High-angle Annular Dark-field Scanning Research Articles

Effect of boron and nitrogen modulation in metal atoms anchoring on flower-like carbon superstructure for efficient ammonia electrosynthesis

Electrocatalytic nitrogen reduction reaction (NRR) is regarded as an ideal alternative technology to the conventional ammonia synthesis. The best way to improve the yield and Faraday efficiency (FE) of the electrocatalytic NRR is the development of low-cost, stable, and efficient catalysts. Herein, a boron-based Zn-metal–organic framework is used to prepare metal atoms (Fe) anchored on B/N co-doped carbon (Fe-B/N-C) as efficient NRR catalysts. Fe-B/N-C shows an excellent NRR performance (with the maximum ammonia yield of 100.1 μg·h−1·mgcat-1 and the maximum FE of 23.0%), which are superior to most of the reported NRR catalysts. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) demonstrate that Fe atoms can achieve an atomic-level dispersion on the flower cluster-like superstructure and coordinate with N atoms to form Fe-N sites. Theoretical calculations show that in the Fe-N4-B, the boron atom in the substrate can reduce the energy barrier of both the nitrogen activation and the rate-determining step (RDS) of NRR, and the distal pathway of association mechanism is more favorable. This work provides a new insight into the effect of dual-atom doping on the NRR process and kinetics, which is important to the development of high-performance NRR catalysts.

Mesoporous Fe3O4 nanoparticle: A prospective nano heat generator for thermo-therapeutic cancer treatment modality

In the present work, we have synthesized Fe3O4 MNPs with a mesoporous feature by the solvothermal process. Through iteration of experiments, we found that the specific solvent helped in stabilizing the mesoporous structure. We have used techniques, such as transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to study the structural features of the sample. The material demonstrated effective heating under an alternating magnetic field (AMF), and the concentration of aqueous ferro-fluid influences the same. The experimental intrinsic loss power (ILP) value of ∼ 5.30 ± 0.25 nHm2kg−1 is suggestively higher than the commercially available ferro-fluids and equivalent to previously reported values for iron oxide MNPs. The material demonstrated an impressive heating performance under near infra-red (NIR) irradiation with a concentration as small as 0.1 mg/mL. The photoluminescence (PL) spectroscopy has allowed corroborating the efficient heating behaviour of the material under NIR irradiation. An effective decrease in SiHa cells viability was observed after NIR exposure with concentration of 250 and 500 μg/mL of MNPs. We believe this work will pave a new pathway in the area of biomaterials thermo-therapeutic cancer treatment with improved efficacy via mesoporous structure, efficient heating under NIR exposure and high ILP value.

Designing a Bifunctional Pt/Cu-SSZ-13 Catalyst for Ammonia-Selective Catalytic Oxidation with Superior Selectivity

Ammonia-selective catalytic oxidation (NH3-SCO) is an effective technology to solve the problem of ammonia leakage from diesel vehicles, while ammonia oxidation catalysts (AOC) still suffer from insufficient low-temperature activity and poor nitrogen selectivity. Herein, we prepared a bifunctional Pt/Cu-SSZ-13 catalyst containing an SCO component (Pt) and a selective catalytic reduction (SCR) component (Cu). This bifunctional catalyst exhibited excellent catalytic performance during NH3 oxidation under practical conditions containing water vapor, achieving >85% N2 selectivity over the whole temperature range. Catalysts were systematically characterized by Brunauer–Emmett–Teller, X-ray diffraction, inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, NH3 temperature-programmed desorption, high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption fine structure analysis. The results showed that metallic Pt nanoparticles were mainly present on the exterior surface of the Pt/Cu-SSZ-13 zeolite catalyst, while dispersed Cu2+ cations were present in the interior of the zeolite. Based on operando diffuse reflectance infrared Fourier transform spectroscopy with mass spectrometry experiments, it was confirmed that on Pt/SSZ-13, over-oxidation of NH3 produced large amounts of N2O and NOx at low and high temperatures, respectively, resulting in a poor N2 selectivity. With Cu present, in contrast, the byproduct (NO) would further react with adsorbed NH3 on Cu Lewis acid sites to produce N2 by a tandem SCR reaction, thus contributing to the superior N2 selectivity of the Pt/Cu-SSZ-13 bifunctional catalyst.

