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As a low-cost, low toxicity and metal-free catalyst with strong light absorption, graphitic carbon nitride (g-C3N4)-based materials have gained wide attention for efficient H2O2 photocatalysis. However, further investigation regarding the charge transfer process and reaction mechanism of H2O2 photoproduction remains to be completed. In this work, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTDA) modified g-C3N4 is synthesized through a facile one-step dehydration process, and the H2O2 photoproduction could reach 22.5 μmol within 8 hours. The proposed structure of g-BTDA is confirmed by FTIR, XPS and SEM studies. The transient absorption reveals a 20.88 ps charge transfer process caused by the electron withdrawing ability of the C＝O group, and a 2-electron oxygen reduction pathway is proposed. Our work represents a new strategy for efficient H2O2 photoproduction using easily acquired materials with future application potential. [ABSTRACT FROM AUTHOR]

As a low-cost, low toxicity and metal-free catalyst with strong light absorption, graphitic carbon nitride (g-C3N4)-based materials have gained wide attention for efficient H2O2 photocatalysis. However, further investigation regarding the charge transfer process and reaction mechanism of H2O2 photoproduction remains to be completed. In this work, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTDA) modified g-C3N4 is synthesized through a facile one-step dehydration process, and the H2O2 photoproduction could reach 22.5 μmol within 8 hours. The proposed structure of g-BTDA is confirmed by FTIR, XPS and SEM studies. The transient absorption reveals a 20.88 ps charge transfer process caused by the electron withdrawing ability of the C＝O group, and a 2-electron oxygen reduction pathway is proposed. Our work represents a new strategy for efficient H2O2 photoproduction using easily acquired materials with future application potential. [ABSTRACT FROM AUTHOR]

Abstract: An Ag2S@MoS2 core–shell nanowire heterojunction, facilely synthesized by simultaneous sulfuration of Ag nanowires (NMs) and growth of MoS2, is used as a model system to disclose how the surface and interface structures influence the photocatalytic activity. The Ag2S@MoS2 NWs with different loading amounts of MoS2 are used as photocatalysts for H2 production. It is found that the highest photocatalytic activity is realized by a moderate loading amount of MoS2. A lower loading amount of MoS2 not only reduces the interfacial contact for insufficient electron–hole separation but also decreases the number of catalytic active sites for H2 production, while a higher loading amount of MoS2 increases the light‐shielding effect of Ag2S and extends the distance of electron transfer to the catalytic active sites for H2 production. Furthermore, with the same loading amount of MoS2, Ag2S@MoS2 NWs also exhibit superior H2 production activity in comparison with pre‐Ag2S@MoS2 NWs with MoS2 grown on pre‐synthesized Ag2S nanowires. The proposed reason is that the simultaneous sulfuration of Ag nanowires and growth of MoS2 results in an intimate contact between Ag2S and MoS2 for smooth interfacial charge transfer, while the two‐step synthetic method leads to a lower quality of the MoS2‐Ag2S interface and thus poor interelectron transfer. This work highlights the importance of a rational surface and interface design of semiconductor heterojunctions for realizing high‐performance photocatalytic applications. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs)/g-C3N4 is a promising photocatalyst to split water for H2 production; however, the synthesis of CDs/g-C3N4 is usually rigorous and involves multiple steps, which limits its practical application. In this study, a facile hydrothermal approach was developed to prepare CDs/g-C3N4 photocatalysts using l-ascorbic acid and g-C3N4 as the precursors. Upon in situ thermal polymerization of l-ascorbic acid on the g-C3N4 surface, the carbon dots were homogeneously and solidly modified on the g-C3N4 surface. The CDs/g-C3N4 photocatalysts showed higher photocatalytic performance for H2 production than g-C3N4 under UV light irradiation using lactic acid as the sacrificial agent. The improved photocatalytic performance of CDs/g-C3N4 was mainly attributed to rapid interfacial charge transfer. After a Pt co-catalyst was loaded, the Pt-CDs/g-C3N4 catalyst formed exhibited a further improved photocatalytic performance for H2 production and could even split pure water to produce H2. Considering our present economic and facile synthetic approach for the modification of carbon dots on the surface of g-C3N4 photocatalysts, the as-prepared CDs/g-C3N4 photocatalysts will be promising for practical use in water splitting. [ABSTRACT FROM AUTHOR]

