Construction of 2D/2D MoS2/g-C3N4 Heterostructures for Photoreduction of Cr (VI)

Highly Active MXene Quantum Dots/CuSe n-p Plasmonic Heterostructures for Ultrafast Photocatalytic Removal of Cr(VI) under Full Solar Spectrum

Identifying effective plasmonic photocatalysts exhibiting robust activities across the entire solar spectrum poses a significant challenge. CuSe, with its local surface plasmon resonance (LSPR) effect, has garnered attention as a prospective plasmonic photocatalyst. However, severe charge recombination and insufficient light absorption limit its photocatalytic performance. To enhance the performance, constructing CuSe-based n-p plasmonic semiconductor heterostructures is a potential strategy. MXene quantum dots (MQDs), a kind of n-type plasmonic semiconductor with metallic conductivity and a high LSPR effect, are a promising candidate to couple with p-type CuSe. According to the complementary principle, we designed a 0D/2D MQDs/CuSe n-p plasmonic semiconductor, achieved by wrapping CuSe nanosheets with MQDs. This n-p plasmonic heterostructure exhibits a synergistic effect on an enhanced electronic field, facilitating charge transfer and separation, thereby enhancing charge excitation, carrier migration, and photothermal effect. Furthermore, optimizing the MQD loading content leads to an ultrafast photocatalytic reaction rate, achieving 100% Cr(VI) reduction efficiency within just 60 min with a reaction kinetics of 0.069 min-1, surpassing the performance of bare CuSe. Our work presents a promising approach for developing advanced n-p plasmonic heterostructures based on MQDs for wastewater treatment and other photocatalytic applications.

A timely update on g-C3N4-based photocatalysts towards the remediation of Cr(vi) in aqueous streams

Hexavalent chromium (Cr(vi)) is a prominent carcinogen. In environmental engineering, the elimination of hexavalent chromium from aqueous media is a noteworthy field of study. In this regard, nanoparticle science and technology have contributed significantly to the photocatalytic reduction of Cr(vi). In this review, a methodical search was undertaken to discover the most recent advancements in the field of photocatalytic reduction of Cr(vi) utilizing g-C3N4 and composites derived from it. This paper deals with the advancements and applications of g-C3N4 and its composites in the Cr(vi) remediation of water-borne pollutants. Different intriguing systems, suggested by various researcher groups, have been discussed. Different characterization techniques often conducted on photocatalysts based on g-C3N4 have also been highlighted so as to gain an understanding of the Cr(vi) removal process. Lastly, the future scope of the g-C3N4-derived photocatalysts, present challenges, and the viability of employing these photocatalysts in an extensive treatment plant have been discussed.

Urea-driven g-C3N4 nanostructures for highly efficient photoreduction of Cr(vi) under visible LED light: effects of calcination temperature

Graphitic carbon nitride (g-C3N4) nanostructures were synthesized via the calcination of urea at various temperatures ranging between 400 and 600 °C and were utilized for photoreduction of Cr(vi) in aqueous medium. Due to the low adsorption of Cr(vi) on the g-C3N4 surface, a more accurate assessment of the photocatalytic performance of the samples was carried out. Although the characterization showed that the specific surface of samples increased as the calcination temperature increased, the most efficient product in terms of the photoreduction duration of Cr(vi) was produced through the calcination process carried out at 450 °C, which reduced the concentration by more than 99% in 40 minutes. These results demonstrate that the structural and surface properties of g-C3N4 are critical factors that impact the photocatalytic performance. Alongside the calcination temperatures, the concentration of citric acid as a hole scavenger, the source of illumination, pH levels, and the recycling ability of the produced specimen at 450 °C were also investigated. Conspicuously, the photocatalyst works better when more citric acid is present and the pH level decreases. Out of all the cases studied regarding the light source, the 400 nm LED light source was found to be the most efficient. Additionally, even after going through the photoreduction process four times, the photocatalyst still remained highly efficient.

A 3D hierarchical TiO2/CaIn2S4/C3N4arrays photoanode with dual-heterojunction for enhanced photoelectrochemical performance

A novel 3D hierarchical TiO2/CaIn2S4/C3N4arrays with dual heterojunctions photoanode is constructed by stepwise deposition of CaIn2S4nanosheets and ultrathin C3N4onto the well-aligned TiO2nanorods arrays. Integrating the merit of the superior ability of CaIn2S4and C3N4to harvest visible light, dual type-Ⅱ heterojunction band structure and one-dimensional ordered nanostructures, the TiO2/CaIn2S4/C3N4photoanode exhibits simultaneous significant improvements in visible-light harvesting, charge separation and electron transfer capability. At 1.23 V (versus reversible hydrogen electrode) under AM 1.5 G irradiation, the TiO2/CaIn2S475/C3N4photoanode exhibits a photocurrent density of 4.5 mA cm-2, which is 5.2 and 51.1-fold higher than that of TiO2/CaIn2S475 and pristine TiO2photoanode, respectively. Moreover, the applied bias photo-to-current efficiency (ABPE) of the TiO2/CaIn2S475/C3N4photoanode reaches 3.5% at 0.36 V (versus reversible hydrogen electrode). These results are helpful for fabricating more efficient heterostructure photoelectrodes.

