One-pot molten salt method for constructing CdS/C3N4 nanojunctions with highly enhanced photocatalytic performance for hydrogen evolution reaction

Structure-phase transformation of bismuth oxide to BiOCl/Bi24O31Cl10 shoulder-by-shoulder heterojunctions for efficient photocatalytic removal of antibiotic

Developing heterojunction photocatalyst with well-matched interfaces and multiple charge transfer paths is vital to boost carrier separation efficiency for photocatalytic antibiotics removal, but still remains a great challenge. In present work, a new strategy of chloride anion intercalation in Bi2O3 via one-pot hydrothermal process is proposed. The as-prepared Ta-BiOCl/Bi24O31Cl10 (TBB) heterojunctions are featured with Ta-Bi24O31Cl10 and Ta-BiOCl lined shoulder-by-shouleder via semi-coherent interfaces. In this TBB heterojunctions, the well-matched semi-coherent interfaces and shoulder-by-shoulder structures provide fast electron transfer and multiple transfer paths, respectively, leading to enhanced visible light response and improved photogenerated charge separation. Meanwhile, a type-II heterojunction for photocharge separation has been obtained, in which photogenerated electrons are drove from the CB (conduction band) of Ta-Bi24O31Cl10 to the both of bilateral empty CB of Ta-BiOCl and gathered on the CB of Ta-BiOCl, while the photogenerated holes are left on the VB (valence band) of Ta-Bi24O31Cl10, effectively hindering the recombination of photogenerated electron-hole pairs. Furthermore, the separated electrons can effectively activate dissolved oxygen for the generation of reactive oxygen species (·O2-). Such TBB heterojunctions exhibit remarkably superior photocatalytic degradation activity for tetracycline hydrochloride (TCH) solution to Bi2O3, Ta-BiOCl and Ta-Bi24O31Cl10. This work not only proposes a Ta-BiOCl/Bi24O31Cl10 shoulder-by-shoulder micro-ribbon architectures with semi-coherent interfaces and successive type-II heterojunction for highly efficient photocatalytic activity, but offers a new insight into the design of highly efficient heterojunction through phase-structure synergistic transformation strategy.

In Situ Construction of CdS/g-C3N4 Heterojunctions in Spent Thiolation@Wood-Aerogel for Efficient Excitation Peroxymonosulfate to Degradation Tetracycline

Pollutant treatment, hazardous solid waste conversion, and biomass resource utilization are significant topics in environmental pollution control, and simultaneously achieving them is challenging. Herein, we developed a "from waste absorbent to effective photocatalyst" upcycle strategy for nontoxic conversion of Cd(II) adsorbed on thiolation@wood-aerogel (TWA) into CdS/g-C3N4 heterojunctions through the in situ chemical deposition high-temperature carbonization combined conversion method to overcome the above problems simultaneously. We used Schiff base reaction to graft l-cysteine into dialdehyde@wood-aerogel to prepare TWA with a high Cd(II) adsorption capacity (600 mg/L, 294.66 mg/g). Subsequently, the spent Cd(II)-loaded-TWA was used as a substrate for in situ construction of Cd(II) into CdS/g-C3N4 heterojunction for activating peroxymonosulfate (PMS) under simulated sunlight [simulated solar light (SSL)], achieving efficient tetracycline (TC) degradation (20 mg/L, 95.32%). The Langmuir and pseudo-second-order models indicate single-layer chemical adsorption of Cd(II) on the TWA adsorption process. In the PMS/SSL system, CdS/g-C3N4@TWA efficiently and rapidly degraded TC via an adsorption-photocatalytic synergistic degradation mechanism. The used CdS/g-C3N4@TWA has a good biocompatibility. This study proposed design and preparation of a new type of wood aerogel absorbent and provided a novel upcycling strategy for innovative use of the spent waste adsorbent.

