Intrinsic Mechanism Analyses of Significantly Enhanced Photoelectrochemical Performance of the Bi2MoO6/BiVO4 System

Construction of CoSe2/WO3@Si Multiheterojunctions for Efficient Photoelectrochemical Water Splitting

Developing efficient photoanodes for photoelectrochemical (PEC) water splitting is crucial for solar-to-hydrogen energy conversion. Monocrystalline silicon, as a photoelectrode material, has limitations of high surface reflectivity, easy formation of oxide passivation, and instability in aqueous solutions. Herein, flower cluster CoSe2 and lamellar WO3 obtained via the solvothermal method are coated onto the surface of textured silicon by chemical bath deposition to prepare a multiheterojunction structured photoanode. The as-prepared CoSe2/WO3@Si-9 photoelectrode exhibits a desirable photocurrent of 10.1 mA cm-2 at 1.23 VRHE under simulated solar irradiation (AM 1.5G, 100 mW cm-2) in comparison to WO3@Si (0.49 mA cm-2) and CoSe2@Si (1.56 mA cm-2) and excellent stability over 10 h. The improved PEC hydrogen evolution performance comes from the synergistic effect of the multiple heterojunctions of CoSe2/WO3@Si composites. The synergistic effect can improve the separation efficiency of photogenerated electron-hole pairs while maintaining strong redox capability. The CoSe2/WO3@Si-9 photoanode exhibits a high photocurrent density and stability, making it a promising candidate for practical applications.

Selective Oxidation of Alcohol to Valuable Aldehydes Using Water as a Promoter in a Photoelectrochemical Cell

Artificial photoelectrochemistry (PEC) has emerged as a promising and efficient technology for the sustainable conversion of solar energy into chemicals. In this study, we present a refined PEC process that enables the highly selective and stable production of piperonal and other valuable aldehydes through the oxidation of the corresponding alcohols. By employing Fe2O3 or TiO2 as the photoanode material and 2,2,6,6-tetramethylpiperidinooxy (TEMPO) as a redox mediator in an H2O/acetonitrile solution, we achieve 100% selectivity and a >95% Faradaic efficiency for piperonal production from piperonyl alcohol (PA) oxidation. Remarkably, we reveal the enhancing effect on the PA oxidation reactivity of appropriate-amount water in the solvent as it plays a crucial role in inhibiting the photoelectron-hole recombination efficiency and facilitating charge transfer. Mechanistic analysis suggests that TEMPO-mediated PA oxidation involves the formation of •O2- radicals by the reduction of oxygen on the cathode, resulting in water as the sole byproduct. Furthermore, our PEC oxidation system exhibits applications on the 100%-selective production of various conjugated aldehydes, including 4-anisaldehyde, cuminaldehyde, and the vitamin B6 derivative. By implementing a TiO2//Fe2O3 dual-photoanode system, we achieve an enhanced piperonal production rate of 31.2 μmol h-1 cm-2 at 1.0 V vs Ag/Ag+ and demonstrate its stability over a 102 h cyclic test, ensuring near-quantitative yield. This research illuminates the potential of the PEC strategy as a generally applicable method for the efficient production of high-value aldehydes.

One-step fabrication of Cu-doped Bi2MoO6 microflower for enhancing performance in photocatalytic nitrogen fixation

This study enhances the photocatalytic N₂ immobilization performance of Bi₂MoO₆ through Cu doping. Cu-doped Bi₂MoO₆ was synthesized via a simple solvothermal method. Various characterizations were implemented to examine the influence of Cu doping on the properties of Bi₂MoO₆. Results indicated that the doped Cu element had a valence state of + 2 and substituted the position of Bi³⁺. Cu doping exerted minimal effect on the morphology of Bi₂MoO₆ but largely influenced the energy band structure. The band gap was slightly narrowed, and the conduction band was raised, such that Cu-doped Bi₂MoO₆ could generate more electrons with stronger reducibility. Moreover, importantly, Cu doping reduced work function and improved charge separation efficiency, which was considered the major cause of enhanced photoactivity. In addition, the Cu-Bi₂MoO₆ catalyst exhibited higher capability in the adsorption and activation of N₂. Under the combined effects of the aforementioned changes, Cu-Bi₂MoO₆ demonstrated considerably higher photocatalytic efficiency than Bi₂MoO₆. The optimized NH₃ generation rate reached 302 μmol/L g^-1h^-1 and 157 μmol/L g^-1h^-1 under simulated solar light and visible light, respectively, both achieving about 2.2 times higher than that of Bi₂MoO₆. This work provides a successful example of improving photocatalytic N₂ fixation, and it may show some light on the design and preparation of heteroatom-doped semiconductor photocatalysts for N₂-to-NH₃ conversion.

Nanosheets loaded on tetrahedral surfaces form a Z-type Bi2MoO6/γ-Bi2O3 heterojunction to enhance the photocatalytic degradation activity of lomefloxacin and Rhodamine B

Nanosheets loading on tetrahedral surfaces of a Bi2MoO6/γ-Bi2O3 heterojunction forming a Z-type energy band to enhance the photocatalytic degradation activity.