Reactive Surface Sites Research Articles

A review of photoelectrochemical water oxidation using hematite photoanode

Background: The sun, as an abundant and renewable energy source, provides a sustainable alternative to fossil fuels, which contribute significantly to CO₂ emissions and global warming. With CO₂ emissions surpassing 35 billion tons in 2023, the need for clean energy solutions has become increasingly urgent. Solar energy utilization includes photoelectrochemical (PEC) water splitting, where hematite is widely recognized as an efficient photoanode material due to its availability, stability, and favorable band gap for visible light absorption. However, hematite faces challenges such as poor conductivity, surface recombination, and slow oxygen evolution reaction (OER) kinetics, which limit its performance. Methods: This review examines various strategies to enhance hematite photoanode performance for PEC water splitting. The study explores three key approaches: (1) using three-dimensional conductive substrates with high surface area to facilitate heterojunction formation, (2) doping with tetravalent metal ions (e.g., Ti⁴⁺) to improve conductivity and charge carrier density, and (3) integrating Bi₂WO₆ with hematite to enhance charge separation and photoelectrochemical efficiency. The hydrothermal method was applied for hematite fabrication due to its feasibility, cost-effectiveness, and scalability. Findings: The analysis highlights the effectiveness of each strategy in overcoming hematite’s inherent limitations. The use of 3D conductive substrates improves electron transport and surface reaction sites, while Ti⁴⁺ doping enhances charge carrier density and conductivity. Conclusion: Hematite remains a promising photoanode material for PEC water splitting, but its limitations must be addressed to maximize efficiency. The combination of 3D conductive substrates, metal ion doping, and Bi₂WO₆ integration has shown potential in improving hematite’s photoelectrochemical performance. Novelty/Originality of this article: This review provides a comprehensive analysis of hematite performance enhancement strategies, focusing on the synergistic effects of 3D conductive substrates, Ti⁴⁺ doping, and Bi₂WO₆ integration.

Bridging the Gap between Molecular Simulations and Surface Complexation Modeling for Heterogeneous Surfaces: A Case Study with Uranium and Arsenic Adsorption on Clay Minerals.

Among all natural submicrosized phases, clay minerals are ubiquitous in soils and sedimentary rocks in nature as well as in engineered environments, and while clay minerals' adsorption properties have been studied extensively, their unique level of surface reactivity heterogeneities necessitates further investigation at the molecular level to understand and predict the influence of these heterogeneities on their macroscopic properties. In this study, we investigated the surface structures and desorption-free energies of U(VI) species (UO22+) and As(V) species (H2AsO4- and HAsO42-) complexed at different edge surface reactive sites of a cis-vacant montmorillonite layer using first-principles molecular dynamics (FPMD). We show that U(VI) forms bidentate and tridentate complexes on montmorillonite edge surfaces, whereas As(V) monodentate complexes are the most stable. Then, we constrained a state-of-the-art surface complexation model (SCM) with surface acid-base chemistry and surface complexation properties obtained from the molecular-level simulation results. While our results highlighted the complexity of the interfacial chemistry controlling the complexation of inorganic contaminants on clay mineral surfaces, they also evidenced the reliability of an integrated workflow using modern multiscale simulation techniques to address the challenge of predicting heterogeneities in mineral surface reactivity.

Enhanced CO2 Hydrogenation Performance of CoCrNiFeMn High Entropy Alloys

CO2 hydrogenation is a promising process for removing anthropogenic CO2 emissions and yielding C1 chemicals that can be utilized as fuels and valuable precursors for chemical synthesis. Commercial high-entropy alloys (HEAs) have widespread application in various fields owing to their exceptional thermal stability and tunable microstructure. However, their potential application as catalysts is often limited by the low exposure of active sites. In this study, the commercial CoCrNiFeMn powder was applied for atmospheric pressure CO2 hydrogenation and enhanced its catalytic performance by a combined treatment of ball milling and high-temperature H2 reduction. The high-energy ball milling results in a morphological transition in CoCrNiFeMn HEAs from spherical to irregular. This transformation leads to a significant decrease in particle size and more surface reactive sites. The high-temperature H2 reduction promoted the atomic rearrangement on the CoCrNiFeMn surface, thereby improving its alloy structural homogeneity. These modifications greatly improve the performance of CoCrNiFeMn for CO2 hydrogenation. This work introduces a facile modification approach to facilitate the catalytic efficiency of commercial HEAs in CO2 hydrogenation with high selectivity.

