Integrated Z-Scheme Nanosystem Based on Metal Sulfide Nanorods for Efficient Photocatalytic Pure Water Splitting

Decorating Zn0.5Cd0.5S with C,N Co-Doped CoP: An Efficient Dual-Functional Photocatalyst for H2 Evolution and 2,5-Diformylfuran Oxidation

Photocatalytic H₂ evolution and biomass-derived alcohol oxidation is a cooperative way for improving the utilization of photogenerated charge carriers. Herein, a highly efficient photocatalyst was fabricated by decorating Zn_0.5Cd_0.5S with a C,N codoped CoP polyhedron (referred to as CoP, derived from ZIF-67), and then it was used for H₂ evolution and 5-hydroxymethylfurfural (HMF) oxidation. For the optimized sample (20% CoP/Zn_0.5Cd_0.5S), the generated H₂ rate is significantly enhanced from that of the HMF aqueous solution with 2,5-diformylfuran (DFF) as a concomitant product, about 31.7 times higher than the pristine Zn_0.5Cd_0.5S under visible light irradiation. The separation of photoexcited electrons (e^-) and holes (h⁺) in the process was promoted, as both e^- and h⁺ were involved in the desired conversions. From the results of density functional theory (DFT) calculations and in situ XPS spectra, the utilization of e^- was further improved as a spontaneous transfer from Zn_0.5Cd_0.5S to CoP occurred due to the p-n heterojunction formed between Zn_0.5Cd_0.5S (n type) and CoP (p type). This work provides an efficient method to separate the photoinduced charge carriers and a new way for H₂ evolution accompanied by transformation of HMF to DFF.

Construction of TiO2(B)/Anatase Heterophase Junctions via a Water-Induced Phase Transformation Strategy for Enhanced Photocatalytic Hydrogen Production

The development of facile and green solution-phase routes toward the fabrication of TiO₂-based heterophase junctions with a delicate control of phase and structure is a challenging task. Herein, we report a simple and convenient method to controllably fabricate TiO₂(B)/anatase heterophase junctions, which was successfully realized by utilizing the ideal great solvent of water to treat the presynthesized TiO₂(B) nanosheet precursor at a low temperature of 80 °C. On the basis of phase structure transformation and morphology evolution data, the formation of these TiO₂(B)/anatase heterophase junctions was reasonably explained by a novel water-induced TiO₂(B) → anatase phase transformation mechanism. Benefiting from the desirable structural and photoelectronic advantages of more exposed active sites, enhanced light absorbance, and promoted separation of photogenerated electron-hole pairs, the thus-transformed TiO₂(B)/anatase heterophase junctions exhibit fascinating photocatalytic performance in water splitting. Specifically, with the help of Pt as a cocatalyst and methanol as a sacrificial agent, the H₂ production rate of optimized TiO₂(B)/anatase heterophase junction reaches 6.92 mmol·g^-1·h^-1, which is almost 7.1 and 2.1 times higher than those of the pristine TiO₂(B) nanosheets and the final anatase nanocrystals. More interestingly, the TiO₂(B)/anatase heterophase junction also delivers prominent activity toward pure water splitting to simultaneously produce H₂ and H₂O₂, with evolution rates of up to 1.10 and 0.55 mmol·g^-1·h^-1, respectively. Our work may advance the facile green solvent-mediated synthesis of metal oxide-based heterophase junctions for applications in energy- and environmental-related areas.

In situ construction of 0D CoWO4 modified 1D Mn0.47Cd0.53S for boosted visible-light photocatalytic H2 activity and photostability

To enhance the photocatalytic activity, loading proper semiconductor with high efficiency and low cost is one of the most valid approaches. Herein, various amounts of CoWO₄ as a novel metal-free material were loaded on Mn_0.47Cd_0.53S (MCS) nanorods for photocatalytic hydrogen production reaction. The CoWO₄/Mn_0.47Cd_0.53S-25 (CW/MCS-25) exhibits the highest hydrogen production rate of 41.53 mmol·h^-1·g^-1 in the Na₂S/Na₂SO₃ system, which is about 2.68 times higher than that of pristine MCS. The Mapping and HRTEM reveals the deposited of CoWO₄ on the MCS. The detailed analyses of XPS, EIS, TRPL spectra and transient photocurrent responses indicate that CoWO₄ and MCS interacted closely and the photogenerated electrons of CoWO₄ can be transferred into MCS. In particular, the introduction of CoWO₄ can further transfer the photogenerated holes of MCS, thereby inhibiting the photocorrosion of MCS and improving photocatalytic activity. This work provides a reference for the exploration of noble metal-free composite material and shows great potential in the photocatalytic application.