Hollow N-doped carbon spheres with anchored single-atom Fe sites for efficient electrocatalytic oxygen reduction

We anchored atomically dispersed Fe-N4 sites on hollow N-doped carbon spheres (Fe SAs/HNCSs-800) for electrocatalytic ORR; the obtained material exhibited electrocatalytic activity and stability comparable to that of commercial Pt/C, with an onset potential of 0.925 V and a half-wave potential of 0.867 V. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectroscopy results confirmed the presence of highly dispersed Fe single atoms in Fe SAs/HNCSs-800. The results of experiments and theoretical calculations show that the single-atom dispersed Fe-N4 serve as the ORR active sites, and the adjacent C defects can effectively regulate the electronic structure of Fe atoms and improve the electrocatalytic ORR activity.

Annealing hardening effect aroused by solute segregation in gradient ultrafine-grained Mg-Gd-Zr alloy

In this study, a remarkable annealing hardening effect was detected in gradient ultrafine-grained (UFG) Mg-0.32Gd-0.11Zr (at.%) alloy sheet fabricated by sliding friction treatment (SFT). Under the precipitation-free condition, the annealed UFG structure shows an obvious hardness increment from 1.40 GPa to 1.89 GPa after 200°C heating for 12 h, which exhibits a much higher hardening response than the annealed coarse-grained (CG) structure. The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and elemental mapping reveal prominent segregation of solute Gd atoms along grain boundaries, which endows the UFG structure with excellent grain boundary stability. Moreover, Gd segregation is also found around the extrinsic stacking fault (E-SFs) and the low-angle grain boundaries composed of edge dislocations. The large-scale solute partitioning provides a significant segregation hardening effect, which completely resists the softening effect aroused by the grain coarsening and dislocation annihilation. This work realizes a good combination of surface mechanical processing for fabricating UFGs and subsequent heat treatment, which earns desirable segregation hardening effects.

Effects of CrxMo(0.2-x) addition on the dispersoids evolution and mechanical properties of Al–Cu–Mg–Ag–Mn alloy

Unlike the rod-like T–Al20Cu2Mn3 dispersoids, the spherical Al7(Cr, Mn) and Al6(Fe, Mn, Mo) precipitated in Al–Cu–Mg–Ag–Mn alloys with CrxMo(0.2-x) addition, retained the deformed substructure, and acted as a dispersion reinforcement. In this study, the precipitation behavior of dispersoids in Al–Cu–Mg–Ag–Mn alloys with various CrxMo(0.2-x) (x = 0.15, 0.10, 0.05 wt.%) at 400 °C/12 h + 515 °C/24 h homogenization was investigated. The compositional and structural evolution of dispersoids in Al–Cu–Mg–Ag–Mn alloys were investigated by optical microscopy and atomic resolution high-angle annular dark-field scanning transmission electron microscopy. The effects of CrxMo(0.2-x) addition on morphology, size and number density of dispersoids inhibited the recrystallization behavior and improved the mechanical properties of alloys in varying degrees. When x = 0.15 in CrxMo(0.2-x), the large amount of Al7(Cr, Mn) precipitates to refine the T–Al20Cu2Mn3, and dispersoid-free zones (DFZ) significantly decreases. As x decreases to 0.05, the homogeneous Al6(Fe, Mn, Mo) dispersoids present the opposite precipitation trend of T–Al20Cu2Mn3 to compensate for the DFZ. During the deformation and subsequent heat treatment, the Al–Cu–Mg–Ag–Mn alloy with Cr0.05Mo0.15 addition maintains the highest substructure and dislocation density owing to the highest number density of spherical dispersoids, demonstrating excellent mechanical properties at ambient and elevated temperatures.

Atomic Insights into the Cu Species Supported on Zeolite for Direct Oxidation of Methane to Methanol via Low-Damage HAADF-STEM.