Interaction and kinetics of H2, CO2, and H2O on Ti3C2Tx MXene probed by X-ray photoelectron spectroscopy

One of the most explored MXenes is Ti3C2Tx, where Tx is designated to inherently form termination species. Among many applications, Ti3C2Tx is a promising material for energy storage, energy conversion, and CO2-capturing devices. However, active sites for adsorption and surface reactions on the Ti3C2Tx-surface are still open questions to explore, which have implications for preparation methods when to obtain correct and optimized surface requirements. Here we use X-ray photoelectron spectroscopy (XPS) to study the adsorption of common gas molecules such as H2, CO2, and H2O, which all may be present in energy storage, energy converting, and CO2-capturing devices based on Ti3C2Tx. The study shows that H2O, with a strong bonding to the Ti-Ti bridge-sites, can be considered as a termination species. An O and H2O terminated Ti3C2Tx-surface restricts the CO2 adsorption to the Ti on-top sites and may reduce the ability to store positive ions, such as Li+ and Na+. On the other hand, an O and H2O terminated Ti3C2Tx-surface shows the capability to split water. The results from this study have implications for the correct selection of MXene preparations and the environment around the MXene in different implementations, such as energy storage, CO2-capturing, energy conversion, gas sensing, and catalysts.

2D/2D Hydrogen‐Bonded Organic Frameworks/Covalent Organic Frameworks S‐Scheme Heterojunctions for Photocatalytic Hydrogen Evolution

AbstractHydrogen‐bonded organic frameworks (HOFs) demonstrate significant potential for application in photocatalysis. However, the low efficiency of electron‐hole separation and limited stability inhibit their practical utilization in photocatalytic hydrogen evolution from water splitting. Herein, the novel dual‐pyrene‐base supramolecular HOF/COF 2D/2D S‐scheme heterojunction between HOF‐H4TBAPy (Py‐HOF, H4TBAPy represents the 1,3,6,8‐tetrakis (p‐benzoic acid) pyrene) and Py‐COF was successfully established using a rapid self‐assembly solution dispersion method. Experimental and theoretical investigations confirm that the size‐matching of two crystalline porous materials enables the integrated heterostructure material with abundant surface reaction sites, strong interaction, and an enhanced S‐scheme built‐in electric field, thus significantly improving the efficiency of photogenerated charge carrier separation and stability. Notably, the optimal HOF/COF heterojunction achieves a photocatalytic hydrogen evolution rate of 390.68 mmol g−1 h−1, which is 2.28 times higher than that of pure Py‐HOF and 9.24 times higher than that of pure COF. These findings precisely acquire valuable atomic‐scale insights into the ingenious design of dual‐pyrene‐based S‐scheme heterojunction. This work presents an innovative perspective for forming supramolecular S‐scheme heterojunctions over HOF‐based semiconductors, offering a protocol for designing the powerful and strong‐coupling S‐scheme built‐in electric fields for efficient solar energy utilization.

Engineering ZnIn2S4 Nanosheets with Zinc Vacancies: Unleashing Enhanced Photocatalytic Degradation of Tetracycline.

Defect engineering is a highly effective strategy for accelerating charge transfer and enhancing the performance of photocatalysts. In this study, ZnIn2S4 nanosheets were designed and prepared with controlled Zn vacancies to optimize the electronic band structure and localized charge density of ZnIn2S4. EPR results confirmed the formation of Zn vacancies. This modification enabled efficient capture of photoexcited charges in defect centers, thereby prolonging the carrier's lifetime. Theoretical calculations demonstrated that these vacancies induced the formation of new defect states and highly efficient surface reaction sites. As anticipated, under visible light irradiation, the photocatalytic tetracycline removal rate of the ZnIn2S4 nanosheets with Zn vacancies reached 82.8% within 60 min, significantly higher than that observed for the pristine ZnIn2S4 sample. These findings offer valuable insights into the deliberate construction of metal-vacancy-containing photocatalytic nanomaterials for the enhanced degradation of micropollutants.

