The effective separation and transport of photoinduced electron–hole pairs in photoanodes is of great significance to photoelectrochemical and catalytic performance. Here, a facile and effective ...two-step strategy is developed to fabricate double-shelled ZnO/CdS/CdSe porous nanotube photoanodes from ZnO nanorod arrays (NRAs). Surprisingly, after the process of the deposition of CdS and CdSe, the ZnO nanorod arrays are partially dissolved, resulting in the formation of ZnO/CdS/CdSe porous nanotube arrays (NTAs). By virtue of their unique porous nanotube structure and cosensitization effect, the ZnO/CdS/CdSe porous NTAs show superior photoelectrochemical water-splitting performance and organic-pollutant-degradation ability under visible light irradiation, as well as excellent long-term photostability.
•The self-regulation of boron phases interface was realized during heat treatment.•A strong electronic interaction formed between amorphous phase and crystalline phase of modified boron.•The modified ...boron exhibited high sensitivity towards H2O2.•The modified boron showed excellent pollutant degradation efficiency in the EF sysytem.
The in-depth research on the interfacial interaction of crystal phases in metal-free catalysts during the 4 e− oxygen reduction reaction (ORR) are scarce. Herein, the modified amorphous boron (A-boron) with high electrochemical performance was fabricated with a simple high-temperature annealing process. The self-regulation of the crystal phases interface in modified A-boron (A-B-600N2) was realized through the designed synthesis process, which result in the formation of strong electronic interaction between the amorphous phase and crystalline phase. The increased oxygen adsorption and reduced internal resistance contribute to the improvement of electrochemical activity. In an alkaline solution, the A-B-600N2 exhibited as high as 85 mmol·gcatalyst−1·h−1 H2O2 production rate and 65% Faradaic efficiency (FE) value. Besides, A-B-600N2 also presented excellent activity for degrading a series of organic pollutants in the electro-Fenton (EF) system. This discovery provides a new idea for the modification of a boron-based electrocatalyst that is practicable for a high H2O2 production rate in the alkaline medium and excellent pollutant degradation efficiency in the EF system.
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Polymeric photocatalysts are promising candidates for water purification, however their catalytic performance are still unsatisfactory due to the fast charge recombination that leads to low reactive ...oxygen radicals production. In this study, a conceptual energy-transfer-mediated photocatalytic oxygen activation system over polymeric carbon nitride without the need of electron-hole separation is proposed, exhibiting remarkable singlet oxygen triggered bacteria inactivation performance as well as organic pollutants degradation. By structure and excitonic effect modulation, the oxygen activation process changes from the traditional electron-transfer mechanism to the final energy-transfer pathway, leading to the selective generation of singlet oxygen with high efficiency. The generated singlet oxygen is found to fervently attack the bacteria membrane, creating irreparable pores or holes on the cell membrane for cytoplasmic contents leaking out to accelerate bacteria destruction. The work demonstrated here offers a new photocatalytic oxygen activation pathway for achieving high-efficient reactive oxygen species generation performance without the need of charge separation.
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•A conceptual energy transfer mediated photocatalytic oxygen activation system is proposed.•Carbonyl groups modification enables the selective generation of singlet oxygen.•Enhanced photocatalytic radical generation without the need of electron-hole separation.•Enhanced singlet oxygen generation enables excellent water treatment performance.
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Herein, morphology control and element doping are adopted to overcome the shortcomings of insufficient contact with pollutants and limited light-harvesting capability of the pristine ...g-C3N4, and petal-like Cl-doped g-C3N4 nanosheets are fabricated by a flexible self-assembly route.
Efficient separation of photo-induced charge carriers is highly desired for improving photocatalytic activity. Herein, morphology control and element doping are adopted to overcome the shortcomings of insufficient contact with pollutants and limited light-harvesting capability of the pristine g-C3N4. Petal-like Cl-doped g-C3N4 nanosheets are fabricated by a flexible self-assembly route using melamine and cyanuric as precursors, with different amounts of NH4Cl added to adjust the chlorine doping ratio. Benefiting from the enlarged specific surface area (98.330 m2 g−1), tunable band structure and the effective charge separation, the prepared chlorine doping g-C3N4 nanosheets show obviously higher efficiency in the removal of rhodamine B (90 min, 94.3 %) and tetracycline hydrochloride (120 min, 65.7 %), with degradation kinetic rates about 15.8 and 2.3 times than that of pristine g-C3N4. The supramolecular self-assembly and chlorine doping display a noticeable synergy on enhancing the photocatalytic performance, enabled g-C3N4-based nano-sized photocatalysts to be highly competitive candidates for pollutant elimination.