Precise determination of the structure-property relationship of zeolite-based metal catalysts is critical for the development toward practical applications. However, the scarcity of real-space imaging of zeolite-based low-atomic-number (LAN) metal materials due to the electron-beam sensitivity of zeolites has led to continuous debates regarding the exact LAN metal configurations. Here, a low-damage high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging technique is employed for direct visualization and determination of LAN metal (Cu) species in ZSM-5 zeolite frameworks. The structures of the Cu species are revealed based on the microscopy evidence and also proved by the complementary spectroscopy results. The correlation between the characteristic Cu size in Cu/ZSM-5 catalysts and their direct oxidation of methane to methanol reaction properties is unveiled. As a result, the mono-Cu species stably anchored by Al pairs inside the zeolite channels are identified as the key structure for higher C1 oxygenates yield and methanol selectivity for direct oxidation of methane. Meanwhile, the local topological flexibility of the rigid zeolite frameworks induced by the Cu agglomeration in the channels is also revealed. This work exemplifies the combination of microscopy imaging and spectroscopy characterization serves as a complete arsenal for revealing structure-property relationships of the supported metal-zeolite catalysts.

Na+ Lattice Doping Induces Oxygen Vacancies to Achieve High Capacity and Mitigate Voltage Decay of Li-Rich Cathodes.

In this work, we synthesized 1D hollow square rod-shaped MnO2, and then obtained Na+ lattice doped-oxygen vacancy lithium-rich layered oxide by a simple molten salt template strategy. Different from the traditional synthesis method, the hollow square rod-shaped MnO2 in NaCl molten salt provides numerous anchor points for Li, Co, and Ni ions to directly prepare Li1.2Ni0.13Co0.13Mn0.54O2 on the original morphology. Meanwhile, Na+ is also introduced for lattice doping and induces the formation of oxygen vacancy. Therefrom, the modulated sample not only inherits the 1D rod-like morphology but also achieves Na+ lattice doping and oxygen vacancy endowment, which facilitates Li+ diffusion and improves the structural stability of the material. To this end, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and other characterization are used for analysis. In addition, density functional theory is used to further analyze the influence of oxygen vacancy generation on local transition metal ions, and theoretically explain the mechanism of the electrochemical performance of the samples. Therefore, the modulated sample has a high discharge capacity of 282 mAh g-1 and a high capacity retention of 90.02% after 150 cycles. At the same time, the voltage decay per cycle is only 0.0028 V, which is much lower than that of the material (0.0038 V per cycle) prepared without this strategy. In summary, a simple synthesis strategy is proposed, which can realize the morphology control of Li1.2Ni0.13Co0.13Mn0.54O2, doping of Na+ lattice, and inducing the formation of oxygen vacancy, providing a feasible idea for related exploration.

Insights into the microstructures and mechanical properties of magnesium–calcium–transition elements: A combined experimental and simulation study

Small amounts of transition elements: Ti, Mn, Fe, Co, and Ni, have been added to a Mg–0.1Ca (wt%) alloy to elucidate their additions on the microstructure and room temperature (RT) mechanical properties. Only Ni was effective in weakening the texture intensity and thus led to the improvement in RT formability and ductility, whereas the other elements were basically no effect. The microstructural characterization by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) in conjunction with energy-dispersive X-ray spectrometry (EDS) and numerical simulation using a grain boundary (GB) phase model indicates that the Ca and Ni co-segregated to the GB of the Ni-containing alloy, while the GB of the other alloys was enriched with Ca only. Further investigations by a correlative electron backscatter diffraction and STEM-EDS reveal that the transverse direction (TD) oriented GBs had significantly lower concentration of Ca and Ni compared to the basal-oriented GBs, which resulted in the development of the TD-split texture in the Ni-containing alloy. A compositionally optimized Mg–0.1Ca–0.1Ni (wt%) alloy showed a large index Erichsen value of 8.5 mm in the sheet form, and exhibited a high tensile yield strength of 238 MPa with a moderate fracture elongation of 14% in the form of an extruded rod. Due to the addition of small amounts of alloying elements, the newly developed Mg–0.1Ca–0.1Ni alloy had an excellent thermal conductivity of 154 W/(m·K) which is even higher than that of a commercial 5052 Al alloy.