2D/2D Hydrogen-Bonded Organic Frameworks/Covalent Organic Frameworks S-Scheme Heterojunctions for Photocatalytic Hydrogen Evolution.

Hydrogen-bonded organic frameworks (HOFs) demonstrate significant potential for application in photocatalysis. However, the low efficiency of electron-hole separation and limited stability inhibit their practical utilization in photocatalytic hydrogen evolution from water splitting. Herein, the novel dual-pyrene-base supramolecular HOF/COF 2D/2D S-scheme heterojunction between HOF-H4TBAPy (Py-HOF, H4TBAPy represents the 1,3,6,8-tetrakis (p-benzoic acid) pyrene) and Py-COF was successfully established using a rapid self-assembly solution dispersion method. Experimental and theoretical investigations confirm that the size-matching of two crystalline porous materials enables the integrated heterostructure material with abundant surface reaction sites, strong interaction, and an enhanced S-scheme built-in electric field, thus significantly improving the efficiency of photogenerated charge carrier separation and stability. Notably, the optimal HOF/COF heterojunction achieves a photocatalytic hydrogen evolution rate of 390.68 mmol g-1 h-1, which is 2.28 times higher than that of pure Py-HOF and 9.24 times higher than that of pure COF. These findings precisely acquire valuable atomic-scale insights into the ingenious design of dual-pyrene-based S-scheme heterojunction. This work presents an innovative perspective for forming supramolecular S-scheme heterojunctions over HOF-based semiconductors, offering a protocol for designing the powerful and strong-coupling S-scheme built-in electric fields for efficient solar energy utilization.

Strong Metal–Support Interaction Induces Dual Reaction Sites for Ultrasensitive and Stable NO2 Detection in Extreme Environments

AbstractThe tripartite combination of a high density and stability of surface reaction sites, complemented by the longevity and efficient transfer of interface carriers, along with the effective adsorption and activation of target gas molecules, jointly determines the efficiency of chemiresistors. In this work, the strong metal–support interaction (SMSI) of Pt─Ce3+ is formed by the NaBH4 reduction method and thus prepares metal‐dynamically stable PtNR─CeO2 with Pt─Ce3+ and Pt─Pt reaction sites. The formation of SMSI induces the recombination of the chemical structure of the CeO2 surface causing the localization of electron‐rich Ce3+, which greatly increases the charge concentration at the interface. The experimental findings of the strong interaction of Pt─Ce3+ bonding and the catalytic effect of Pt optimized the adsorption mode of PtNR─CeO2 on target gas, which maintains stable catalytic activity at 20–500 °C and achieving a notable detection response value of 1.43 for 20 ppb NO2. This work offers fresh insights into designing stable oxide chemiresistors with efficiency and stability by customizing reaction sites at the atomic level.

Heterovalent State and Oxygen Vacancy Defect Structure‐Associated V/S Co‐Doped SnO2 for Catalytic Reduction of Organic and Cr6+ Pollutants in the Dark

AbstractV/S co‐doped SnO2 bimetal sulfur‐oxides catalysts labeled as (Sn,V)1‐x(S,O)2‐y or (SnVSO) with heterovalent state and oxygen vacancy defect are prepared via a green and facile method. The presence of SnVSO in the heterovalent states of Sn4+/Sn2+ and V5+/V4+ facilitates the rapid transfer of the electrons. It improves the electronic charge lifetime, accelerating the efficiency of the catalytic reduction of pollutants. The V/S co‐doped SnO2 regulates the bandgap energy structure. The hydrazine adjusts the heterovalent metal states to reduce Sn4+ to Sn2+ and V5+ to V4+. Also, it introduces oxygen vacancies to SnVSO to maintain the charge equilibrium and increase the active surface reactive sites, which enhance the catalytic activity. The SnVSO‐3 prepared with 0.4 mL hydrazine exhibits excellent catalytic activity, which wholly reduces 20 ppm of 100 mL methyl orange (MO), rhodamine B (RhB), methylene blue (MB), hexavalent chromium (Cr6+), and 4‐nitrophenol (4‐NP) within 6 min. In addition, the SnVSO‐3 also has good stability after repeated 6 runs with a reduction efficiency of 96.8%. Therefore, the V/S co‐doped SnO2 sulfur oxide catalysts have a promising potential for reducing Cr6+ and organic pollutants.

