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In recent years, many efforts have been devoted to boost molecular oxygen activation in semiconductor. This is because the reactive oxygen species (ROS) induced by molecular oxygen activation have been confirmed to play a great role in environmental remediation. Herein, we proposed a self-assembled plasmonic p-n heterojunction of WO3/Ag@Ag2O with enhanced molecular oxygen activation ability under visible and near-infrared (NIR) light irradiation. The prepared p-n heterojunction is favorable for the migration and separation of photo-generated hot charge carriers, which can promote the transformation of molecular oxygen to ROS with enhanced photocatalytic performance for norfloxacin (NOR) decomposition. The trapping experiments and Electron spin response (ESR) spectra demonstrate that both superoxide ( O2−) and singlet oxygen (1O2) are the main functional ROS for NOR degradation. The yield amount of O2− in the prepared hybrid catalyst is higher than that of pristine catalyst from nitrotetrazolium blue chloride (NBT) degradation. The sustainable generation of 1O2 is mainly ascribed to the charge transfer and energy transfer. Fluorescence spectra method is employed to confirm the generation of hydrogen peroxide (H2O2). The intermediates of NOR degradation are identified by LC/MS, and the possible degradation pathway is proposed in detail. A reasonable charge transfer pathway for the ultra-high hot charge carrier separation is studied. In addition, the as-prepared hybrid composite shows excellent photocatalytic performance for the degradation of rhodamine B (RhB) and ciprofloxacin (CIP). This study provides a promising avenue for fabrication of semiconductor with boosting molecular oxygen activation.

2,2′,4,4′-Tetrabrominateddiphenyl ether (BDE-47), as one of polybrominated diphenyl ethers (PBDEs), has been proven to be global contaminant owing to widespread utilization as flame retardant. Herein, a novel visible-light-driven (VLD) artificial indirect Z-scheme system of Ag@Ag3PO4/g-C3N4/rGO is finely designed for BDE-47 removal assisted with abundant solar energy. The novel hybrid composite exhibits an enhanced reductive debromination activity with removal efficiency of 93.4% under visible light irradiation (λ > 420 nm) for 120 min, which is 173.65 times higher than pristine g-C3N4 catalyst. A series of experiments in terms of the environmental effects of initial concentration, pH, solvent and light source are performed to optimize the photocatalytic performance. The presence of rGO as an excellent storing and shuttling medium, can further facilitate the charge carrier separation in the indirect Z-scheme system for the enhanced photo-reduction debromination performance. The accumulated electrons on the solid catalyst can attack the ortho-Br of BDE-47 to formation of BDE-28, and then so on. The protons (H+) can be reduced to atomic hydrogen (H°), which can greatly weaken para-Br of BDE-47 to generation of BDE-17. Furthermore, the remaining holes can react with CH3OH to generate CH2OH radical, and then further directly produce electron for debromination process. A possible debromination pathway for BDE-47 was proposed. This work provides a green and promising strategy utilizing solar energy to remove BDE-47 in the liquid medium by virtue of VLD composite.

Developing green and highly efficient water disinfection technique is of great importance to public health. Herein, a near-infrared (NIR) light-triggerable thermo-sensitive defective molybdenum oxide-nitrogen doped carbon (MoO3-x/NCNs) composite was fabricated and applied to water disinfection. With the synergy of photodynamic and photothermal effects, the MoO3-x/NCNs achieve a rapid and effective inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as compared to photocatalytic treatment or thermal catalytic alone. Particularly, MONC-3 with optimal ratio can completely inactivate 7.6 log of E. coli and S. aureus within 60 min and 100 min, respectively. The MONC-3 hybrid exhibits efficient charge separation and migration ability due to the formation of Schottky heterojunction, resulting in the highly enhanced O2− (11.34 × 10−10 M) generation activity. Meanwhile, excellent NIR light absorption and photothermal conversion efficiency (52.6%) of MONC-3 can generate local high temperature to promote photocatalytic reaction rate and destruct the bacterial integrity. The monitoring of cell damage process confirmed the irreversible death of bacteria. Based on density functional theory (DFT) calculation, the antibacterial mechanism and Schottky effect were clarified. This work provides new insights for constructing a water disinfection strategy based on plasma-induced photothermal synergy catalysis.