On the origin of carrier localization in AlInAsSb digital alloy

We compared the photoluminescence (PL) properties of AlInAsSb digital alloy samples with different periods grown on GaSb (001) substrates by molecular beam epitaxy. Temperature-dependent S-shape behavior is observed and explained using a thermally activated redistribution model within a Gaussian distribution of localized states. There are two different mechanisms for the origin of the PL intensity quenching for the AlInAsSb digital alloy. The high-temperature activation energy E 1 is positively correlated with the interface thickness, whereas the low-temperature activation energy E 2 is negatively correlated with the interface thickness. A quantitative high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) study shows that the interface quality improves as the interface thickness increases. Our results confirm that E 1 comes from carrier trapping at a state in the InSb interface layer, while E 2 originates from the exciton binding energy due to the roughness of the AlAs interface layer.

Thermodynamically and Kinetically Stabilized Pt Clusters Against Sintering on CeO2 Nanofibers Through Enclosing CeO2 Nanocubes.

Sintering is a major concern for the deactivation of supported metals catalysts, which is driven by the force of decreasing the total surface energy of the entire catalytic system. In this work, a double-confinement strategy is demonstrated to stabilize 2.6nm-Pt clusters against sintering on electrospun CeO2 nanofibers decorated by CeO2 nanocubes (m-CeO2 ). Thermodynamically, with the aid of CeO2 -nanocubes, the intrinsically irregular surface of polycrystalline CeO2 nanofibers becomes smooth, offering adjacent Pt clusters with decreased chemical potential differences on a relatively uniform surface. Kinetically, the Pt clusters are physically restricted on each facet of CeO2 nanocubes in a nanosized region. In situ high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observation reveals that the Pt clusters can be stabilized up to 800°C even in a high density, which is far beyond their Tammann temperature, without observable size growth or migration. Such a sinter-resistant catalytic system is endowed with boosted catalytic activity toward both the hydrogenation of p-nitrophenol after being aged at 500°C and the sinter-promoting exothermic oxidation reactions (e.g., soot oxidation) at high temperatures over 700°C. This work offers new opportunities for exploring sinter-resistant nanocatalysts, starting from the rational design of whole catalytic system in terms of thermodynamic and kinetic aspects.

Direct Atomic-Scale Insight into the Precipitation Formation at the Lanthanum Hydroxide Nanoparticle/Solution Interface

Understanding precipitation formation at lanthanum hydroxide (La(OH)3) nanoparticle-solution interfaces plays a crucial role in catalysis, adsorption, and electrochemical energy storage applications. Liquid-phase transmission electron microscopy enables powerful visualization with high resolution. However, direct atomic-scale imaging of the interfacial metal (hydro)oxide nanostructure in solutions has been a major challenge due to their beam-driven dissolution. Combining focused ion beam and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, we present an atomic-scale study of precipitation formation at La(OH)3 nanoparticle interfaces after reaction with phosphate. The structure transformation is observed to occur at high- and low-crystalline La(OH)3 nanoparticle surfaces. Low-crystalline La(OH)3 mostly transformed and high-crystalline ones partly converted to LaPO4 precipitations on the outer surface. The long-term structure evolution shows the low transformation of high-crystalline La(OH)3 nanoparticles to LaPO4 precipitation. Because precipitation at solid-solution interfaces is common in nature and industry, these results could provide valuable references for their atomic-scale observation.

Effect of in-situ Zn doping on suppression of phase separation in InxAl1−xAs epitaxial layer on InP(001) grown by MOCVD

The effect of Zn impurities on the surface morphology evolution and phase separation behavior of the InAlAs layer on InP(001) substrates is investigated using metal organic chemical vapor deposition (MOCVD). The phase separation of InAlAs occurs at a relatively low growth temperature (T < 620 °C), accompanied by surface roughening and bandgap lowering. According to the microstructural analyses, indium (In) and aluminum (Al) atoms have high reactivity with In-rich or Al-rich columns in a certain growth region. The addition of Zn impurities during InAlAs growth at the phase-separating temperature results in the suppression of phase separation, which can be attributed to a high probability of Zn incorporation into the sites, which generates an In-rich and Al-rich phase column in the phase-separated InAlAs layer. Based on atomic force microscopy (AFM) and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) analysis, we classify four types of InAlAs surface morphology as a function of the growth temperature and flow rate of Zn impurities.

