Interfacial Charge Separation Research Articles

Highly sensitive hybrid silicon carbonitride piezoresistive sensors enabled by coupling piezoelectric effect

Piezoresistive sensors with high working temperature and excellent sensitivity are highly desired for in-situ measuring pressure in various high temperature applications. Polymer-derived silicon carbonitrides (SiCNs) are a novel class of materials with excellent stability and piezoresistive performance at high temperature, yet challenging to build to meet the rapid growth of large-area electronics. This work demonstrates a thin and highly sensitive hybrid SiCN piezoresistive films enabled by coupling piezoelectric effect of Al-doped ZnO (AZO). The hybrid thin films with the optimal nano-domain phase of SiCN features ultrahigh gauge factors of 6518 to 31,195 upon various compressive stresses, which are significantly larger than those of single-layer SiCN and other existing piezoresistive materials. First-principles calculations reveal that the charges from AZO layer accumulate and move toward the carbon clusters in SiCN under compressive stress, resulting in greater tunneling currents between carbon clusters and more significant piezoresistive effect. Moreover, superior piezoresistive performance of the optimal hybrid system can be characterized by atomic-scale binding energy and band gap change, as formation of the hybrid structure facilitates interfacial charge separation and increases density of electron at conduction band. This work opens an avenue for improving sensitivity of piezoresistive sensors by effective coupling of piezoelectric materials.

Enhanced Photocatalytic Properties of All-Organic IDT-COOH/O-CN S-Scheme Heterojunctions Through π-π Interaction and Internal Electric Field.

Herein, we present a distinct methodology for the in situ electrostatic assembly method for synthesizing a conjugated (IDT-COOH)/oxygen-doped g-C3N4 (O-CN) S-scheme heterojunction. The electron delocalization effect due to π-π interactions between O-CN and self-assembled IDT-COOH favors interfacial charge separation. The self-assembled IDT-COOH/O-CN exhibits a broadened visible absorption to generate more charge carriers. The internal electric field between the IDT-COOH and the O-CN interface provides a directional charge-transfer channel to increase the utilization of photoinduced charge carriers. Moreover, the active species (•O2-, h+, and 1O2) produced by IDT-COOH/O-CN under visible light play important roles in photocatalytic disinfection. The optimum 40% IDT-COOH/O-CN can kill 7-log of methicillin-resistant Staphylococcus aureus (MRSA) cells in 2 h and remove 88% tetracycline (TC) in 5 h, while O-CN only inactivates 1-log of MRSA cells and degrades 40% TC. This work contributes to a promising method to fabricate all-organic g-C3N4-based S-scheme heterojunction photocatalysts with a wide range of optical responses and enhanced exciton dissociation.

Construction of NiS/MnCdS S-scheme heterojunction for efficient photocatalytic overall water splitting: Regulation of surface sulfur vacancy and energy band structure

The overall water splitting based on specific photocatalysts is one of the ultimate ways to solve the energy and environmental crisis facing humanity. Sulfide photocatalysts have greater potential in photocatalytic production of solar fuel. However, due to its easy photocorrosion phenomenon, it not effectively driving the water oxidation semi-reaction to produce oxygen, so how to use sulfide photocatalyst to decompose pure water to achieve stoichiometric reaction of H2/O2 production remains a quite challenging task. Herein, sulfur vacancies-rich MnCdS nanoparticles were modified with NiS nanosheets through the hydrothermal derivation method. Different concentration gradients of sulfur-vacancy in MnCdS nanoparticles (MnCdS-Vs-X) with tunable band structures were successful prepared by regulating the concentration of hydrazine hydrate, thus improves the efficiency of light energy utilization and charge separation and the existence of S defects was verified by transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR). The density function theory (DFT) calculation bears out that the draw into of S vacancy adjusted the band structure of MnCdS. Moreover, the successful construction of an S-scheme heterojunction between NiS and MnCdS-Vs-3 has been strongly demonstrated by in-situ XPS and UPS, which promoted interfacial charge separation and further improved the photocatalytic hydrogen evolution efficiency. The as-obtained S-scheme 20 %NiS/MnCdS-Vs-3 heterojunction exhibit excellent visible-light H2 production activity of 4099.55 μmol g−1h−1, 6.75 times higher than pure MnCdS. Most importantly, the excellent and stable photocatalytic overall water splitting activity of H2-509.70 μmol g-1h−1/O2-254.90 μmol g-1h−1 were obtained over 20 % NiS/MnCdS-Vs-3, which further demonstrates the application value of NiS/MnCdS-Vs-3 photocatalysts. This work proposes new ideas for the application of S-vacancies and S-scheme heterojunction in addressing the stability issues associated with sulfide-based photocatalysts in photocatalytic water splitting.