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•Industrially applicable Ni-ZnS/g-C3N4 nanocomposites have been synthesized by the solid-state calcination method.•The photocatalytic activity for three different organic pollutants ...has been tested.•The synthesized nanocomposite material showed consistent photocatalytic activity for several cycles.•A possible photocatalytic mechanism is evidenced by quenching experiments.
In this paper, a series of nanocomposites consisting of different weight percentages of nickel-doped ZnS (Ni-ZnS)/graphitic-C3N4 (g-C3N4) have been synthesized via solid-state calcination of a mixture of pure g-C3N4 and 10 mol% Ni-ZnS. The proposed solid-state method is simple and provides a general route to make composite photocatalysts on a large scale. The shift in XRD peaks to lower theta value validates Ni+2 ion could be introduced effectually into the lattice of ZnS and substitutes to Zn+2 site. The interaction between Ni-ZnS and g-C3N4 in composite materials leads to long-lived charge carriers and efficient visible-light harvesting property. Which in turn showed remarkable high activity for degradation of RhB (92%, in 75 min), MB (96%, in 40 min) and paracetamol (86%, in 100 min), respectively. The photo mineralization of RhB, MB and paracetamol, over the most active 10 wt% Ni-ZnS/g-C3N4 nanocomposite was also evaluated by monitoring the reduction in TOC (total organic carbon) contents with respect to time under the visible light source. High-performance liquid chromatography results showed that no toxic by-products were formed during the photodegradation of paracetamol. On the basis of obtained results, a conceivable electron transfer mechanism has been stretched out for separating charge carriers and emphasizes the importance of superoxide and hydroxyl radicals for the degradation of pollutants in wastewater.
•Pharmaceutical sludge biochar (PSBC) was used to activate peroxymonosulfate (PMS).•PSBC/PMS removed 4-CP effectively with high rate constants of 0.42–1.70 min−1.•Rising pyrolysis temperature shifted ...reactive species from FeIVO2+ to SO4·−/·OH.•FeNx and FexN in PSBC were active sites of PMS to produce FeIVO2+ and SO4·−/·OH.
Pyrolysis of pharmaceutical sludge (PS) is a promising way of safe disposal and to recover energy and resources from waste. The resulting PS biochar (PSBC) is often used as adsorbent, but has seldom been explored as catalyst. Herein we demonstrate that PSBC (0.4 g/L) could efficiently activate peroxymonosulfate (PMS) to 100% degrade 4-chlorophenol (4-CP) with rate constants of 0.42–1.70 min−1, outperforming other reported catalysts. Interestingly, the PMS activation pathway highly depended on PSBC pyrolysis temperature, which produced dominantly high-valent iron species (e.g., FeIVO2+) at low temperature but more sulfate radical (SO4·−) and hydroxyl radical (·OH) at higher temperature, e.g., 0.17, 0.23, 0.12 mmol/L of FeIVO2+ and 0.009, 0.038, 0.102 mmol/L of SO4·−/·OH were produced within 10 min by PSBC-600/PMS, PSBC-800/PMS, and PSBC-1000/PMS, respectively. Characterization, density functional theory (DFT) simulation and Pearson correlation analysis revealed that along with the increase of pyrolysis temperatures, the active sites of PSBC gradually shifted from atomically dispersed N-coordinated Fe moieties (FeNx) to iron nitrides (FexN), which activated PMS to produce FeIVO2+ and SO4·−/·OH, respectively. This study clarifies the structure-activity relationships of PSBC for PMS activation, and opens a new avenue for the treatment and utilization of PS as high value-added resources.