Preparation of S-C3N4/AgCdS Z-Scheme Heterojunction Photocatalyst and Its Effectively Improved Photocatalytic Performance

In this study, S-doped graphitic carbon nitride (S-C3N4) was prepared using the high-temperature polymerization method, and then S-C3N4/AgCdS heterojunction photocatalyst was obtained using the chemical deposition method through loading Ag-doped CdS nanoparticles (AgCdS NPs) on the surface of S-C3N4. Experimental results show that the AgCdS NPs were evenly dispersed on the surface of S-C3N4, indicating that a good heterojunction structure was formed. Compared to S-C3N4, CdS, AgCdS and S-C3N4/CdS, the photocatalytic performance of S-C3N4/AgCdS has been significantly improved, and exhibits excellent photocatalytic degradation performance of Rhodamine B and methyl orange. The doping of Ag in collaboration with the construction of a Z-scheme heterojunction system promoted the effective separation and transport of the photogenerated carriers in S-C3N4/AgCdS, significantly accelerated its photocatalytic reaction process, and thus improved its photocatalytic performance.

The Synergistic Effect in CdS/g-C3N4 Nanoheterojunctions Improves Visible Light Photocatalytic Performance for Hydrogen Evolution Reactions

This study focuses on the development of heterojunction photocatalysts for the efficient utilization of solar energy to address the energy crisis and reduce environmental pollution. Cadmium sulfide (CdS)/graphite-type carbon nitride (g-C3N4) nanocomposites were synthesized using a hydrothermal method, and their photoelectrochemical properties and photocatalytic performance for hydrogen evolution reaction (HER) were characterized. Scanning electron microscope images showed the intimate interface and caviar-like nanoheterojunction of the CdS nanoparticles on g-C3N4 nanospheres, suggesting their potential involvement in the photocatalytic process. Electrochemical and spectroscopic analyses were conducted to confirm the roles of CdS in the nanoheterojunction. The results showed that 10 wt% CdS/g-C3N4 nanospheres exhibited higher photocatalytic activity than pure g-C3N4 under visible light irradiation. A HER rate of 655.5 μmol/g/h was achieved after three photocatalytic cycles, signifying good photocatalytic stability. The synergistic effect of the Z-scheme heterojunction formed by g-C3N4 and CdS was identified as the main factor responsible for the enhanced photocatalytic performance and stability. The interface engineering effect of CdS/g-C3N4 facilitated the separation of photogenerated electrons and holes. This study provides insights into the design and fabrication of efficient HER photocatalysts.

Effect of molten-salt modulation on the composition and structure of g-C3N4-based photocatalysts

Graphitic carbon nitride (g-C3N4), as an attractive metal-free polymer photocatalyst, has attracted extensive attention in energy and environmental fields in recent years. The photoactivity of bulk g-C3N4 is moderate on account of solid-phase thermal-condensation synthesis. This leads to inadequate light absorption, limited surface area, and easy recombination of charge carriers. The composition and nanostructure of g-C3N4 have been studied extensively. Molten-salt modulation is fascinating because of its "green" credentials and the properties of liquid-phase reaction systems. The review focuses mainly on molten-salt modulation of the composition and structure of g-C3N4 based-photocatalysts. We focus on elemental doping, molecular doping, and defect engineering, as well as control of the crystal structure, multi-dimensional structure, hom/heterostructures for photocatalytic applications. This review provides new insights to develop g-C3N4-based photocatalysts with control of composition and structure by facile molten-salt modulation in energy-conversion and environmental fields.

ReS2 with unique trion behavior as a co-catalyst for enhanced sunlight hydrogen production

