High-Performance Dye-Sensitized Solar Cells Based on Colloid-Solution Deposition Planarized Fluorine-Doped Tin Oxide Substrates

Preparation of Photo-Bioelectrochemical Cells With the RC-LH Complex From Roseiflexus castenholzii

Roseiflexus castenholzii is an ancient green non-sulfur bacteria that absorbs the solar energy through bacteriochlorophylls (BChls) bound in the only light harvesting (LH) complex, and transfers to the reaction center (RC), wherein primary charge separation occurs and transforms the energy into electrochemical potentials. In contrast to purple bacteria, R. castenholzii RC-LH (rcRC-LH) does not contain an H subunit. Instead, a tightly bound tetraheme cytochrome c subunit is exposed on the P-side of the RC, which contains three BChls, three bacteriopheophytins (BPheos), two menaquinones, and one iron for electron transfer. These novel structural features of the rcRC-LH are advantageous for enhancing the electron transfer efficiency and subsequent photo-oxidation of the c-type hemes. However, the photochemical properties of rcRC-LH and its applications in developing the photo-bioelectrochemical cells (PBECs) have not been characterized. Here, we prepared a PBEC using overlapped fluorine-doped tin oxide (FTO) glass and Pt-coated glass as electrodes, and rcRC-LH mixed with varying mediators as the electrolyte. Absence of the H subunit allows rcRC-LH to be selectively adhered onto the hydrophilic surface of the front electrode with its Q-side. Upon illumination, the photogenerated electrons directly enter the front electrode and transfer to the counter electrode, wherein the accepted electrons pass through the exposed c-type hemes to reduce the excited P⁺, generating a steady-state current of up to 320 nA/cm² when using 1-Methoxy-5-methylphenazinium methyl sulfate (PMS) as mediator. This study demonstrated the novel photoelectric properties of rcRC-LH and its advantages in preparing effective PBECs, showcasing a potential of this complex in developing new type PBECs.

Enhanced Photo-Fenton Activity of SnO2/α-Fe2O3 Composites Prepared by a Two-Step Solvothermal Method

The x-SnO₂/α-Fe₂O₃ (x = 0.04, 0.07, and 0.1) heterogeneous composites were successfully prepared via a two-step solvothermal method. These composites were systematically characterized by the X-ray diffraction technique, field emission scanning electron microscopy, an energy dispersive spectrometer, X-ray photoelectron spectroscopy and a UV–visible spectrometer. It was found that SnO₂ nanoparticles were uniformly decorated on the surface of α-Fe₂O₃ particles in these heterogeneous composites. A comparative study of methylene blue (MB) photodegradation by α-Fe₂O₃ and x-SnO₂/α-Fe₂O₃ composites was carried out. All x-SnO₂/α-Fe₂O₃ composites showed higher MB photodegradation efficiency than α-Fe₂O₃. When x = 0.07, the MB photodegradation efficiency can reach 97% in 60 min. Meanwhile, the first-order kinetic studies demonstrated that the optimal rate constant of 0.07-SnO₂/α-Fe₂O₃ composite was 0.0537 min⁻¹, while that of pure α-Fe₂O₃ was only 0.0191 min⁻¹. The catalytic mechanism of MB photodegradation by SnO₂/α-Fe₂O₃ was examined. The SnO₂ can act as a sink and help the effective transfer of photo-generated electrons for decomposing hydrogen peroxide (H₂O₂) into active radicals. This work can provide a new insight into the catalytic mechanism of the photo-Fenton process.