Interfacial engineering plays a critical role in modulating the electron transfer dynamics of photocatalysis, but has been rarely explored. Herein, a novel cobalt boride/graphitic carbon nitride nanosheet (CoB/CNs) Schottky junction with interfacial Co-N bond was successfully prepared to uncover the function of interfacial chemical bond in photocatalytic antibacterial process. Density functional theory (DFT) calculation and experimental investigation demonstrate that the interfacial Co-N bond can act as an electron transfer channel to efficiently steer the electron transfer from CNs to CoB, and then an upward band bending with the height of 0.26 eV is formed in CoB/CNs Schottky junction. The formed upward band bending can rapidly separate the photogenerated electron-hole pairs by preventing electrons from flowing back to the CNs, which causes the surface electron transfer efficiency (ηtrans) to increases from 41.8% (CNs) to 57.7% (CoB/CNs-2). Rotating disk electrode (RDE) results demonstrate that compared with CNs (n = 2.38), the oxygen reduction reaction in CoB/CNs-2 (n = 2.19) is more selective to a two-electron transfer route. Meanwhile, further research on reactive oxygen species reveals that it is an indirect two-step single-electron oxygen reduction process, which is beneficial for the generation of ·O2– and H2O2. As a result, 7 × 107 CFU/mL of Staphylococcus aureus (S. aureus) can be completely inactivated by CoB/CNs-2 with 125 min under visible light irradiation. It is expected that our work will provide some guidance for the exploitation of more advanced hybrid photocatalysts system through interfacial engineering.

High performance deep blue phosphorescent organic light-emitting diodes (PhOLEDs) were developed using a thermally activated delayed fluorescence type exciplex host. Three isomeric electron transport type host materials based on a triazine core, tetraphenylsilane and benzonitrile groups were synthesized for high triplet energy and good electron transport property in solid state. They formed thermally activated delayed fluorescence type exciplexes with a carbazole based hole transport type host. Among the three hosts, 3-(4,6-bis(3-(triphenylsilyl)phenyl)-1,3,5-triazin-2-yl)benzonitrile host achieved high external quantum efficiency of 21.0% and deep blue color coordinate of (0.14, 0.18). Moreover, the lifetime of the deep blue PhOLEDs was improved by more than 1.6 times using the new exciplex host compared with the state of the art mixed host.

A benzofuran based chemical platform, benzofurodibenzofuran, was designed and synthesized as a core structure to develop hosts for phosphorescent organic light-emitting diodes and thermally activated delayed fluorescence (TADF) emitters. The high triplet energy and rigid molecular structure of the benzofurodibenzofuran unit enabled the universal application of it as the building unit of the sky-blue hosts and emitters. The sky-blue TADF emitters built on the benzofurodibenzofuran platform showed high external quantum efficiency, narrow emission spectrum and blue-shifted emission color compared with the conventional phenyl based emitters. Moreover, the high triplet energy hosts obtained from benzofurodibenzofuran efficiently harvested the triplet excitons of the sky-blue phosphors and TADF emitters. Therefore, the benzofurodibenzofuran can work as the basic platform of designing host and emitters for high efficiency sky-blue organic light-emitting diodes.

Exciton effects play an important role in many polymeric photocatalytic systems, yet to date have largely been neglected in photocatalytic reactions over graphitic carbon nitride (g-CN). Since an exciton consists of a bound electron and hole, strategies that can boost the dissociation of exciton to generate a hot electron and hole should lead to enhanced photocatalytic activity. Herein, by using crystalline porous carbon nitride (CPCN) as a model, we demonstrate that grafting CPCN with electron accumulation capacity can efficiently facilitate the dissociation of exciton. Density functional theory (DFT) calculation shows that the introduced cyano group ( C N) in CPCN can distort the structure of carbon nitride and result in an energy disordered interface, thus, the electron in exciton can be extracted by C N and then stabilized by K+. Benefited from this electron accumulation process, the exciton in CPCN is effectively dissociated and the formed hot electron and hole is rapidly transferred. Specifically, the average lifespan (τave) is reduced from 3.76 ns (bulk carbon nitride, BCN) to 2.65 ns (CPCN), while the surface charge transfer efficiency (ηt) is increased from 36.6% (BCN) to 50.8% (CPCN). As a result, the obtained CPCN displays excellent performance for photocatalytic molecular oxygen activation. This work sheds light on the development of advanced carbon nitride-based photocatalysts for contaminant degradation and energy conversion through excitonic engineering.