In situ irradiated XPS investigation on S-scheme TiO2/Bi2S3 photocatalyst with high interfacial charge separation for highly efficient photothermal catalytic CO2 reduction

The combination of S-scheme heterojunction and photothermal effect is a promising strategy to achieve efficient CO2 photoreduction into solar fuel due to the boosted charge carrier separation efficiency and faster surface reaction rate. Herein, unique photothermal-coupled TiO2/Bi2S3 S-scheme heterojunction nanofibers were fabricated and applied to a full-spectrum CO2 photoreduction system. Density functional theory calculation and experimental analyses have confirmed the generation of the internal electric field and the S-scheme electron transfer pathway, leading to a highly efficient charge carrier separation. Thanks to the excellent photothermal conversion capacity of Bi2S3, the photogenerated electron transfer rate, and surface reaction rate were further accelerated in hybrid photocatalysts. Under the synergistic effect of S-scheme heterojunction and photothermal effects, the optimal TiO2/Bi2S3 nanofibers achieved 7.65 μmol h–1 of CH4 production rate, which is 5.24 times higher than that of pristine TiO2. Moreover, the morphology reconstruction of Bi2S3 in hybrids facilitates the CH4 selectivity was significantly improved from 64.2% to 88.7%. Meanwhile, the CO2 photoreduction reaction route over TiO2/Bi2S3 nanofibers was investigated based on in-situ Fourier transform infrared spectra. This work provides some useful hints for designing highly efficient photothermal-coupled photocatalysts for CO2 photoreduction.

Dynamic in situ Formation of Cu2O Sub‐Nanoclusters through Photoinduced pseudo‐Fehling's Reaction for Selective and Efficient Nitrate‐to‐Ammonia Photosynthesis

AbstractCopper (Cu) is evidenced to be effective for constructing advanced catalysts. In particular, Cu2O is identified to be active for general catalytic reactions. However, conflicting results regarding the true structure‐activity correlations between Cu2O‐based active sites and efficiencies are usually reported. The structure of Cu2O undergoes dynamic evolution rather than remaining stable under working conditions, in which the actual reaction cannot proceed over the prefabricated Cu2O sites. Therefore, the dynamic construction of Cu2O active sites can be developed to promote catalytic efficiency and reveal the true structure‐activity correlations. Herein, by introducing the redox pairs of Cu2+ and reducing sugar into a photocatalysis system, it is clarified that the Cu2O sub‐nanoclusters (NCs), working as novel active sites, are on‐site constructed on the substrate via a photoinduced pseudo‐Fehling's route. The realistic interfacial charge separation and transformation capacities are remarkably promoted by the dynamic Cu2O NCs under the actual catalysis condition, which achieves a milestone efficiency for nitrate‐to‐ammonia photosynthesis, including the targets of production rate (1.98±0.04 mol gCu−1 h−1), conversion ratio (94.2±0.91 %), and selectivity (98.6 %±0.55 %). The current work develops an effective strategy for integrating the active site construction into realistic reactions, providing new opportunities for Cu‐based chemistry and catalysis sciences research.

Dynamic in situ Formation of Cu2 O Sub-Nanoclusters through Photoinduced pseudo-Fehling's Reaction for Selective and Efficient Nitrate-to-Ammonia Photosynthesis.

Copper (Cu) is evidenced to be effective for constructing advanced catalysts. In particular, Cu2 O is identified to be active for general catalytic reactions. However, conflicting results regarding the true structure-activity correlations between Cu2 O-based active sites and efficiencies are usually reported. The structure of Cu2 O undergoes dynamic evolution rather than remaining stable under working conditions, in which the actual reaction cannot proceed over the prefabricated Cu2 O sites. Therefore, the dynamic construction of Cu2 O active sites can be developed to promote catalytic efficiency and reveal the true structure-activity correlations. Herein, by introducing the redox pairs of Cu2+ and reducing sugar into a photocatalysis system, it is clarified that the Cu2 O sub-nanoclusters (NCs), working as novel active sites, are on-site constructed on the substrate via a photoinduced pseudo-Fehling's route. The realistic interfacial charge separation and transformation capacities are remarkably promoted by the dynamic Cu2 O NCs under the actual catalysis condition, which achieves a milestone efficiency for nitrate-to-ammonia photosynthesis, including the targets of production rate (1.98±0.04 mol gCu -1 h-1 ), conversion ratio (94.2±0.91 %), and selectivity (98.6 %±0.55 %). The current work develops an effective strategy for integrating the active site construction into realistic reactions, providing new opportunities for Cu-based chemistry and catalysis sciences research.