Controlling size and distribution of Au nano-particles on C3N4 for high-efficiency photocatalytic hydrogen production.

With advantages such as low cost, high stability, and ease of production, visible light photocatalytic C3N4 with a unique microscopic layered structure holds significant potential for development. However, its hydrogen production efficiency remains low due to the pronounced recombination of photo-generated charge carriers and limited surface reaction sites. Normally, the photocatalytic performance of C3N4 can be enhanced by loading noble metals with surface plasmon resonance. It is worth noting that the size of noble metal nanoparticles has a great influence on photocatalytic performance. In this study, accurate controlling of the size and distribution of Au nanoparticles was achieved on the surface of C3N4 by introducing amino groups to improve photocatalytic performance. Results show that uniformly distributed Au nanoparticles in the range of 2-6nm can be obtained on C3N4 with a remarkable enhancement of hydrogen production efficiency, which is about 114 times the property of pure C3N4. The small-sized and uniformly distributed Au nanoparticles can provide more reaction sites and increase the separation of photo-generated charge carriers, in turn improving Au/NH3-C3N4 photocatalytic hydrogen release rate to 6.85 mmol g-1h-1. This work offers a facile way to enhance photocatalytic performance by controlling the size of metal nanoparticles on C3N4 precisely.

Modulating g-C3N4 photocatalyst for H2 production via water splitting: The impact of Schiff base incorporation

This study explores the potential for improved photocatalytic activity by tailoring the properties of two-dimensional graphitic carbon nitride (g-C3N4) through non-metallic molecule modifications. Herein, melamine monomers were thermally polymerized in the presence of organic materials, namely (E)-2-((phenylimino)methyl) phenol, (E)-4-(benzylideneamino)benzoic acid, and (E)-4-((hydroxybenzylidene)amino)benzoic acid, to produce g-C3N4-PMP, g-C3N4-BAB, and g-C3N4-HBAB nanosheet composites, respectively. The investigated Schiff bases offer a variety of functionalities capable of influencing the electronic structure, surface reactive sites, and porosity. Consequently, all of the modified composites exhibited higher efficiency in photocatalytic hydrogen generation compared to pristine g-C3N4. Notably, the highest catalytic activity was observed for g-C3N4-PMP, with a rate of 1148 µmol•g−1•h−1, which is seven times greater than that of g-C3N4. Optical and photoelectrochemical properties of the photocatalysts were analyzed to develop a workable mechanism for photocatalysis. The utilization of organic Schiff bases in conjunction with melamine for the g-C3N4 synthesis presents a versatile approach to tailor the properties and augment the photocatalytic performance of the resulting nanocomposite material for diverse environmental and energy-related applications.

Density functional theory and spectroscopic analysis of stigmasterol from Garcinia wightii: Deciphering its inhibitory potential against drug-resistant tuberculosis via insilico molecular docking and molecular dynamics simulations