The photocatalytic nitrogen reduction offers a promising strategy for ammonia (NH3) production, with the kinetics of the reaction depending on the transfer of photoinduced electrons to the adsorbed N2 molecules. However, the energetic electrons may flow into the defect states of the photocatalyst, thereby impeding nitrogen fixation. Herein, were report a novel heterojunction photocatalyst system for photocatalytic NH3 production, comprising BiO quantum dots (QDs) and nitrogen defective ultrathin carbon nitride (UCNx), which overcomes this limitation. Efficient spatial charge separation is achieved through nitrogen vacancies and the intimate heterojunction contact between the BiO QDs and UCNx. Benefitting from efficient charge separation, the adsorbed N2 on nitrogen vacancies and Bi2+ sites can effectively receive energetic electrons and in turn boost NH3 production. The optimal hybrid catalyst (BiCNx-5) shows excellent photocatalytic performance, with NH3 production rate of 576.11 μmol g−1 h−1 under visible light illumination (λ > 420 nm). This study provides a platform for the future design of effective photocatalysts for NH3 production.

In this study, the MnCo2O4/g-C3N4 (CMCN2) is used to activate peroxymonosulfate (PMS), for treating nitrobenzene (NB) and industrial wastewater containing nitrobenzene homologue. Different from traditional sulfate radical-based advanced oxidation processes (SR-AOPs), high-valent metal-oxo species (MIV(O)/MV(O)) is a major reactive component via dimethyl sulfoxide (DMSO) as a verify compound. The mechanism is speculated that the bond of nitrogen–metal = oxygen (N–M = O) activates PMS to form MIV(O)/MV(O) during sacrificial oxidation. The quenching experiments and electron spin resonance (ESR) confirm that CMCN2 activated PMS to form OH and SO4 –. The Langmuir-Hinshelwood model conforms to the NB degradation curve, and the best removal efficiency is 96.7% in 240 min. The CMCN2/PMS system has excellent stability between pH 3–10. Also, the CMCN2/PMS system exhibited satisfactory removal of NB in the presence of inorganic anions and natural organic matters. The treatment effect of industrial wastewater containing phenyl homologues shows that CMCN2/PMS has a high mineralization capacity. This study details the electron transfer during the formation of active components and provides new ideas for selecting active ingredients that degrade phenyl pollutants in the field of advanced oxidation.

In this work, electron-withdrawing groups functionalized few layer graphitic carbon nitride (FCN-12) nanosheet was prepared and utilized for photocatalytic activation of peroxymonosulfate (PMS). Experimental characterization and density functional theory (DFT) calculation reveals that the electronic structure of FCN-12 is efficiently adjusted by forming an upward band bending, as the functionalized carbonyl (C=O) and carboxyl (-COOH) groups can withdraw the electron from the C-N=C skeleton. With the addition of PMS, FCN-12 displays superb photocatalytic activity for chlortetracycline hydrochloride (CTC) degradation, where 83.4% CTC can be degraded within 120 min under visible light irradiation, much higher than that of bulk g-C3N4 (34.3%). Besides, even under the different pH condition and co-existed anions environment, FCN-12/PMS/vis system still exhibits favorable applicability. The boosted catalytic performance is resulted from the collective effect of the few-layer feature and the energy band bending, which leads to the effective migration of photogenerated electron from FCN-12 to PMS via C=O and -COOH groups. This work not only provides an exhaustive insight into the role of energy band bending in electron-withdrawing group functionalized g-C3N4, but also paves the avenue for the development of metal-free photocatalyst-mediated environmental remediation based on PMS activation.

