BiVO4-Deposited MIL-101-NH2 for Efficient Photocatalytic Elimination of Cr(VI)

In this study, a flower-like BiVO₄/MIL-101-NH₂ composite is synthesized by a facile and surfactant-free process. The -COO^--Bi³⁺ ionic bond construction was conductive to enhance the interface affinity between BiVO₄ and MIL-101-NH₂. Due to the highly efficient light capture and sufficient electron traps induced by oxygen vacancies and the formation of a heterostructure, the improved separation and transportation rates of charge carriers are realized. In addition, the MIL-101-NH₂/BiVO₄ composite is favorable for Cr(VI) photocatalytic removal (91.2%). Moreover, FNBV-3 (Fe/Bi = 0.25) also exhibited an excellent reusability after five cycles.

Combining Modulated Techniques for the Analysis of Photosensitive Devices

Small-perturbation techniques such as impedance spectroscopy (IS), intensity-modulated photocurrent spectroscopy (IMPS), and intensity-modulated photovoltage spectroscopy (IMVS) are useful tools to characterize and model photovoltaic and photoelectrochemical devices. While the analysis of the impedance spectra is generally carried out using an equivalent circuit, the intensity-modulated spectroscopies are often analyzed through the measured characteristic response times. This makes the correlation between the two methods of analysis generally unclear. In this work, by taking into consideration the absorptance and separation efficiency, a unified theoretical framework and a procedure to combine the spectral analysis of the three techniques are proposed. Such a joint analysis of IS, IMPS, and IMVS spectra greatly reduces the sample space of possible equivalent circuits to model the device and allows obtaining parameters with high reliability. This theoretical approach is applied in the characterization of a silicon photodiode to demonstrate the validity of this methodology, which shows great potential to improve the quality of analysis of spectra obtained from frequency domain small-perturbation methods.

Amorphous Fe(OH)3 Passivating CeO2 Nanorods: A Noble-Metal-Free Photocatalyst for Water Oxidation

Noble-metal-free composites with good photocatalytic property are of great interest. Here, CeO₂ nanorods composites loaded with amorphous Fe(OH)₃ cocatalyst were designed and prepared via a secondary water bath at 100 °C. The as-synthesized CeO₂ /amorphous Fe(OH)₃ composites exhibited superior light photocatalytic activities compared to pure CeO₂ , especially the sample with a loading time of 60 min. The photocatalytic oxygen generation rate could reach to 357.2 μmol h^-1  g^-1 , and the average apparent quantum yield (AQY) was 24.67 %, which was a 5.5-fold increase compared to the CeO₂ sample. The improvement of photocatalytic performance could be ascribed to three main reasons: First, loading the amorphous Fe(OH)₃ enlarged the specific surface area and passivated the surface of the pristine CeO₂ . Second, the amorphous Fe(OH)₃ ,which acted as a cocatalyst, provided many active sites, and reduced the reaction activation energy. Thirdly, the maximum interface with intimate contact between CeO₂ and amorphous Fe(OH)₃ cocatalyst accelerated the photogenerated charge separation efficiency and thus improved the photocatalytic performance of CeO₂ in photocatalytic water oxidation.

Construction of Defective Zinc-Cadmium-Sulfur Nanorods for Visible-Light-Driven Hydrogen Evolution Without the Use of Sacrificial Agents or Cocatalysts

Solar-driven H₂ evolution is an essential process for sustainable energy development. Currently, the greatest challenge is the development of efficient photocatalysts to drive this reaction, especially in pure water systems (without the use of a sacrificial agent). In this study, structural defects in Zn-Cd-S nanorod photocatalysts are found to increase charge separation efficiency significantly by sevenfold. Efficient H₂ evolution (352.7 μmol h^-1  g^-1 , 100 mg of catalyst) is achieved by using this defective Zn-Cd-S nanorod photocatalyst in the absence of sacrificial agents and precious metal cocatalysts under visible-light irradiation. Thus, this cocatalyst- and sacrificial-agent-free, visible-light-responsive system shows remarkable potential as a new artificial photosynthesis route for green H₂ production.

Improved Photoelectrocatalytic Performance for Water Oxidation by Earth-Abundant Cobalt Molecular Porphyrin Complex-Integrated BiVO4 Photoanode

An earth-abundant, low-cost cobalt porphyrin complex (CoTCPP) is designed as a molecular catalyst to work on three-dimensional BiVO4 film electrode for water oxidation for the first time. Under illumination of a 100 mW cm(-2) Xe lamp, the CoTCPP-functionalized BiVO4 photoanode exhibits a 2-fold enhancement in photocurrent density at 1.23 V vs RHE and nearly a 450 mV cathodic shift at 0.5 mA cm(-2) photocurrent density relative to bare BiVO4 in 0.1 M Na2SO4 (pH = 6.8). Simultaneously, stoichiometric oxygen and hydrogen are generated with a faradic efficiency of 80% over 4 h. The activity and stability of the BiVO4 photoanode are dramatically increased by molecular CoTCPP, giving rise to higher performance than previously reported noble metal ruthenium complex-modified BiVO4 photoanode. By using hydrogen peroxide as the hole scavenger, we demonstrate that molecular CoTCPP catalyst greatly suppresses the hole-electron recombination on the surface of BiVO4 semiconductor, which offers a promising route toward high efficiency, low cost, practical solar fuel generation device.

Interfacial Charge Transfer in Dye-Sensitized Solar Cells Using SCN-Free Terpyridine-Coordinated Ru Complex Dye and Co Complex Redox Couples

The efficiency of dye-sensitized solar cells (DSSCs) using Ru complex dyes and Co complex redox couples has been increased with a strategy to prevent charge recombination via the addition of bulky or lengthy peripheral units to the dyes. However, despite the efforts, most of the DSSCs are still suffering from nonunity quantum efficiency and fast recombination. We examine the effect of SCN ligand, which has been used for many Ru complex dyes and could attract positively charged Co complexes. We find that replacing the ligands with 2,6-bis(2'-(4'-trifluoromethyl)pyrazolyl)pyridine increases the quantum efficiency and electron lifetime. With the combination of the replacement of SCN ligands and the addition of bulky moiety, ∼80% external quantum efficiency is achieved. These suggest that not only the addition of a blocking effect but also the reduction of electrostatic and dispersion forces between dyes and Co complexes are essential to control the charge separation and recombination processes.