Facile green synthesis route for new ecofriendly photo catalyst for degradation acid red 8 dye and nitrogen recovery

This study novelty is that new photo catalyst prepared from sustainability low cost precursors. Dark red color hydrogel composites have been easily prepared from gelatin biopolymer using a simple sol–gel method. Gelatin doped by cobalt chloride, and silver nanoparticles (SNPs) in the presence of traces amount of sodium dodecyl sulfate surfactant and calcium chloride. Water-insoluble Gelatin composites are thermally stable photocatalysts for the degradation of toxic anionic acid red 8 dye. Promising photodynamic activity confirmed by fluorescence emission at λmax 650 nm. Optical absorption in Vis. light enhanced photo catalytic activity. Silver nanoparticles enhanced crystallinity, and improved optical properties and porosity. Dopants by CoCl2 and silver nanoparticles increased band gap of gelatin composites from (1.82 to 1.95) indicating interfacial charge separation. Low band gaps improved photo catalytic activity. Optical band gaps (Eg) lower than 2.0 eV indicates high catalytic activity in the photo degradation acid red 8 dye using Vis. light, wavelength 650 nm. Percent removal efficiency (%Re) of the dye at 500 ppm initial concentration, pH 1, contact time 30 min., and 0.20 g L−1 dose photo catalyst reached 95%. pH not affects removal efficiency. So, gelatin composites removed AR8 dye by photodegradation mechanism rather than adsorption due to photodynamic activity. Kinetics of photodegradation followed pseudo first order kinetic with rate constant k1 5.13 × 10−2 min.−1 Good electrical conductivity and magnetic properties (effective magnetic moment (µeff 4.11 B.M) improved dye degradation into simple inorganic species. Nutrients NH4+, and NO3− degradation products recovered by using alumina silicate clay via a cation exchange mechanism.

Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H2 Generation.

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti3C2) and semiconducting cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface of Ti3C2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H2 generation activity is found to be 12.23 and 16.26 mmol g-1 h-1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively, with good repeatability under visible-NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g-1 h-1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiOy formation, creation of proper dual p-n junction on a Ti3C2 sheet as supported by the Mott-Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti3C2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p-n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

Customizing precise, tunable, and universal cascade charge transfer chains towards versatile photoredox catalysis.

The core factors dictating the photocatalysis efficiency are predominantly centered on controllable modulation of anisotropic spatial charge transfer/separation and regulating vectorial charge transport pathways. Nonetheless, the sluggish charge transport kinetics and incapacity of precisely tuning interfacial charge flow at the nanoscale level are still the primary dilemma. Herein, we conceptually demonstrate the elaborate design of a cascade charge transport chain over transition metal chalcogenide-insulating polymer-cocatalyst (TIC) photosystems via a progressive self-assembly strategy. The intermediate ultrathin non-conjugated insulating polymer layer, i.e., poly(diallyl-dimethylammonium chloride) (PDDA), functions as the interfacial electron relay medium, and simultaneously, outermost co-catalysts serve as the terminal "electron reservoirs", synergistically contributing to the charge transport cascade pathway and substantially boosting the interfacial charge separation. We found that the insulating polymer mediated unidirectional charge transfer cascade is universal for a large variety of metal or non-metal reducing co-catalysts (Au, Ag, Pt, Ni, Co, Cu, NiSe2, CoSe2, and CuSe). More intriguingly, such peculiar charge flow characteristics endow the self-assembled TIC photosystems with versatile visible-light-driven photoredox catalysis towards photocatalytic hydrogen generation, anaerobic selective organic transformation, and CO2-to-fuel conversion. Our work would provide new inspiration for smartly mediating spatial vectorial charge transport towards emerging solar energy conversion.

Regulating the thickness of the NiO layer to optimize the photoinduced carrier separation behavior of BiVO4

The rational and effective regulation of interfacial charge separation and transport through the construction of composites is an effective strategy to improve photocatalytic performance.