A hollow tubular graphitic carbon nitride (g-C3N4) with nitrogen vacancy was successfully prepared via simple hydrothermal calcination method. The hollow tubular structure has the functions of increasing the specific surface area, promoting the multiple scattering effect of light, as well as imparting the directional transfer of electrons. Simultaneously, the introduction of vacancy defect can manipulate the electronic structure of g-C3N4 with narrow band-gap and excellent charge carrier behavior. The catalytic activity of the photocatalysts were evaluated by the degradation reaction of chlortetracycline hydrochloride (CTC·HCl) and hydrogen evolution reaction (HER). The results indicated that the photocatalytic property of the resulting g-C3N4 tube with appropriate nitrogen vacancy was significantly better than that of original g-C3N4. Under visible light irradiation, ND-TCN-10 demonstrated the optimal photocatalytic degradation effect and achieved a hydrogen generation rate of 235.68 μmol g−1 h−1. In addition, based on the liquid chromatography-mass spectrometry (LC-MS), the main by-products of CTC·HCl and the possible degradation pathways were analyzed. The method of introducing nitrogen deficiency into the tubular structure provides a promising strategy for increasing the photocatalytic activity of g-C3N4-based materials.

Designing efficient semiconductors for photocatalytic nitrogen reduction reaction (N2RR) is an urgent challenge for artificial ammonia (NH3) production under ambient condition. Graphitic carbon nitride (GCN) shows fascinating potential in conversion of inert chemical bonds into high-value-added products. However, the low NH3 conversion efficiency in GCN leads to unsatisfied practical application. Herein, a defect-dopant strategy through introduction of nitrogen defects and boron (B) heteroatoms is proposed to boost NH3 production. The optimal catalyst shows enhanced photocatalytic activity with NH3 conversion rate of 435.28 μmol g−1 h−1 under visible light illumination. The boosting NH3 production is owing to the synergistic effect of nitrogen defect and B dopant. The nitrogen defect is favorable for promoting the optical harvesting ability, charge carrier separation efficiency as well as N2 adsorption ability. B dopant not only enhances N2 adsorption and activation ability, but also maintains the high reduction ability of BNUCNx. Density functional theory (DFT) calculation shows that high adsorption energy for N2 and longer N–N bond length of N2 are simultaneously obtained in BNUCNx, contributing to NH3 production. Furthermore, the high molecular oxygen activation ability in BNUCNx shows great potential for environmental remediation. This work provides a pioneering perspective for enhancing photocatalytic N2RR through defect-dopant strategy.

Light-driven reactive oxygen species (ROS) generation from molecular oxygen activation is normally recognized as an effective route for environmental pollutants removal. Herein, oxygen-substituted ultrathin porous graphitic carbon nitride (g-C3N4) nanosheets are prepared through a two-step hydrothermal-recalcination treatment of bulk g-C3N4 (BCN), and it is found that the obtained samples display enhanced ROS generation, as reflected by the removal of oxytetracycline hydrochloride (OTC). When stimulated by visible light, about 85.76% of OTC can be removed by the optimal sample (OCN-24-550) within 120 min, which is obviously higher than that of bulk g-C3N4 by a factor of 4.99. Meanwhile, nitroblue tetrazolium (NBT) transformation and H2O2 generation also indicate that the OCN-24-550 possess the highest reactivity, which can produce 47.25 μM of H2O2 and 9.07 × 10−10 M of the steady-state O2− during the reaction. The enhanced photocatalytic performance of OCN-24-550 is attributed to the synergistic effect of ultrathin porous structure and heteroatom O substitution. Specifically, the ultrathin porous structure can enlarge the surface area and then facilitate the diffusion of reactant, while the O substitution can optimize the electronic structure by creating a local electronic polarization effect, as confirmed by density functional theory (DFT) calculations, and thus result in a boosted exciton dissociation and accelerated charge migration. This work not only presents a comprehensive insight into g-C3N4-based reaction system from exciton and charge carrier, but also provides a meaningful guidance for exploring novel photocatalytic wastewater treatment devices from a more environment-friendly perspective.