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Bandgap engineering through single-atom site binding on semiconducting photocatalyst can boost the intrinsic activity, selectivity, carrier separation, and electron transport. Here, we report a ...mixed-valence Ag(0) and Ag(I) single atoms co-decorated semiconducting chalcopyrite quantum dots (Ag/CuFeS2 QDs) photocatalyst. It demonstrates efficient photocatalytic performances for specific organic dye (rhodamine B, denoted as RhB) as well as inorganic dye (Cr(VI)) removal in water under natural sunlight irradiation. The RhB degradation and Cr(VI) removal efficiencies by Ag/CuFeS2 QDs were 3.55 and 6.75 times higher than those of the naked CuFeS2 QDs at their optimal pH conditions, respectively. Besides, in a mixture of RhB and Cr(VI) solution under neutral condition, the removal ratio has been elevated from 30.2% to 79.4% for Cr(VI), and from 95.2% to 97.3% for RhB degradation by using Ag/CuFeS2 QDs after 2 h sunlight illumination. The intrinsic mechanism for the photocatalytic performance improvement is attributed to the narrow bandgap of the single-atomic Ag(I) anchored CuFeS2 QDs, which engineers the electronic structure as well as expands the optical light response range. Significantly, the highly active Ag(0)/CuFeS2 and Ag(I)/CuFeS2 effectively improve the separation efficiency of the carriers, thus enhancing the photocatalytic performances. This work presents a highly efficient single atom/QDs photocatalyst, constructed through bandgap engineering via mixed-valence single noble metal atoms binding on semiconducting QDs. It paves the way for developing high-efficiency single-atom photocatalysts for complex pollutions removal in dyeing wastewater environment.
A highly efficient photocatalyst is constructed through bandgap engineering via mixed-valence Ag single atoms decorated semiconducting chalcopyrite quantum dots (Ag/CuFeS2 QDs). It provides new insights into the design of high-efficiency single-atom photocatalysts for complex pollutions removal in wastewater. Display omitted
In this research work, the Sm3+ incorporated and rutile TiO2 nanorods coupled-GdFeO3 nanorods based nanocomposites are successfully prepared and gaged their visible-light photocatalytic activities ...for CO2 conversion and 2,4,6-trichlorophenol degradation. To this end, our investigation proved, that GdFeO3 and TiO2 nanorods have a wide surface area, high surface-to-volume values, and improved photocatalytic activities as compared to GdFeO3 and TiO2 nanoparticles respectively. Furthermore, the rutile TiO2 nanorods have significant performances as compared to anatase TiO2 nanorods. Based on our experimental and Ab initio approach, it is confirmed that the synergistic doping of Sm3+ interestingly elongated the visible light absorption proficiency via molding surface status and amending the band gap positions. Right after the coupling of rutile TiO2 nanorods performed the dual function of upgrading the charge separation by receiving HLEEs and activating the surface for CO2 adsorption via the photoelectron modulation approach. In contrast to pristine GdFeO3 nanorods, the optimal 4Sm-(GFONR) and 6RT/4Sm-(GFONR) samples showed efficient visible light activities for CO2 conversion and 2,4,6-trichlorophenol degradation. Fruitfully, our experiential investigations are consistent with the Ab initio and theoretical studies. Finally, our current novel findings will provide new feasible routes to synthesize morphology-based GdFeO3 photocatalysts for CO2 conversion and environmental remediation.
Synthesis scheme, schematic representation for energy bandgaps, photogenerated charge separation, and photocatalytic activities improvement mechanism over GFONR, 4Sm-(GFONR), and 6RT/4Sm-(GFONR) nanocomposite. Display omitted
•The Sm3+ incorporated and rutile TiO2 nanorods are coupled with GdFeO3 nanorods.•The synergistic doping of Sm3+ elongated the visible light absorption proficiency and amended the band gap positions.•The coupling of rutile TiO2 nanorods enhanced the charge separation and activated the surface for CO2 conversion.•The morphology manipulation, Sm3+ doping, and rutile TiO2 nanorods coupling improved the activities.•An agreeable experimental and computational approach is carried out.