The interfacial catalytic reaction plays a crucial role in determining hydrogen production efficiency of a photocatalyst. In this work, hollow spherical nano-shell composite (g-C₃N₄/CdS/ReS₂) formed by graphitic carbon nitride (g-C₃N₄), cadmium sulfide (CdS), and rhenium disulfide (ReS₂) was prepared for photocatalytic hydrogen production, with ReS₂ introduced as a relatively inexpensive co-catalyst with excellent performance. It was found that two-electron catalytic reaction took place in this photocatalytic system due to the unique trion behavior of ReS₂ co-catalyst, which greatly enhances the rate of photocatalytic hydrogen production. The tightly bound excitons in the ReS₂ co-catalyst could easily capture the photogenerated electrons in the photocatalytic system to form trions, while g-C₃N₄ in the inner shell and CdS in the middle shell provided sufficient electrons for the formation of trions. The active edge sites of ReS₂ also facilitated the generation and desorption of hydrogen, which creates conditions favoring two-electron catalytic reaction. In addition, oxidation and reduction reactions occurred inside and outside of the hollow spherical nano-shell, respectively, which effectively inhibits the recombination of photogenerated carriers. The unique trion behavior of ReS₂ alters the interfacial catalytic reaction compared to the widely used platinum (Pt) co-catalyst in photocatalytic hydrogen production, which provides a new approach for enhancing the activity of photocatalytic systems.

1D CdS modified 3D zinc cobalt oxide heterojunctions boost solar-driven photocatalytic performance

In the process of photocatalysis, semiconductor materials generate photogenerated electrons and photogenerated holes when excited by sunlight, so as to participate in the process of photocatalytic decomposition of water to produce hydrogen.

CuS/Ag2O nanoparticles on ultrathin g-C3N4 nanosheets to achieve high performance solar hydrogen evolution

Ternary heterostructures play a crucial role in improving the separation of charge carriers and fast surface reaction kinetics, which in turn helps in understanding the effective photocatalytic water splitting performance. Herein, CuS/Ag₂O nanoparticles were presented on a graphitic carbon nitride (g-C₃N₄) surface to obtain CuS/Ag₂O/g-C₃N₄ material using facile hydrothermal and precipitation methods. Structural and morphological studies confirmed the presence of ternary nanostructures comprising CuS, Ag₂O, and g-C₃N₄ with nanoparticle and nanosheet morphologies. The as-synthesized CuS/Ag₂O/g-C₃N₄ exhibited a remarkable photocatalytic H₂ production of 1752 µmol.h^-1.g^-1_cat, which is considerably superior than those of CuS and g-C₃N₄. The improved H₂ production performance which is due to the effective interfacial CuS/Ag₂O/g-C₃N₄ heterojunction interface and superior hole (h⁺) trapping capability of the CuS at the CuS/Ag₂O/g-C₃N₄ interface. This can efficiently enhance the lifetime of photoexcited charge carriers and enhance the electron density for the production of H₂. The optimum CuS/Ag₂O/g-C₃N₄ heterostructure remained stable after 8 successive experimental cycles, although with a slight change in the H₂ production rate. Therefore, this study offers a novel approach to exploit the efficacy through the synergetic effect of integrating CuS as the photocatalyst and Ag₂O as the visible sensitizer, thus proposing a viable strategy of using earth-abundant material to enhance the conversion of solar energy to fuel.

Electrochromic properties of pyrene conductive polymers modified by chemical polymerization

Pyrene is composed of four benzene rings and has a unique planar melting ring structure. Pyrene is the smallest condensed polycyclic aromatic hydrocarbon, and its unique structural properties have been extensively studied. Pyrene has excellent properties such as thermal stability, high fluorescence quantum efficiency and high carrier mobility. This paper mainly used thiophene, EDOT and triphenylamine groups to enhance the pyrene based π-conjugated system and control the molecular accumulation of organic semiconductors, and improve their charge transport performances. Five kinds of polymer were synthesized and correspondingly characterized. The five kinds of pyrene conductive polymer had outstanding properties in terms of solubility, fluorescence intensity and thermal stability, good film-forming properties, stable electrochromic properties and high coloring efficiency. The coloration efficiency (CE) of PPYTP was as high as 277 cm² C⁻¹, and the switching response time was short. The coloring time of PPYEDOT was 1.3 s and the bleaching time was 3.2 s. The lower impedance will also provide the possibility of such polymers being incorporated into electrochromic devices in the future. In short, the synthesized new pyrene conductive polymers will have wide application prospects in the field of electrochromic materials.

Pyrene is composed of four benzene rings and has a unique planar melting ring structure.