The construction of a Z-scheme heterojunction favors the improvement of the photocatalytic activity of photocatalysts. Herein, the LaVO 4 /Bi 3 O 4 Cl Z-scheme heterojunction was designed reasonably by the method of in situ growth. The obtained heterojunction was further used as a photocatalyst for the degradation of ofloxacin (OFX), an antibiotic, in wastewater. The degradation efficiency of OFX by the optimal sample (LBC-2) was 94.3 % and the values of k were about 114.7 and 2.4 times those of LaVO 4 and Bi 3 O 4 Cl, respectively. In addition, LBC-2 maintained high activity after 4 cycles. The significantly reduced recombination rate of carriers in LBC-2 was reflected by the results of the photoluminescence (PL), photocurrent (PC), and electrochemical impedance spectroscopy (EIS) studies. The degradation pathways of OFX were proposed accounting to the intermediates detected by liquid chromatography-mass spectroscopy (LC-MS). Toxicity estimations showed that the toxicity of some intermediates decreased. This work provides new insight into the development of Z-scheme photocatalysts for the removal of antibiotics as pollutants. • Novel Z-scheme LaVO 4 /Bi 3 O 4 Cl composite photocatalysts were synthesized. • LaVO 4 /Bi 3 O 4 Cl composites exhibited excellent activity for ofloxacin degradation. • The apparent rate constant for ofloxacin degradation was about 114.7 and 2.4 times as that of LaVO 4 and Bi 3 O 4 Cl. • Z-scheme heterojunction boosted the fast transfer of charge carriers. • The degradation pathway of ofloxacin was deduced. [ABSTRACT FROM AUTHOR]

• Novle La 2 Ti 2 O 7 /Bi 5 O 7 I composite photocatalysts were synthesized. • The photocatalyst exhibited much higher performance for CIP degradation under visible light. • The apparent rate constant for CIP degradation was 57.7 times and 12.3 times as that of La 2 Ti 2 O 7 and Bi 5 O 7 I. • The mechanism on the enhanced performance was discussed deeply. The La 2 Ti 2 O 7 /Bi 5 O 7 I (LB) composite photocatalyst was synthesized by an in-situ growth method. The microstructure, optical properties, and energy band structure of the prepared photocatalysts were studied by a series of characterization methods. The photocatalytic activity was studied by degrading ciprofloxacin (CIP) under visible light. The effects of hybrid ratio (La 2 Ti 2 O 7 /Bi 5 O 7 I) on photocatalytic activity were investigated. The results showed that the composite photocatalyst exhibited better photocatalytic activity than the corresponding single component (La 2 Ti 2 O 7 or Bi 5 O 7 I). Among them, the LB-2 composite photocatalyst showed the optimal photocatalytic efficiency (reaction rate constant of 0.09403 min−1), which was 57.7 times and 12.3 times as that of La 2 Ti 2 O 7 and Bi 5 O 7 I, respectively. The enhanced activity of the composite photocatalyst was mainly ascribed to the formed heterojunction between La 2 Ti 2 O 7 and Bi 5 O 7 I. Finally, according to the data analysis and energy band theory, the possible charge transfer mechanism of La 2 Ti 2 O 7 /Bi 5 O 7 I composite photocatalyst was proposed. The degradation mechanism of CIP was also proposed based on the intermediates detected by LC-MS. [ABSTRACT FROM AUTHOR]