Isotype heterojunction: tuning the heptazine/triazine phase of crystalline nitrogen-rich C3N5 towards multifunctional photocatalytic applications.

Photocatalytic technology has been well studied as a means to achieve sustainable energy generation through water splitting or chemical synthesis. Recently, a low C/N atomic ratio carbon nitride allotrope, C3N5, has been found to be highly prospective due to its excellent electronic properties and ample N-active sites compared to g-C3N4. Tangentially, crystalline g-C3N4 has also been a prospective candidate due to its improved electron transport and extended π-conjugated system. For the first time, our group successfully employed a one-step molten salt calcination method to prepare novel N-rich crystalline C3N5 and elucidate the effect of calcination temperature on the heptazine/triazine phase. Calcination temperatures of 500 °C (CC3N5-500) and 550 °C (CC3N5-550) lead to crystalline carbon nitride with both heptazine and triazine phases, forming an intimate isotype heterojunction for robust interfacial charge separation. An excellent photocatalytic hydrogen evolution rate (359.97 μmol h-1; apparent quantum efficiency (AQE): 12.86% at 420 nm) was achieved using CC3N5-500, which was 15-fold higher than that of pristine C3N5. Furthermore, CC3N5-500 exhibited improved activity for simultaneous benzyl alcohol oxidation and hydrogen production, as well as H2O2 production (AQE: 9.49% at 420 nm), signifying its multitudinous photoredox capabilities. Moreover, the recyclability tests of the optimal CC3N5-500 on a 3D-printed substrate also showed a 92% performance retention after 4 cycles (16 h). This highlights that crystalline C3N5 significantly augmented the reaction performance for diverse multifunctional solar-driven applications. As such, these results serve as a guide toward the structural tuning of 2D metal-free carbon nanomaterials with tunable crystallinity toward achieving boosted photocatalysis.

Atom-sharing Bi/Bi3O4Br plasmonic heterojunctions with effectively boosted photoelectrochemical activity for specific detection of chlorpyrifos

The increased environmental pollution caused by the overuse of the organophosphorus pesticide chlorpyrifos (CPF) has necessitated the development of an effective and selective photoelectrochemical (PEC) sensor. Herein, a Bi atom co-sharing Bi/Bi3O4Br plasmonic heterojunction was synthesized using an in-situ reduction process as a photoelectrode material to develop a highly selective PEC sensor for detecting CPF. Experimental characterizations and theoretical calculations demonstrate that the Bi atom-sharing heterostructure achieves tight contact in the heterointerface and effectively facilitates interfacial charge separation and migration. In addition, the deposition of Bi could greatly increase light-harvesting capacity of semiconductor materials resulting from the surface plasmon resonance (SPR) effect. Moreover, after the addition of CPF, the chelation between Bi3+ and C=N and P=S bonds in CPF hinders the mobility of photogenerated charges, leading to a decrease in the photocurrent signal intensity and selective determination of CPF. Compared to pristine Bi3O4Br, the proposed Bi/Bi3O4Br plasmonic heterojunction exhibits superior PEC activity. The developed PEC sensor showed a wide linear range (0.01–2000 ng/mL), a low detection limit of 0.0017 ng/mL (S/N=3), and superior selectivity and stability (RSD = 6.68%), which can be applied to CPF detection in tap water samples with recoveries of 97.2. to 102.9%. This study contributes to the rational design of a low-cost, highly efficient, and stable Bi-based plasmonic heterojunction for the CPF detection.

Induced S-scheme CoMn-LDH/C-MgO for advanced oxidation of amoxicillin under visible light

The development of low-cost photostable heterostructures with robust interfacial contact is critical for competent photoactivity and practical applications. The solid-state approach was successfully employed for fabrication of novel stacked oval-shaped CoMn-LDH/C-MgO composites with Mn-O-Mg bridges for efficient interfacial charge separation induced by S-scheme charge transfer for degradation of amoxicillin (AMX). The persulfate (PS) activation mechanism was confirmed by Raman analysis using bond length relationship to peak shifts. PS activation rate was 1.8 times of CoMn-LDH/PS for the S-scheme heterojunction with a 99.97 ± 0.16 % removal efficiency after 60 min of irradiation at pH 5.2. S-scheme photocatalytic ozonation increased AMX mineralization rate by up to 8 times compared to ozonation. Antimicrobial studies confirmed bacterial growth inhibition of composites and the by-products of AMX degradation had reduced bacterial growth inhibition compared to AMX. This work demonstrated the development of an S-scheme CoMn-LDH/C-MgO heterojunction as a visible light heterogeneous photocatalyst for degradation of pharmaceuticals.