A highly efficient and easily recoverable catalyst is always desirable for practical photocatalytic applications. In this study, a magnetically separable ZnFe2O4/NCDs/Ag2CO3 Z-scheme heterojunction photocatalyst using nitrogen doped carbon quantum dots (NCDs) as solid-state electron mediators was fabricated by an easy-operated deposition-precipitation method. The prepared ZnFe2O4/NCDs/Ag2CO3 photocatalyst exhibits a promoted photocatalytic activity for Levofloxacin (LVFX) removal compared to single ZnFe2O4 and Ag2CO3, achieving 88.75% and 22.53% degradation efficiency under visible and near-infrared (NIR) light irradiation, respectively. Characterization results show that the synergistic effect of remarkable charge carrier separation efficiency and broadened solar light absorption is responsible for the enhanced photocatalytic performance. The well-matched band structures of the two semiconductors facilitate the charge transfer in Z-scheme transfer model, resulting in high charge separation rate. Simultaneously, due to the superb electron transfer character of NCDs, the introduction of NCDs can further accelerate the transfer of the photo-generated charges as solid-state electron mediators between ZnFe2O4 and Ag2CO3. Furthermore, the unique up-converted photoluminescence properties of NCDs can broaden the optical absorption of the prepared ZnFe2O4/NCDs/Ag2CO3 to NIR region, thus leading to an enhanced utilization of solar energy. This work provides a novel insight into the fabrication of novel all-solid-state Z-scheme photocatalyst based on nitrogen doped carbon quantum dots and opens new vista for the design of magnetically separable and highly efficient photocatalysts for environmental remediation.

Reactive oxygen species (ROS), which are generated from molecular oxygen activation and oxidization of H2O/OH− in photocatalysis process, are vital for environmental remediation. In this study, a dual strategy for boosting ROS generation is proposed by construction of ultrathin Z-scheme heterojunction of Bi5O7I/g-C3N4. The charge-carrier-quenching effect is inhibited attributed to the prepared ultrathin 2D/2D heterojunction. Profiting from the interfacial charge properties, the boosting molecular oxygen activation and oxidization ability are obtained in the heterojunction. In comparison with pristine catalysts, the yield amount of superoxide ( O2−) in Bi5O7I/g-C3N4 case shows enhancement. Furthermore, controllable experiments demonstrate that the generation of hydrogen peroxide (H2O2) is through two-step electron reduction strategy, and it can decompose into hydroxyl radicals ( OH) assisted with photoelectrons. The singlet oxygen (1O2) is produced by two transfer pathways including charge transfer and energy transfer. Through DFT calculation, the built-in electronic field (IEF) is formed owing to the electron configuration. The IEF in the heterojunction tunes the charge transfer from type-II to Z-scheme model. Simultaneously, the short charge transfer distance enables more high energy charge carriers to reach the surface of solid catalyst for catalytic reactions. Owing to the boosting ROS generation, the novel composite shows enhanced photocatalytic performance for ciprofloxacin (CIP) degradation. This study gives a proof-of-concept perspective on fabrication of 2D/2D Z-scheme heterojunction with boosting ROS generation for environmental remediation and energy conversion.

Antibiotics existing in wastewaters must be degraded to eliminate its antibacterial activity before discharging into the environment. Electrochemical reduction by continuous electrons supply can degrade various refractory pollutants, however, the information about the feasibility and characterization of the cathodic degradation of nitrofurans antibiotic furazolidone (FZD) is scarce. Here, we investigated the degradation of FZD using a poised cathode electrochemical reactor. The cyclic voltammetry (CV) preliminarily proved the feasibility of FZD degradation on cathode. In contrast to the different buffer solutions concentrations, buffer types, and initial FZD concentrations which only had obvious impact on the FZD degradation efficiency, different cathode potentials had significant effects both on the FZD degradation efficiency and degradation products composition. Catholyte PBS could be replaced by Na2CO3–NaHCO3 and NaCl buffer solution for the FZD degradation. The cathodic degradation pathway of FZD was proposed based on intermediate products analysis. When the cathode potential was lower than −0.75 V, both the furan ring and oxazole ring of FZD were destroyed to generate linear chain products after N–N bond disconnection, suggesting that the high toxic biological metabolite of FZD, 3-amino-2-oxazolidinone (AOZ) could be detoxified by cathodic degradation. This study suggests that the electrochemical reduction could serve as a potential strategy for the treatment of FZD and AOZ containing wastewater.