This study investigates the molecular structure and electronic properties of stigmasterol, isolated from Garcinia wightii, using density functional theory (DFT) alongside experimental techniques including FT-IR, FT-Raman, UV–Vis, 1H and 13C NMR spectroscopy. Theoretical predictions are compared with experimental results, facilitated by vibrational energy distribution analysis for unambiguous vibrational wavenumber assignments. Natural bond orbitalanalyzes reveal donor-acceptor bond energies and electron densities, while Fukui functions identify reactive sites susceptible to electrophilic and nucleophilic attacks. Electronic properties are further explored through various analyzes, unveiling reactive surface sites. Non-covalent interactions are examined using reduced density gradient analysis. Assessment of absorption, distribution, metabolism, and excretion attributes aids in drug discovery efforts. Molecular docking studies against 20 target proteins for antitubercular screening show a stable glide score of -9.52 kcal/mol for the protein 4FDO (Mycobacterium tuberculosis DprE1 in complex with CT319). Molecular dynamics simulations over 100 ns indicate the stability of the ligand-protein complex, suggesting its potential as an antituberculosis agent. Stigmasterol's structural, vibrational, electronic, and topological properties are thoroughly investigated, revealing its ring skeleton with a flexible isooctyl side chain, adhering to C1 point group symmetry. Steric and stereo electronic interactions play crucial roles in conformation and binding to target proteins. Theoretical and experimental analyzes align, confirming the compound's bioactive properties. This comprehensive investigation underscores stigmasterol's potential as a tuberculosis treatment option, providing valuable insights into its structural characteristics and therapeutic possibilities.

Prior thermal and high-pressure processing alters the impact of high intensity ultrasound on reconstituted skim milk

Reconstituted skim milk was subjected to heat treatment at 85 °C for 20 min or high pressure processing (HPP) at 400 or 600 MPa for 15 min with or without subsequent high intensity ultrasound (US) at 68 kHz, 500 W for 15 min at 30 °C. Untreated and treated samples were analyzed for particle size distribution, zeta potential, surface hydrophobicity, and concentration of total and surface sulfhydryl groups in addition to Native- and SDS-PAGE of serum phase upon ultracentrifugation and pH adjustment. Preceding heat- and HPP altered the impact of the subsequent US treatment, demonstrating process- and intensity-dependent exposure and burial of surface reactive sites on milk proteins respectively. US following HPP promoted sedimentation of HPP-dispersed serum casein fractions, while US following heat was directed mainly at the whey proteins originally bound to the micelles. The primary US effect on the untreated and treated milk proteins was at the molecular level.

Particle Size-Tunable Polydopamine Nanoparticles for Optical and Electrochemical Imaging of Latent Fingerprints on Various Surfaces.

Powder dusting method is the most widely used approach due to its low cost, simplicity, minimal instrument dependence, and extensive applicability for developing latent fingerprints (LFPs). Herein, a novel optical and electrochemical dual-mode method for high-resolution LFP enhancement has been explored based on size-tunable polydopamine (PDA) nanoparticles (NPs) and scanning electrochemical microscopy (SECM). Dark PDAs rich in functional groups and negative charges can combine with the residues of LFPs on various surfaces with high sensitivity and selectivity to realize high-resolution visual fingerprint physical patterns on various porous and nonporous substrates with light color. However, optical visualization is not feasible for LFPs on dark or multicolored surfaces. Fortunately, based on the differences in electrochemical reactivity between ridges and furrows caused by the conductivity and reducibility of PDA powders, SECM can serve as a powerful supplement to optical methods to effectively overcome background color interference and distinctly display fingerprint patterns. Intriguingly, it is noteworthy that the binding amount and particle size of PDA powder significantly affected the optical and electrochemical visualization of LFPs: more powder binding amounts provided darker ridges in optical, and more surface reaction sites (larger powder binding mass at the same particle size or smaller particle size at the same mass) provided higher currents of ridges in electrochemical imaging. It demonstrates that the PDA powder as a dual-mode developer for LFPs offers a promising method for individual identification in forensics.

Oxidation of antibiotic micropollutants in various water resources through integration of Bi2WO6 and g-C3N4.