Bilayered graded phase homojunction FA0.15MA0.85PbI3-based organic-inorganic hybrid perovskite solar cells crossing 22 % efficiency

Making highly efficient and stable perovskite solar cells (PSCs) are often based on the processing techniques, band gap of the material and effective interface charge separation. The efficiency of PSCs can be enhanced through several methods including the utilization of a solar-friendly absorber, interface passivation and the implementation of multi-junction spectrally matched absorbers or bilayered phase homojunction (BPHJ) consisting of identical absorbers. Here, we demonstrated BPHJ concept by stacking identical compositions of highly efficient and stable FA0.15MA0.85PbI3 perovskite absorbers adopting solution process (SP) and thermal evaporation (TEV) techniques. We successfully achieved FA0.15MA0.85PbI3 (SP)/FA0.15MA0.85PbI3-(TEV) based BPHJ normal n-i-p devices, which significantly crossing 22.% PCE. These improvement stems from effective deposition method for achieving high-quality FA0.15MA0.85PbI3-based BPHJ enabling smooth charge transfer at the interfaces. The resulting BPHJ-based champion device achieve a 22.13 % PCE and retain >95 % its original efficiency over 1000 hours.

Built-in electric field induced efficient interfacial charge separation via the intimate interface of CdS-based all-sulfide binary heterojunction for enhanced photoelectrochemical performance

Cadmium sulfide (CdS), as a prospective photoelectrochemical (PEC) photoanode material, has been restrained in hydrogen production owing to the severe recombination of charge carrier and the inherent photocorrosion. Herein, a thin shell consisted of cuprous sulfide (Cu2S) nanoparticles was formed on CdS nanorods arrays to overcome the shortages. An all-sulfide heterojunction not only establishes close interface and p-n junction between two semiconductors, but also possesses additional S atom channel for charge carrier migration, all beneficial for the efficient separation of photogenerated electrons/holes. In consequence, the transient photocurrent density of CdS/Cu2S reaches to 4.95 mA/cm2 under simulated sunlight with zero bias-potential, 1.4-fold of the pristine CdS. The excellent PEC performance results from the type-II band alignment and built-in electric field in heterojunction. Additionally, by the density functional theory, the calculated work function and band structure of CdS/Cu2S heterojunction gave strong evidences for the type-II charge transfer mechanism, and the established built-in electric field between p-n junction accelerated transfer and separation of photogenerated charge carriers.

Fast Interfacial Carrier Dynamics Modulated by Bidirectional Charge Transport Channels in ZnIn2 S4 -based Composite Photoanodes Probed by Scanning Photoelectrochemical Microscopy.

Limited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single-side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti2 C3 Tx MXene quantum dots (MQDs) and α-Fe2 O3 nanodots (FO) are anchored on the surface of ZnIn2 S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as "electron extractor" and S-O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high-performance composite electrodes.

Fast Interfacial Carrier Dynamics Modulated by Bidirectional Charge Transport Channels in ZnIn2S4‐based Composite Photoanodes Probed by Scanning Photoelectrochemical Microscopy

AbstractLimited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single‐side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti2C3Tx MXene quantum dots (MQDs) and α‐Fe2O3 nanodots (FO) are anchored on the surface of ZnIn2S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as “electron extractor” and S−O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high‐performance composite electrodes.

Visible-light photocatalytic degradation of two textile dyes by recyclable ZnO-Perlite: kinetic models and cost analysis