Construction of a step-scheme (S-scheme) heterojunction photocatalyst is currently under investigation as it is known to facilitate a decrease in the e–/h+ recombination rate and preserves a strong ...redox ability. This research work has reported on the use of microwave irradiation combined with the wet impregnation synthesis of FeVO4/Bi4O5Br2 heterojunctions at different weight percentages (%wt) of FeVO4 (0.5%, 1%, 3% and 5%wt). The visible-light-driven photocatalytic activities for the photoreduction of Cr(VI), and the decontamination of certain organic pollutants (bisphenol A; BPA, rhodamine B; RhB, and tetracycline hydrochloride; TC) were also investigated. Ethylene glycol that was used as a reaction medium in the microwave synthesis process played a key role in the formation control of a flower-like structure of bismuth-rich Bi4O5Br2. Among the heterojunction photocatalysts, FeVO4/Bi4O5Br2 with 1%wt of FeVO4 markedly maximized the photocatalytic activity. Specifically, 95% of Cr(VI) was reduced by a reduction rate that was 6.0 times higher than that of Bi4O5Br2. Similarly, this photocatalyst was able to degrade 90%, 97%, and 88% of BPA, RhB, and TC at degradation rates that were 2.0, 1.2, and 1.6 times higher than Bi4O5Br2, respectively. Trapping experiments indicated that •O2− and h+ were the main active species responsible for the organic pollutant degradation, while •OH played a minor role in this process. These outcomes were confirmed with the use of the nitrotetrazolium blue transformation method and the terephthalic acid photoluminescence probing technique. Enhancement in the photo-activity of 1%wt-FeVO4/Bi4O5Br2 was attributed to the extended visible-light absorption range as well as the efficient generation, separation, and migration of photo-generated charge carriers through the S-scheme charge transfer mechanism which was supported by the results from the trapping experiments, XPS and UV–vis DRS analyses, Ag and PbO2 photo-deposition experiments, and electrochemical studies, along with the consideration of the reduction potentials of reactive oxygen species.
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•Novel FeVO4/Bi4O5Br2 catalyst for Cr(VI) reduction and organic pollutant degradation.•Ethylene glycol played a key role in the formation of flower-like Bi4O5Br2 structure.•Activity of Bi4O5Br2 promoted with optimum content of FeVO4 coupling (1%wt).•This FeVO4/Bi4O5Br2 nanocomposite displayed excellent recyclability and stability.•Improved activity was ascribed to S-scheme charge transfer mechanism.
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•Fenton fluidized bed (FFB) could remove As(III)/Fe(II) and organics simultaneously.•Slow As(III) but fast As(V) removal occurred on fluidizing iron-crystallized (IC) ...carriers.•Competitive complexion of As(V)/Fe(III) inhibited immobilizations on the IC carriers.•Recursive Fe(III) crystallization continuously provided essential surface OH groups for capturing As(V).•FFB showed effective As(V)/Fe(III) co-crystallization and COD removal in treating practical As(III) wastewater.
This study has demonstrated that the Fenton fluidized bed (FFB) technology could successfully immobilize As ions on the iron-crystallized (IC) carriers, with simultaneous crystallization of ferric and mineralization of organic pollutants. It was found that rapid fluidized immobilization of aqueous As(V) on the IC carriers was through surface favorable bidentate complexion, while the adsorptive removal of As(III) was rather slow. Adding Fe3+ caused competitive complexion and inhibited the As(V) immobilization. However, effective oxidative crystallization of Fe(II) and As(III) in FFB would take place. With the simultaneous generation of As(V) and Fe(III) by rapid •OH oxidation, two different crystalline precursors would be formed on the IC carriers, leading to efficient co-crystallization of As(V)/Fe(III). Recursive Fe(III) crystallization in the FFB continuously provided essential surface hydroxyl groups for capturing As(V), inducing layer-by-layer co-crystallized immobilization As(V)/Fe(III). The long-term continuous-flow treatment of a practical As(III)-containing industrial organic wastewater exhibited effective/stable co-crystallizations of As(V)/Fe(III), as well as COD removal. The FFB technology is expected to be a good option in treating complex industrial wastewater containing heavy metal and recalcitrant organic pollutants.