Direct Z-scheme Bi 3 TaO 7 –CdS semiconductor materials were synthesized via hydrothermal method. The activity of the composites was investigated by the ciprofloxacin (CIP) degradation under visible light irradiation. Bi 3 TaO 7 –CdS composite catalysts all exhibited enhanced photocatalytic performances compared to both single photocatalysts (Bi 3 TaO 7 and CdS). The characteristics of the morphology and structure, the photoelectric properties and the composition of chemical elements of these samples have been studied extensively. Besides, capture experiments demonstrated that superoxide radical and hole worked together for the CIP degradation. The optimal catalyst exhibited stable CIP degradation activity in four cycles repeating experiments. Finally, a possible Z-scheme charge migration mechanism was proposed for the Bi 3 TaO 7 –CdS composite photocatalysts. Three possible pathways were proposed for the CIP degradation based on the detected intermediates by LC/MS. This work provided a feasible idea for the further research of Z-scheme photocatalysts for the emerging contaminants degradation. • CdS/bismuth tantalate composite photocatalysts were synthesized for the first time. • The charge transfer followed Z-scheme mechanism. • The photocatalyst exhibited enhanced performance for CIP degradation of ciprofloxacin compared to Bi 3 TaO 7 and CdS. • The mechanism for the enhanced activity was discussed deeply. • The degradation pathways were deduced based on the detected intermediates. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Ag 2 CrO 4 /N-GQDs@g-C 3 N 4 core-shell photocatalyst was fabricated for the first time. • The composite exhibited superior photocatalytic activity under full-spectrum light. • The g-C 3 N 4 shell can collect photoelectrons and inhibit the photocorrosion of Ag 2 CrO 4. • N-GQDs can promote charge transfer and the formation of Z-scheme mechanism. Abstract It is a challenge to develop highly efficient and stable photocatalysts to harvest solar spectrum as broad as possible. In this work, for the first time, a nitrogen-doped graphene quantum dots (N-GQDs) modified Ag 2 CrO 4 @g-C 3 N 4 core-shell structured composite was fabricated to achieve full-spectrum response from UV to near-infrared (NIR) region. In the Ag 2 CrO 4 /N-GQDs@g-C 3 N 4 composites, Ag 2 CrO 4 and g-C 3 N 4 can be excited by UV and visible light, and N-GQDs can absorb NIR light to emit visible light, which greatly enhances the utilization of solar light. Moreover, compared with the normal hybrid heterojunctions, the core-shell structure provides larger contact area between Ag 2 CrO 4 and g-C 3 N 4. The large contact area and highly conductive N-GQDs effectively promote the photoelectron transfer from Ag 2 CrO 4 to g-C 3 N 4 , which not only restrains the charge combination, but also greatly inhibits the photocorrosion of Ag 2 CrO 4. The cycle experimental results showed that the performance of AN@CN did not decrease even after eight cycles of usage, and the XRD and EIS results also confirmed the stable nature of AN@CN composites. As a result, the optimized composites exhibit excellent photocatalytic degradation of doxycycline under full-spectrum light, and the possible photocatalytic mechanism was proposed. This work provides guidance for the design of high efficient photocatalysts with full-spectrum response and excellent stability. [ABSTRACT FROM AUTHOR]

Organic pollutants that are difficult to degrade with potential biological toxicity are challenges in the environmental field. Magnetic raspberry microspheres of three transition metal (Fe, Co, Ni) nitrate sources were prepared by simple chemical route using zinc gluconate aqueous solution as precursor, the adsorption-catalytic efficiency of which was studied in detail. The effects of the types of transition metal sources, zinc sources, carbon sources and addition amount on the phase composition, structure and properties were investigated. The specific surface area of the products under the optimal conditions is 531, 687 and 592 m2/g, which are 28, 36 and 31 times higher than that of the products with glucose porous carbon alone. In addition, the products also show excellent photoelectric, paramagnetic properties and stability. Interestingly, the phase compositions are Fe/ZnO/ZnFe 2 O 4 , Co/ZnO and ZnO/Ni 3 ZnC 0.7 coated with carbon substrate, quite different when the same amount of Fe, Co and Ni nitrates introduced into hydrothermal system, demonstrating heterojunction/doping, doping and heterojunction effects, respectively. Within 40 min, the microspheres could rapidly remove 65.6 mg/g, 146.1 mg/g and 114.6 mg/g of Rhodamine B, respectively, higher than the adsorption of glucose carbon (18.8 mg/g), of which the adsorption processes were in accordance with Pseudo second kinetics and Langmuir monolayer adsorption. These findings not only provide a strategy for the construction of magnetic raspberry microspheres ZnO/C composites with transition metal nitrate salts, but also contribute to the analysis of adsorption-photocatalysis mechanism, which has practical application in the environmental field. [Display omitted] • Effect of Zn, Fe and Co sources on raspberry-like ZnO/C species were studied. • Proved to possess paramagnetism, high specific area and charge transfer capability. • Excellent adsorption-catalytic and regeneration effects compared with carbon spheres. • RhB removal capacity could reach 146.1 mg/g with the removal rate being 97.7%. [ABSTRACT FROM AUTHOR]