ABSTRACT Zinc oxide (ZnO), as an n-type semiconductor photocatalyst, is often selected due to its excellent photocatalytic performance and is supported on commercial expanded perlite (EP) to enhance interfacial charge separation efficiency under visible LED light. The structure and photocatalytic properties of the synthesised photocatalyst via the co-precipitation route were studied through XRD, FT-IR, SEM, EDX and pHpzc analyses. The photocatalytic response was evaluated by studying the degradation of two toxic and refractory azo dyes, reactive black 5 (RB5) and acid red 14 (AR14). Azo dyes (20 mg L−1) were completely degraded in the studied system, which occurred at pH 7 and 3, with catalyst amounts of 2 and 1 g L−1, and in the presence of H2O2 at 2 and 10 mM under LED light (15 W) within 2 h for RB5 and AR14, respectively. The degradation of RB5 and AR14 followed first-order kinetics with Kobs values of 0.0218 and 0.0169 min−1 and R2 values of 0.9271 and 0.8325, respectively. The assessment of energy consumption (EEO) and total operation cost (OC) confirmed that the supported ZnO offered the lowest power and cost requirements to transform selected pollutants into the acquired effluent, with values of 20.65 and 25.13 kWh m−3 and 3.11 and 3.205 USD kg−1 for RB5 and AR14, respectively, compared to using only VIS/ZnO, VIS/EP and VIS. Furthermore, the catalyst exhibited stability without the need for any additional chemicals for up to 10 h (5 reuse cycles). Additionally, the presence of major anions (sulphate, chloride and alkalinity) reduced the degradation efficiency in a real water matrix (1.74 and 1.47 times for RB5 and AR14, respectively) compared to that in distilled water.

S-scheme heterojunction and dual co-catalysts on carbonized paper for biphase interface photocatalytic hydrogen production from water

Solar-driven water splitting by photocatalysts is considered a cost-effective and environmental-friendly way to produce hydrogen fuel. However, the efficiency of hydrogen production in photocatalysis systems is still low due to the inefficient light absorption, photogenerated carrier recombination, and sluggish reaction kinetics. Here, we design and synthesize a composite carbonized paper with Co3O4/Fe2O3/g-C3N4/Au loaded on carbonized fiber (CF) by layer-by-layer assembly. Fe2O3 and g-C3N4 form an S-scheme heterojunction for enhanced interfacial charge separation. The spatially separated Co3O4 and Au co-catalysts capture photogenerated carriers and inhibit surface recombination for enhancing oxidation and reduction kinetics. In addition, composite carbonized paper floats on the water surface to form a solid-gas biphase photocatalytic interface (photothermal-generated steam/composite carbonized paper/hydrogen) with the help of the photothermal effect of composite carbonized paper. This biphase photocatalytic interface effectively reduces the transmission resistance of hydrogen and the adsorption barrier of water molecules. The CF/Co3O4/Fe2O3/g-C3N4/Au composite paper exhibits an impressive hydrogen production rate up to 78,561.51 μmol h−1 g−1. Stable loading of Co3O4/Fe2O3/g-C3N4/Au in composite paper contributes to the photocatalytic cycle. The hydrogen evolution rate in the third cycle remains 96.5 %. This work demonstrates that the combination of S-scheme heterojunction, spatially separated co-catalysts, and biphase photocatalytic interface can be a promising strategy for efficient photocatalytic platforms for solar hydrogen production.

Novel Z-scheme Nb2O5/C3N5 photocatalyst for boosted degradation of tetracycline antibiotics by visible light-assisted activation of persulfate system

Photocatalytic-assisted activation of persulfate (PDS) is regarded as a promising method for the rapid and efficient degradation of refractory pollutants in the water environment. In this study, a novel Nb2O5/C3N5 (NOCN) p-n heterojunctions composite was created by loading n-type Nb2O5 onto p-type C3N5 via an in-situ facile one-step calcination method. The NOCN/PDS system exhibited excellent performance in degrading tetracycline (TC) antibiotics under visible light and had great cyclic stability. The degradation efficiency of the coupled system reached 95 %, surpassing the pure C3N5 and PDS systems by 3.5 times and 2.4 times, respectively. The degradation rate of target pollutants was improved by the coupled system with the photocatalytic activation of PDS. The photogenerated electrons (e-) in NOCN were able to activate PDS effectively, which facilitated the creation of more reactive species. The Photoluminescence (PL) and other photoelectrochemical data demonstrated that the interfacial charge separation and photoresponsivity were remarkably enhanced in the coupled system. According to Mott-Schooky and electron spin resonance (ESR) characterization, it was confirmed that the reaction mechanism was the Z-scheme charge transfer mechanism based on p-n heterojunctions in the NOCN/PDS system. In addition, LC-MS analyses, TOC monitoring and biotoxicity analyses detected that the target pollutants were degraded to weakly bio-toxic micromolecules. In conclusion, this work provides valuable insights into the application of visible light-activated PDS technology in the degradation of organic pollutants, highlighting its potential for practical implementation.