Tungsten-copper co-sensitized TiO₂ nanotube films on titanium substrate, used as photoanodes in photoelectrochemical (PEC) water splitting to produce hydrogen, have been synthesized via anodization and chemical bath deposition (CBD) methods. Field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to study the morphology and elemental composition of the synthetic samples. UV-Vis diffuse reflection spectroscopy (UV-Vis DRS) was sued to investigate the optical features of the samples. The impact of copper and tungsten ratio on the photocatalytic behavior of co-sensitized TiO₂ nanotube photoelectrodes in PEC water splitting has been investigated. High photocatalytic activity has been exhibited by the co-sensitized TiO₂ nanotube samples due to the synergistic effects of the copper and tungsten. Sample T4 had the highest photoelectrochemical activity compared with other samples. In addition, this sample exhibited outstanding photochemical stability even after four runs in the photocatalytic test. A simple method for the synthesis of high performance co-sensitized TiO₂ nanotube photocatalysts for application in solar energy conversion has thus been proposed in this work. The advantages of these new photoanodes for practical applications are low cost, ease of synthesis, high activity in visible light and excellent stability.