Co2P nanosheet cocatalyst-modified Cd0.5Zn0.5S nanoparticles as 2D-0D heterojunction photocatalysts toward high photocatalytic activity

Reasonable decoration of CuO/Cd0.5Zn0.5S nanoparticles onto flower-like Bi5O7I as boosted step-scheme photocatalyst for reinforced photodecomposition of bisphenol A and Cr(VI) reduction in wastewater

Building S-scheme heterostructures is a sophisticated approach to receiving outstanding catalysts for environmental detoxification. Herein, ternary CuO/Cd0.5Zn0.5S/Bi5O7I (CO/CZS/BOI) nanocomposites were constructed by in-situ decorating of CuO and Cd0.5Zn0.5S nanoparticles onto Bi5O7I micro-sphere in a facile route. The optimal CO/CZS/BOI reflected reinforced bisphenol A (BPA) photo-oxidation (95% in 70 min) and Cr(VI) photo-reduction (96.6 in 60 min) under visible light. Besides, CO/CZS/BOI afforded 5.10 (4.44), 4.42 (3.71), and 6.60 (5.27) fold reinforcement in the BPA (Cr(VI)) photo-reaction rate compared to BOI, CZS, and CO, respectively. This behavior was linked to the development of S-scheme mechanisms resulting from the co-effects of BOI, CZS, and CO in retaining the optimum redox capacity, facilitating the dissolution of photo-carriers, increasing reactive sites, and strengthening the visible-light response. The parameters influencing the catalytic reaction of CO/CZS/BOI, such as light intensity, catalyst dosage, and pH, were deeply studied. The quenching tests declared the prominent roles •O2- and •OH in the breaking down of BPA and the participation of electrons and •O2- in the photocatalytic conversion of Cr(VI). The cyclic tests verified the robust photostability of CO/CZS/BOI, which is associated with the reintegration process between the free h+ coming from CZS and the photo-induced e- of CO and BOI in the S-scheme system. In conclusion, the present study provides a profound understanding of the photo-reaction mechanism of CO/CZS/BOI and introduces a novel concept for constructing a superior dual-Scheme system for efficient wastewater detoxification.

Design and construction of a robust ternary Bi5O7I/Cd0.5Zn0.5S/CuO photocatalytic system for boosted photodegradation of antibiotics via dual-S-scheme mechanisms: Environmental factors and degradation intermediates

The detection of efficacious and environment-friendly nanomaterials with prominent photocatalytic performance is crucial for the detoxification of antibiotics in wastewater. Herein, a dual-S-scheme Bi5O7I/Cd0.5Zn0.5S/CuO semiconductor was designed and fabricated via a simple approach to degrade tetracycline (TC) and other types of antibiotics under LED illumination. However, Cd0.5Zn0.5S and CuO nanoparticles were decorated on the surface of the Bi5O7I microsphere to create a dual-S-scheme system that stimulates visible-light utilization and facilitates the dissolution of excited photo-curriers. Therefore, the Bi5O7I/Cd0.5Zn0.5S/CuO system offers strong redox ability, which reflects reinforced photocatalytic activity and robust stability. The ternary heterojunction discloses enhanced TC detoxification efficiency of 92% in 60 min with TC destruction rate constant of 0.04034 min-1, outperforming pure Bi5O7I, Cd0.5Zn0.5S, and CuO by 4.27, 3.20, and 4.80 folds, respectively. Besides, Bi5O7I/Cd0.5Zn0.5S/CuO manifests outstanding photo-activity against a series of antibiotics like norfloxacin, enrofloxacin, ciprofloxacin, and levofloxacin under the same operational conditions. The active species detection, TC destruction pathways, catalyst stability, and photoreaction mechanisms of Bi5O7I/Cd0.5Zn0.5S/CuO were accurately explained in detail. Summarily, this work introduces a new class of dual-S-scheme system with strengthened catalytic properties to effectively eliminate the antibiotics in wastewater under visible-light illumination.

Construction of shell-core Co2P/Cd0.9Zn0.1S photocatalyst by electrostatic attraction for enhancing H2 evolution

Solar energy-driven photocatalytic decomposition of water to produce H₂ is of great significance for promoting the development of clean energy. To improve the efficiency of H₂ production, a novel spherical Co₂P/Cd_0.9Zn_0.1S (Co₂P/CZS) composite with shell-core structure was successfully synthesized by electrostatic attraction. Under visible light irradiation, the optimal Co₂P/CZS achieves an excellent H₂ rate of 16.05 mmol h^-1 g^-1 in benzyl alcohol (PhCH₂OH) solution, with a quantum efficiency of 34.3% at 450 nm. The Co₂P thin layer coated on the CZS surface not only facilitates the photogenerated charge transfer from Co₂P to CZS under visible light illumination, but reduces the energy barrier of PhCH₂OH oxidation and H₂ evolution. The present results show that shell-core Co₂P/CZS composite may be one of promising catalyst to enhance the activity of H₂ evolution, which provides an important reference basis for new catalyst design and wide prospects for further application of metal sulfides.