Study on microstructure and properties of AA7075 coated by micro arc oxidation

Effect of ageing temperature on the properties of 7075 aluminum alloy coated by micro arc oxidation (MAO) technology has been investigated. The precipitates formed at various ageing temperatures are observed by transmission electron microscope (TEM), which would significantly influence the properties of the MAO coating. Coherent distortion, size and volume fraction of precipitates are related to the changing of electrical conductivity during ageing treatment. Full coherent and dense Guinier Preston zones (GP zones) formed at 90 °C can act as scattering centers to impede electron mobility, so decrease the electrical conductivity. η and η′ phases produced at 120 °C and 150 °C are semi-coherent and incoherent, respectively, meanwhile, the precipitate size increases and the volume fraction decreases with increasing the ageing temperature, therefore, the electrical conductivity increases. Higher electrical conductivity contributes to thicker coating with better surface morphology. Double cantilever beam (DCB) tests show that the thicker and less porous coatings prepared at 150 °C aged specimens own the best stress corrosion cracking (SCC) resistance. After pores are broke and coatings are ruptured, high Cu and low Mg segregation at the grain boundary of 150 °C aged specimens founded from high-angle annular dark field scanning transmission electron microscopy (HADDF-STEM) are beneficial to anodic dissolution and hydrogen assisted crack.

Microstructure evolution and shearing behaviour of δꞌ/θꞌ/δꞌ precipitates in an aged Al-Cu-Li-Mg aluminium alloy

We report here on the microstructure evolution and the strengthening behaviour of the δꞌ/θꞌ/δꞌ precipitates in the aged Al-Cu-Li-Mg aluminium alloy by atomic high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and in-situ TEM compression straining. On the chosen zone axis, atomic HAADF-STEM images reveal the in-situ microstructure evolution of the δꞌ/θꞌ/δꞌ precipitates. A monolayer GP(θꞌ) zone, grown on the (001)Al plane, evolves from the Cu-rich region. After the transformation of the GP(θꞌ) zone to θꞌ phase, the boundaries of the θꞌ phase are coated with the δꞌ phases, forming a matured δꞌ/θꞌ/δꞌ precipitate. Additionally, the growth of δꞌ phases on the two sides of θꞌ is not affected by the inclined boundaries of θꞌ and the hard impingement of the thin T1 precipitate. During the in-situ TEM compression straining on the peak-aged nanopillar, the deviated slip band structures and the large displacement bursts are presumably associated with the dislocation-precipitate interaction of the T1 and δꞌ/θꞌ/δꞌ precipitates. Furthermore, evidence from atomic HAADF-STEM images shows that dislocations can cut the δꞌ/θꞌ/δꞌ precipitate, producing the stacking fault layers within the θꞌ phase of the sheared δꞌ/θꞌ/δꞌ precipitate.

Atomistic mechanism of η’-to-η transformation in Al-Zn-Mg-Cu alloys

The atomistic mechanism of η’-to-η transformation in aged Al-Zn-Mg-Cu alloys has been investigated by using high-angle annular dark-field scanning transmission electron microscopy and density functional theory calculations. The η’-to-η transformation is accomplished by the structure transition from the orthorhombic units into the rhombohedral units, where the outward diffusion of selective Zn atoms, shear in (111)Al plane and also the shuffle of certain atoms are involved. The interaction between vacancy and η’ is found to be able to assist the outward diffusion of Zn atoms and thus facilitate η’-to-η transformation. Via tuning the vacancy behaviours, a strategy to retard the coarsening of η’ is proposed, which would benefit the design of high-performance Al alloys toward application in harsh conditions.

Lattice-strained Pt nanoparticles anchored on petroleum vacuum residue derived N-doped porous carbon as highly active and durable cathode catalysts for PEMFCs