Recently, the hazardous effects of antibiotic micropollutants on the environment and human health have become a major concern. To address this challenge, semiconductor-based photocatalysis has emerged as a promising solution for environmental remediation. Our study has developed Bi2WO6/g-C3N4 (BWCN) photocatalyst with unique characteristics such as reactive surface sites, enhanced charge transfer efficiency, and accelerated separation of photogenerated electron-hole pairs. BWCN was utilized for the oxidation of tetracycline antibiotic (TCA) in differentwater sources. It displayed remarkable TCA removal efficiencies in the following order: surface water (99.8%) > sewage water (88.2%) > hospital water (80.7%). Further, reusability tests demonstrated sustained performance of BWCN after three cycles with removal efficiencies of 87.3, 71.2 and 65.9% in surface water, sewage, and hospital water, respectively. A proposed photocatalytic mechanism was delineated, focusing on the interaction between reactive radicals and TCA molecules. Besides, the transformation products generated during the photodegradation of TCA were determined, along with the discussion on the potential risk assessment of antibiotic pollutants. This study introduces an approach for utilizing BWCN photocatalyst, with promising applications in the treatment of TCA from various wastewater sources.

Novel MnCo2O4/YVO4 heterostructure for promoting photocatalytic oxidative desulfurization of thiophene under visible light

In this work, for the first time, the photocatalytic oxidative desulfurizing of thiophene through exposure to visible light was performed on mesoporous MnCo2O4/YVO4 heterojunctions. Mesoporous YVO4 nanocrystals were combined with MnCo2O4 nanoparticles (NPs) to construct MnCo2O4/YVO4 heterostructure candidates using an easy sol-gel approach. The constructed mesoporous YVO4 with a tetragonal structure has a large surface area of approximately 200.0 m2 g−1. Within 90-min visible light exposure, the 9.0 wt% MnCo2O4/YVO4 nanocomposite photocatalyst exhibited 100.0 % desulfurization efficacy, which was ∼25.0 folds greater than occurred using the unmodified YVO4 (only 4.0 %). Notably, the 9.0 wt% MnCo2O4/YVO4 photocatalyst displayed a desulfurization rate of ca. 269.19 μmol L−1 min−1, which was ∼55.00 folds higher than that occurred on the unmodified YVO4 material (4.90 μmol L−1 min−1). The constructed MnCo2O4/YVO4 heterostructure exhibited preeminently superb photocatalytic thiophene oxidation with superior recyclability than nonmodified YVO4. The n-n heterojunction construction between MnCo2O4 and YVO4 played a major role in synergistic promoting the photocatalytic efficacy of the MnCo2O4/YVO4 nanocomposite through enlarging the photoabsorbance capability and promoting photoexcited carriers’ separation. Moreover, the abundant surface reactive sites originating from the mesoporous nature of the constructed heterostructure candidates significantly contributed to enhancing the photocatalytic thiophene oxidation. The 9.0 wt% MnCo2O4/YVO4 candidate exhibited high stability within 600.0 min. Overall, this contribution not only presents a new MnCo2O4/YVO4 heterojunction, fabricated by an easy approach for highly efficient desulfurizing of thiophene but also provides good ideas for establishing other heterostructure materials.

The Capture of Cadmium from Solution during the Replacement of Calcite by Apatite.

The capture of cadmium (Cd) from phosphate-containing solutions during the replacement of CaCO3 by phosphate phases such as hydroxylapatite (HAP) and tricalcium phosphate (TCP) has been studied under high and low temperature and pressure conditions using atomic force microscopy, scanning electron microscopy equipped with an X-ray spectrometer and a backscattered electron detector, Raman spectroscopy, and microprobe analysis. Starting with cubes of Carrara Marble (polycrystalline calcite) and single crystals of calcite, a new solid phosphate phase was observed to incorporate Cd from solution, formed under different pressure and temperature conditions tested. Results showed that Cd precipitated in a new phase on the surface of all samples tested. In Carrara Marble, pseudomorphic replacement of CaCO3 is restricted possibly due to kinetic limitation caused by the adsorption of Cd complexes formed in solution at reactive surface sites and the variation of fluid composition inside the sample. However, on the sample surface, this kinetic limitation is less influential, so the new phase could incorporate higher amounts of Cd faster. Furthermore, this reaction at room temperature was found to have similar and/or better Cd-uptake efficiency as HAP and CaCO3 in pure Cd solution through the precipitation of Cd-containing phosphate crystals on the sample surface. Both reactions were able to capture Cd in the precipitating phase structure and could provide a mechanism for simultaneous Cd and phosphate removal from solutions contaminated with both, in industrial or natural settings.

