Fabrication of MOF-derived tubular In2O3@SnIn4S8 hybrid: Heterojunction formation and promoted photocatalytic reduction of Cr(VI) under visible light

Study on the photo/electrochemical bi-functional properties of a coupling interface of Ru[dcbpy]32+-AMT/Au by SECM imaging-based joint analytical method

A photo/electrochemical coupling interface of Ru[dcbpy]32+-AMT/Au (AMT; 5-Amino-1,3,4-thiadiazole-2-thiol) was fabricated using a dehydration condensation sulfhydrating method. For the interface functional properties, a combined dual-signal recording (CDSR) method was applied to characterize the response characteristics, and a scanning electrochemical microscopy-electrochemiluminescence (SECM-ECL) imaging was developed to assess the interface distribution uniformity. The interface biosensing compatibility was validated by constructing a simple DNA sensor. The research results show that the interaction between the two functional parameters follows a synergistic effect mechanism in the coupling conditions and an interference effect mechanism in the detection condition. Under optimized conditions, the saturation dual-signal response values are 156.0 and 86.8 μA, respectively. The statistics and imaging comparison analysis validate good interface distribution uniformity and stability performance. The DNA sensor's dual-signal detection limits to the signal probe (SP) are ∼30 fM and 0.3 pM with linear ranges of 100.0 fM ∼ 1.0 nM and 1.0 pM ∼ 10.0 nM, respectively. The fabricated interface exhibits an effective bi-functional response performance compatible with biosensing. The proposed imaging method has a high technical fit for studying photo/electrochemical coupling interfaces and can also provide a reference for other similar coupling interface analyses.

Metal organic framework anchored onto biowaste mediated carbon material (rGO) for remediation of chromium (VI) by the photocatalytic process

Groundwater contaminated with hexavalent chromium Cr(VI) causes serious health concerns for the ecosystem. In this study, a hybrid amino functionalized MOF@rGO nanocatalyst was produced by utilization of a biowaste mediated carbon material (reduced graphene oxide; rGO) and its surface was modified by in situ synthesis of a nanocrystalline, mixed ligand octahedral MOF containing iron metal and NH2 functional groups and the prepared composite was investigated for Cr (VI) removal. The photocatalytic degradation of Cr(VI) in aqueous solutions was carried out under UV irradiation. Using a batch mode system, the effect of numerous control variables was examined, and the process design and optimization were carried out by response surface methodology (RSM). The photocatalyst, NH2-MIL(53)-Fe@rGO, was intended to be a stable and highly effective nanocatalyst throughout the recycling tests. XRD, SEM, EDS, FTIR examinations were exploited to discover more about surface carbon embedded with MOF. 2 g/L of NH2-MIL-53(Fe)/rGO was utilized in degrading 200 mg/L of Cr(VI) in just 100 min, implying the selective efficacy of such a MOF-rGO nanocatalyst. Moreover, the Eg determinations well agreed with the predicted range of 2.7 eV, confirming its possibility to be exploited underneath visible light, via the Tauc plot. Thus, MOF anchored onto biowaste derived rGO photo-catalyst was successfully implemented in chromium degradation.

A novel SnIn4S8/ZnFe2O4 S-scheme heterojunction with excellent magnetic properties and photocatalytic degradation activity for tetracycline

The development of efficient and economical photocatalysts is considered a promising strategy for pollution remediation. Magnetically separable SnIn4S8/ZnFe2O4 composites (SIS/ZFO) were prepared by combining SIS with ZFO. The composite with a 30% ZFO mass ratio (SIS/ZFO-30) was the most effective and achieved 60% removal of tetracycline (TC) in 120 min. It has a rate constant of 7.94 × 10-3 min-1, which is 6.3 and 27.2 times higher than those of pure SIS and pure ZFO, respectively. The improved photocatalytic performance can be attributed to the formation of S-scheme heterojunctions between SIS and ZFO, which results in the strong absorption of visible light, the enhanced separation of electron-hole pairs, and the higher redox ability of photoinduced charges. Additionally, SIS/ZFO composites have excellent magnetic properties and high stability, and the recovered samples still retained good photocatalytic degradation performances after four cycles of experiments. Thus, the coupling of SIS with ZFO provides a valuable strategy for enhancing photocatalytic potential and offers a promising pathway for water remediation.

Highly Efficient SnIn4S8@ZnO Z-Scheme Heterojunction Photocatalyst for Methylene Blue Photodegradation

Building heterojunctions is a promising strategy for the achievement of highly efficient photocatalysis. Herein, a novel SnIn4S8@ZnO Z-scheme heterostructure with a tight contact interface was successfully constructed using a convenient two-step hydrothermal approach. The phase composition, morphology, specific surface area, as well as photophysical characteristics of SnIn4S8@ZnO were investigated through a series of characterization methods, respectively. Methylene blue (MB) was chosen as the target contaminant for photocatalytic degradation. In addition, the degradation process was fitted with pseudo-first-order kinetics. The as-prepared SnIn4S8@ZnO heterojunctions displayed excellent photocatalytic activities toward MB degradation. The optimized sample (ZS800), in which the molar ratio of ZnO to SnIn4S8 was 800, displayed the highest photodegradation efficiency toward MB (91%) after 20 min. Furthermore, the apparent rate constant of MB photodegradation using ZS800 (0.121 min-1) was 2.2 times that using ZnO (0.054 min-1). The improvement in photocatalytic activity could be ascribed to the efficient spatial separation of photoinduced charge carriers through a Z-scheme heterojunction with an intimate contact interface. The results in this paper bring a novel insight into constructing excellent ZnO-based photocatalytic systems for wastewater purification.