• Sparse or assembled Au nanocrystals are precisely modulated into COFs matrix. • Light absorption and charge transfer are enhanced in all Au/COFs composites. • Interfacial reaction kinetics are greatly favored in sparsely dispersed Au/COFs. • Boosted activity and selectivity are achieved in photo-oxidation/reduction cases. Plasmonic Au nanocrystals (NCs) are incorporated into covalent organic frameworks (COFs) with precisely modulated distributions to improve the efficiency of electron-hole separation and optimize the charge-carrier utilization. Specifically, through balancing the rate of dynamic covalent reactions and assembly of NCs, sparsely dispersed Au NCs (AuSP/COFs) or the close packed ones (AuCP/COFs) in COFs are fabricated, in which the contributions of electron acceptors/cocatalysts on the catalytic properties of Au/COFs composites are addressed by EPR, PL, and electrochemical measurements. Au3SP/COFs shows the best photocatalytic performances in photodegradation of RhB (remove >95 % in 120 min, k w =1.8 min−1 g−1) and dehalogenation of phenacyl bromide (conversion >99 %, selectivity of acetophenone ∼92.8 %) under visible light irradiation, which are associated with accelerated electron transfer, increased available Au/COFs Schottky junctions and boosted interfacial reaction kinetics. Overall, this work contributes to the fundamental understanding of the how spatial distributions of NCs in COFs affect the photocatalytic performances. [ABSTRACT FROM AUTHOR]

CuI/CuII enhanced NH2-UiO-66 (Zr) photocatalysts were developed for effectively oxidizing NO indoor gas (500 ppb) under visible-light irradiation through the ligand to linker metal charge transfer (LLMCT) pathway. • Ligand to linker metal charge transfer (LLMCT) pathway in (NH 2 -UiO-66(Zr). • Fast photogenerated electrons transferring from organic linkers to Cu species. • High carrier density value (24.4*1021 cm−3) and long photogenerated charge lifetime (78.2 ps). • Excellent photocatalytic oxidation of low-concentration (550 ppb) of NO indoor gas. MOFs-based photocatalysts always suffer from poor performance owing to its slow charge transfer. Herein, transient metal Cu (CuI/II) species were introduced to NH 2 -UiO-66(Zr) (Cu-NU0) via in-situ partial reduction of CuII ions to CuI. A ligand to linker metal charge transfer (LLMCT) pathway in MOFs was constructed for accelerating the photogenerated electrons transfer from organic linkers to Cu species, greatly enhanced increasing both the carrier density value and the separation efficiency of photogenerated carriers. A longer photogenerated charge lifetime (78.2 ps) was obtained and about 4 times higher than that of Cu-NU0. More photogenerated electrons in the Cu coordinated MOFs (Cu-NU7) were transferred to the outside surface of the MOFs, producing O 2 − for the photocatalytic oxidation of low-concentration (550 ppb) of NO indoor flow gas. An 88 % removal rate of NO under visible-light irradiation (λ > 420 nm) was obtained and well maintained up to 24 h with excellent durability. [ABSTRACT FROM AUTHOR]