Incorporating Ni-Polyoxometalate into the S-Scheme Heterojunction to Accelerate Charge Separation and Resist Photocorrosion for Promoting Photocatalytic Activity and Stability

The emerging polyoxometalate (POM) nanomaterials are transition metal oxygen anion clusters with d⁰ electronic configurations, which could be attractive and potential photocatalysts. Hence, a nickel (Ni)-substituted polyoxometalate K₆Na₄[Ni₄(H₂O)₂(PW₉O₃₄)₂]·32H₂O (Ni₄POM)-incorporating step (S)-scheme heterojunction was developed to promote photocatalytic activity and stability in H₂ and H₂O₂ production. The multielectron transfer through variable valence metal centers in Ni₄POM would facilitate the recombination of invalid charges through the S-scheme pathway. Moreover, incorporating Ni₄POM into the S-scheme heterojunction can broaden the light absorption range and meanwhile lead to resistance to photocorrosion to promote the optical and chemical stability of Cd_0.5Zn_0.5S (CZS). The optimized CZSNi-70 exhibited a H₂ evolution rate of 42.32 mmol g^-1 h^-1 under visible-light irradiation with an apparent quantum yield of 32.27% at 420 nm and a H₂O₂ production rate of 295.4 μmol L^-1 h^-1 under 420 nm light-emitting diode irradiation. This work can provide a new view for the development of transition metal-substituted POM-based stable and efficient S-scheme photocatalysts.

Amorphous CoSx decorated Cd0.5Zn0.5S with a bulk-twinned homojunction for efficient photocatalytic hydrogen evolution

Amorphous CoSx was combined with Twinned-Cd0.5Zn0.5S to construct homo-heterojunction for efficient photocatalytic H2 evolution. This work provides new ideas for constructing noble metal-free photocatalyst with homo-heterojunction.

Lattice-Matched CoP/CoS2 Heterostructure Cocatalyst to Boost Photocatalytic H2 Generation

Transition-metal phosphides and sulfides are considered as promising cocatalysts for the photocatalytic hydrogen evolution reaction (HER), and the cocatalytic effect can be improved by directed heterostructure engineering. In this study, a novel lattice-matched CoP/CoS₂ heterostructure having a nanosheet morphology was developed as an HER cocatalyst and integrated in situ onto graphitic carbon nitride (g-C₃N₄) nanosheets via a successive phosphorization and vulcanization route. First-principles density functional theory calculations evidenced that the construction of the lattice-matched CoP/CoS₂ heterostructure resulted in the redistribution of interface electrons, enhanced metallic characteristics, and improved H* adsorption. As a result of these effects, the CoP/CoS₂ heterostructure cocatalyst formed a 2D/2D Schottky junction with the g-C₃N₄ nanosheets, thus promoting photoelectron transfer to CoP/CoS₂ and realizing fast charge-carrier separation and good HER activity. As expected, the CoP/CoS₂ heterostructure exhibited excellent cocatalytic activity, and the optimal loading of the cocatalyst on g-C₃N₄ enhanced its HER activity to 3.78 mmol g^-1 h^-1. This work furnishes a new perspective for the development of highly active noble-metal-free cocatalysts via heterostructure engineering for water splitting applications.

Nickel hydroxide as a non-noble metal co-catalyst decorated on Cd0.5Zn0.5S solid solution for enhanced hydrogen evolution

The study of non-noble metal photocatalysts provides practical significance for hydrogen evolution applications. Herein, new Cd_0.5Zn_0.5S/Ni(OH)₂ catalysts were fabricated through simple hydrothermal and precipitation methods. The photocatalytic performance of the Cd_0.5Zn_0.5S/Ni(OH)₂ composites under visible light was significantly improved, which was attributed to the wider visible light absorption range and less recombination of electron–hole pairs. The composite with a Ni(OH)₂ content of 10% showed the best hydrogen evolution rate of 46.6 mmol g⁻¹ h⁻¹, which was almost 9 times higher than that of pristine Cd_0.5Zn_0.5S. The severe photo-corrosion of Cd_0.5Zn_0.5S was greatly improved, and the Cd_0.5Zn_0.5S/Ni(OH)₂ composite exhibited a very high hydrogen evolution rate after three repeated tests. The excellent photocatalytic performance was due to the non-noble metal Ni(OH)₂ co-catalyst. The excited electrons were transferred to the co-catalyst, which reduced electron–hole recombination. Moreover, the co-catalyst offered more sites for photocatalytic reactions. This study researched the mechanism of a co-catalyst composite, providing new possibilities for non-noble metal photocatalysts.

This study researched the mechanism of a co-catalyst composite, providing new possibilities for non-noble metal photocatalysts.