Photodegradation of rhodamine-B in aqueous environment using visible-active gC3N4@CS-MoS2 nanocomposite

Rapid industrial expansion leads to environmental pollution especially in an aqueous environment. Photocatalytic degradation is one of the most efficient and environmentally friendly techniques used to treat industrial pollution due to its complete degradation capability of a variety of water contaminants to their non-toxic state. Graphitic carbon nitride (gC3N4) and molybdenum disulfide (MoS2) provide efficient dye degradation, but MoS2 has few disadvantages. Hence, chitosan (CS) supported gC3N4-MoS2 hybrid nanocomposite was developed in this study to reduce these issues by accelerating the degradation of dye molecules such as rhodamine-B under visible light. The prepared gC3N4@CS-MoS2 hybrid nanocomposite was thoroughly characterized using various analytical tools including FTIR, XRD, SEM, EDX, XPS, UV-Visible, and PL spectra. Several influencing parameters such as irradiation time, initial pH, dosage, and initial dye concentration were optimized by batch mode. The photodegradation of rhodamine-B could be induced by the heterogeneous gC3N4@CS-MoS2-water hybrid nanocomposite. The narrow band gap of gC3N4@CS-MoS2 (1.80 eV) makes it suitable for effective degradation of rhodamine-B due to more active in the visible region and attained its highest degradation efficiency of 99% after 40 min at pH 8 with minimum dosage of 60 mg. The possible degradation mechanism was tentatively proposed for rhodamine-B dye molecules from aqueous environment. The present work shows a novel photocatalyst for the purification and detoxification of dye molecules as well as other water contaminants found in polluted wastewater.

Synergistic Generation of Radicals by Formic Acid/H2O2/g-C3N4 Nanosheets for Ultra-efficient Oxidative Photodegradation of Rhodamine B

Water pollution is a global challenge endangering people's health. In this work, an ultra-efficient photodegradation system of Rhodamine B (RhB) has been established using a graphitic carbon nitride nanosheet (CNNS) as the semiconductor photocatalyst, from which energy is harvested on both the conduction band and valence band by formic acid and hydrogen peroxide, respectively. The optimized FA/H₂O₂/CNNS system increases the apparent photodegradation rate of RhB by 25 folds, from 0.0198 to 0.4975 min^-1. Through a comprehensive investigation with reactive oxygen species scavengers, electron paramagnetic resonance, high-performance liquid chromatography-mass spectrometry, etc., an oxidative mechanism for RhB photodegradation has been proposed, which combines enhanced charge carrier migration and synergistic generation of multiple radicals. Comparable performance improvements have also been observed for similar systems with different semiconductors, suggesting that such a catalytic system could afford a general approach to enhance semiconductor-catalyzed photodegradation.

Two polymolybdate-directed Zn(ii) complexes tuned by a new bis-pyridine-bis-amide ligand with a diphenylketone spacer for efficient ampere sensing and dye adsorption

Two polymolybdate-based Zn(ii) complexes were constructed from a new bis-pyridine-bis-amide ligand, which can be used as electrocatalysts and electrochemical sensors for Cr(vi), KBrO3, H2O2 and AA, and exhibit selective adsorption of CV and MB.

Insight into the synergistic adsorption-reduction character of chromium(VI) onto poly(pyrogallol-tetraethylene pentamine) microsphere in synthetic wastewater

Facile fabrication of the ultra-high-performance adsorbent can effectively ameliorate the Cr(VI)-pollution elimination in sewage control. Herein, a simple synthesis strategy is proposed to tap a versatile chelating resin poly(pyrogallol-tetraethylene pentamine) (PPTA) with respect to Cr(VI) removal from solution. Multiple changing factors which affect the adsorption behavior of PPTA are explored sequentially, such as initial pH, adsorbate concentration, adsorbent dosage, temperature, foreign ions, etc. The microstructure and functional mechanism of synthetic adsorbent are investigated systematically by means of various characterizations including TEM, EDS, FT-IR, XPS, etc. Consequently, the as-prepared PPTA-3 microsphere by reactant ratio of 1: 1 represents a brilliant synergistic adsorption and reduction result for Cr(VI) by the drastic electrostatic interaction of -NH₃⁺ and -OH₂⁺ groups, including satisfactory removal efficiency which closes to 100 % in low concentration, favorable specificity for the influence from coexistent ions (Mo(VI), Mn(VII), Cl^-, Cr(III), etc), and passable recyclability. Following the surpassingly fitting with Langmuir isotherm model, its maximum capacity reaches 714.29 mg g^-1 at 30 °C. The removal performance is essentially in agreement with the pseudo-second-order kinetics, simultaneously, suffers the rate-limiting impact depending on intra-particle diffusion process. In brief, this newly developed chelating resin presents an effective means with regard to the Cr(VI)-wastewater treatment or other uses in the future.