Oxygen vacancy induced strong interfacial electric field for boosting photocatalytic degradation of tetracycline

Heterojunction construction is an effective strategy to improve the photocatalytic performance of a single semiconductor, but the interfacial electric field (IEF) is often weak, and this strategy cannot solve the problem of few surface reactive sites, resulting in limited catalytic activity improvement of heterojunctions. In this work, we constructed a Z-scheme structure with oxygen vacancies (Ovs) by in situ growth of OV-rich BiOI (Vo-BiOI) crystals on the surface of CTAB-modified g-C3N4 (BCN) flakes. The IEF between BCN and Vo-BiOI offers a strong driving force to accelerate direct Z-scheme charge transfer evidenced by in-situ Kelvin probe force microscopy (KPFM) and theoretical calculations. In addition, the BCN/Vo-BiOI possesses a high adsorption and activation capacity of pollutant molecules due to the surface CTAB modification on g-C3N4 and introducing Ovs on the surface of BiOI. Thus, this unique Z-scheme heterojunction generates more •OH and •O2- for tetracycline (TC) degradation, and the degradation rate reaches 0.0260 min−1, which is 32.5 times that of pure g-C3N4. Output of this work may provide a good avenue for development of efficient and versatile novel photocatalytic materials.

3D Tremella‐Like g‐C3N4/TiO2/HNTs Heterojunction Photocatalyst for Enhanced Photocatalytic Degradation of Rhodamine B From Water

AbstractAmong the traditional treatment processes for purifying wastewater contaminated with Rhodamine B (RhB), semiconductor photocatalysis is the most effective technology because it can oxidize organic pollutants and convert them into CO2, H2O, and other harmless molecules in a safe and efficient manner. According to literature research, it is feasible to enhance the performance of g‐C3 N4 as a photocatalyst by constructing a heterojunction with other photocatalytic materials. Morphological regulation of carbon nitride (g‐C3N4) is a viable strategy for improving its photocatalytic activities. By controlling the morphology of g‐C3N4, factors such as light absorption, specific surface area, charge separation, and reaction sites can be optimized to enhance its photocatalytic efficiency. Three‐dimensional tremella‐like carbon nitride (3DT‐CN) and 3D‐CN/TiO2/HNTs (halloysite nanotubes) were prepared using bubble templates and an impregnation method respectively. The Z‐scheme heterojunction structure constructed by 3D‐CN and TiO2 promotes electron‐hole separation. Catalytic experiments demonstrated that under irradiation for 120 min, the 3D‐CN/TiO2/HNTs catalyst could eliminate 86.48 % of Rhodamine B (RhB). Additionally, active radicals such as e‐, h+, ⋅OH, and ⋅O2‐ are involved in RhB degradation. Therefore, the three‐dimensional tremella‐like 3D‐CN/TiO2/HNTs heterojunction photocatalyst has great potential for environmental purification.

Preferential heteroatom substitution into ZnIn2S4 nanosheets boosts photocatalytic hydrogen production

Interior modification through preferential substitution of heteroatoms in 2D materials can rescue surface reactive sites for enhanced charge kinetics and photo-activity. Here, Ru and Ni heteroatoms were successfully incorporated in ZnIn2S4 (ZIS) nanosheets via a simple hydrothermal technique. Ru-ZIS photocatalysts exhibited improved photo–water splitting activity (26,400 µmol. h−1g−1) and good stability than that of Ni-ZIS and pristine ZIS under simulated sunlight, which may be related to the increase in reactive sites with Ru substitution, optimized adsorption-free energy of the reaction intermediates and charge kinetics. Ru substitution influenced Zn site availability and thus coordinated bonding with surrounding S ions. Ru-ZIS showed excellent hydrogen evolution performance and minimal change in Gibbs free energy (ΔGH, ∼0 eV). By analyzing the density of states, both Ru and S sites had greater H* intermediate absorption abilities. This study elaborates on the effect of preferential heteroatom substitution on photocatalytic performance and has widespread applications.