PdPbAg alloy NPs immobilized on reduced graphene oxide/In2O3 composites as highly active electrocatalysts for direct ethylene glycol fuel cells

rGO-modified indium oxide (In2O3) anchored PdPbAg nanoalloy composites (PdPbAg@rGO/In2O3) were prepared by a facile hydrothermal, annealing and reduction method. Electrochemical tests showed that the as-prepared trimetallic catalyst exhibited excellent electrocatalytic activity and high resistance to CO poisoning compared with commercial Pd/C, mono-Pd and different bimetallic catalysts. Specifically, PdPbAg@rGO/In2O3 has the highest forward peak current density of 213.89 mA cm-2, which is 7.89 times that of Pd/C (27.07 mA cm-2). After 3600 s chronoamperometry (CA) test, the retained current density of PdPbAg@rGO/In2O3 reaches 78.15% of the initial value. Its excellent electrocatalytic oxidation performance is attributed to the support with large specific surface area and the strong synergistic effect of PdPbAg nanoalloys, which provide a large number of interfaces and achievable reactive sites. In addition, the introduction of rGO into the In2O3 matrix contributes to its excellent electron transfer and large specific surface area, which is beneficial to improving the catalytic ability of the catalyst. The study of this novel composite material provides a conceptual and applicable route for the development of advanced high electrochemical performance Pd-based electrocatalysts for direct ethylene glycol fuel cells.

Self-powered Aptasensors Made with the In2O3-In2S3-Ti3C2 Composite for Dual-mode Detection of Microcystin-LR

A dual-mode self-powered aptasensing platform of photoelectrochemical (PEC) and photofuel cell (PFC) was constructed for Microcystin-LR (MC-LR) detection. Specifically, the In₂O₃-In₂S₃-Ti₃C₂ (IO-IS-TC) composite was facilely assembled on the base of MOF-derived In₂O₃ hollow tubulars, and the integrated mechanism and photoconversion efficiency are proposed and discussed in detail. Herein, a promising dual-mode sensing platform was constructed using the IO-IS-TC composite as a photoanode matrix with higher output power and obvious photocurrent response. Moreover, the dual-mode sensing platform did not require external bias and the addition of sacrificial agents under visible light irradiation. The enhanced PEC properties can be attributed to the matched energy level of ternary components and the improved separation of photogenerated carriers. Moreover, aptamer-based recognition was adopted to catch MC-LR molecules, which realized the highly sensitive and selective detection. The PFC aptasensor was exhibited at 50-5 × 10⁵ pmol/L with a detection limit of 17.4 pmol/L, and the PEC aptasensor was realized from 0.5 to 4 × 10⁵ pmol/L with a detection limit of 0.169 pmol/L. The proposed aptasensing platform showed good specificity, reproducibility, and stability, which paved the way for the construction of a fast and ultrasensitive PEC sensing methodology for environmental analysis.

Removal of heavy metals from wastewaters with biochar pyrolyzed from MgAl-layered double hydroxide-coated rice husk: Mechanism and application

This study reports a MgAl-LDH rice husk biochar composite (MgAl-LDH@RHB) with a regular hydrotalcite structure synthesized by a simple hydrothermal method, which was then used to remove Cd(II) and Cu(II) from water. The influencing factors on the adsorption performance were determined through batch adsorption experiments, and the adsorption characteristics and cycling capacity were evaluated with eight models and adsorption-desorption experiments. The results showed that the adsorption of Cd(II) and Cu(II) by MgAl-LDH@RHB conformed to the Langmuir-Freundlich model and PSO kinetics model, indicating single-layer chemical adsorption. In addition, the experimental maximum adsorption capacities for Cd(II) and Cu(II) were 125.34 and 104.34 mg g^-1, respectively. The adsorption of Cd(II) and Cu(II) by MgAl-LDH@RHB was dominated by surface precipitation and ion exchange. The findings reveal the mechanism for the heavy metal removal by MgAl-LDH@RHB and provide a theoretical reference for agricultural waste disposal and water pollution control.

An Isopolymolybdate-Incorporated Metal-Organic Framework with Sulfite Oxidase-Mimicking Activity for Photocatalytic Oxidation of Sulfides Utilizing In Situ-Generated Singlet Oxygen

Developing new photocatalysts for sulfide oxidation utilizing in situ-generated 1O2 is very significant. Inspired by natural enzymatic processes, we synthesized a mimic sulfite oxidase (SO), {[Co(Mo4O13)(TPT)2]} (CoMo-TPT), by incorporating an isopolymolybdate anion [Mo4O13]2- into a 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT)-based metal-organic framework under mild hydrothermal conditions. In this structure, {Mo4O13} units with intrinsic SO-like catalytic sites are beneficial for the selective oxidation of sulfite and thioether. The ultraviolet-visible spectra of CoMo-TPT exhibited strong absorption from 250 to 650 nm and potential application in the utilization of solar energy. Mott-Schottky measurements indicated that CoMo-TPT is an n-type semiconductor with a LUMO value of -0.70 V (vs NHE) and a HOMO value of 1.39 V. The transient photocurrent responses with strong current density cycles with visible light indicated CoMo-TPT has a high photochemical activity. The lower resistance indicated that CoMo-TPT has a higher efficiency of photoinduced electron and hole separation. CoMo-TPT displayed a high efficiency of 99% and a selectivity of 97.3% in photocatalytic oxidation of sulfides by utilizing in situ-generated 1O2 through a tandem process of formation of H2O2 from O2 followed by catalyzed disproportionation of H2O2.