High cost and poor durability of Pt-based cathode catalysts for oxygen reduction reaction (ORR) severely hamper the popularization of proton exchange membrane fuel cells (PEMFCs). Tailoring carbon support is one of effective strategies for improving the performance of Pt-based catalysts. Herein, petroleum vacuum residue was used as carbon source, and nitrogen-doped porous carbon (N-PPC) was synthesized using a simple template-assisted and secondary calcination method. Small Pt nanoparticles (Pt NPs) with an average particles size of 1.8 nm were in-situ prepared and spread evenly on the N-PPC. Interestingly, the lattice compression (1.08%) of Pt NPs on the N-PPC (Pt/N-PPC) was clearly observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), which was also verified by the shift of (111) crystal plane of Pt on N-PPC to higher angles. The X-ray photoelectron spectroscopy (XPS) results suggest that the N-PPC support had a strong effect on anchoring Pt NPs and endowing surface Pt NPs with lowered d band center. Thus, the Pt/N-PPC as a catalyst simultaneously boosted the ORR activity and durability. The specific activity (SA) and mass activity (MA) of the Pt/N-PPC at 0.9 V reached 0.83 mA cm−2 and 0.37 A mgPt−1, respectively, much higher than those of the commercial Pt/C (0.21 mA cm−2 and 0.11 A mgPt−1) in 0.1 M HClO4. The half-wave potential (E1/2) of Pt/N-PPC exhibited only a minimal negative shift of 7 mV after 30,000 accelerated durability tests (ADT) cycles. More importantly, an H2–O2 fuel cell with a Pt/N-PPC cathode achieved a power density of 866 mW cm−2, demonstrating that the prepared catalyst has a promising application potential in working environment of PEMFCs.

Atomic-scale inhomogeneous solute distribution in an ultrahigh strength nanocrystalline Al-8 Mg aluminum alloy

Exploring the redistribution mechanism of Mg from the perspective of experimental observation has been a long-term yet challenging attempt in Al-Mg alloys. Here we demonstrate a simple but effective approach to obtain non-uniform Mg solute distribution (i.e., Mg-enriched/depletion zones) around typical grain boundaries (GBs) in a nanocrystalline Al-8 Mg alloy. This abnormal segregation was detected by both high-angle annular dark-field scanning transmission electron microscopy and atom probe tomography. The results show that local strain and GB migration during deformation leads to spatially inhomogeneous Mg solute distribution around the GBs. Both the non-uniform distribution and the broadened GBs can hinder GB migration and dislocation motion, thus enhance the strength. An inhomogeneous solute distribution mechanism of Mg atoms is proposed based on the extensive investigations. This study may help with developing new strengthening mechanisms of nanocrystalline materials.

Formation mechanism of trench defects in green InGaN/GaN multiple quantum wells

Trench defects, resulting in low emission efficiency in green and longer spectrum ranges, are widely observed in III-nitride alloy multiple quantum wells (MQWs), particularly in those with high indium content. There is a lack of understanding of the atomic formation mechanism of trench defects; however, it is crucial to the efficiency of devices. Here, we provided a thermodynamic analysis through first-principles calculations based on the density functional theory combined with experimental confirmation to reveal the atomic formation mechanism of trench defects in the InGaN MQWs system. The In-rich region is easy to form and induces basal plane stacking faults (BSFs) at the interface between the InGaN quantum well and the GaN quantum barrier (QB). The boundary between BSF and non-BSF regions exhibits a much slower growth rate due to the formation of homoelementary bonds, resulting in a V-shaped groove shape. Based on high-angle annular dark field scanning transmission electron microscopy, we observe the trench defects originating from the thick GaN QB layer due to the formation of closed-loop V-shaped grooves and the BSF. Besides, the cathodoluminescence measurements show that the InGaN QW within the defect has excess indium and poor crystal quality.

Boosting photocatalytic activity of single metal atom oxide anchored on TiO2 nanoparticles: An efficient catalyst for photodegradation of pharmaceutical pollutants

The distribution of active sites across the surface of a catalyst can help alleviate issues with mass transfer and improve atom economy. To create such a precise catalyst, this work reports the high loading of a single metal (tungsten/nickel) atom oxide anchored on the surface of TiO2 nanoparticles (WNiTiR) through a simple sonication method. According to aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), tungsten/nickel atoms are distributed uniformly over TiO2 and reduced graphene oxide (rGO). The photodegradation process was optimized by investigating the impact of different catalysts, dosage variations, and the pH of the reaction medium. Remarkably, the WNiTiR nanocomposites demonstrated increased photocatalytic activity by degrading over 97.15% of Ibuprofen (IBF) and 98.35% of Ciprofloxacin (CF) pollutants. The findings of the experiment on reactive oxygen species (ROS) showed that the predominant active species were superoxide radicals (O2•-). In addition, the WNiTiR nanocomposite displayed superior structural stability and reusability even after being put through six cycles of continuous use.