Correlating Structural Disorder in Metal (Oxy)hydroxides and Catalytic Activity in Electrocatalytic Oxygen Evolution.

Understanding the correlation between the structural evolution of electrocatalysts and their catalytic activity is both essential and challenging. In this study, we investigate this correlation in the context of the oxygen evolution reaction (OER) by examining the influence of structural disorder during and after dynamic structural evolution on the OER activity of Fe-Ni (oxy)hydroxide catalysts using operando X-ray absorption spectroscopy, alongside other experiments and theoretical calculations. The Debye-Waller factors obtained from extended X-ray absorption fine structure analyses reflect the degree of structural disorder and exhibit a robust correlation with the intrinsic OER activities of the electrocatalysts. The enhanced OER activity of in situ-generated metal (oxy)hydroxides derived from different pre-catalysts is linked to increased structural disorder, offering a promising approach for designing efficient OER electrocatalysts. This strategy may inspire similar investigations in related electrocatalytic energy-conversion systems.

Ultra-Highly Active Ni-Doped MOF-5 Heterogeneous Catalysts for Ethylene Dimerization.

Here, an ultra-highly active Ni-MOF-5 catalyst with high Ni loading for ethylene dimerization is reported. The Ni-MOF-5 catalysts are synthesized by a facile one-pot co-precipitation method at room temperature, where Ni2+ replaces Zn2+ in MOF-5. Unlike Zn2+ with tetrahedral coordination in MOF-5, Ni2+ is coordinated with extra solvent molecules except for four-oxygen from the framework. After removing coordinated solvent molecules, Ni-MOF-5 achieves an ethylene turnover frequency of 352 000 h-1 , corresponding to 9040 g of product per gram of catalyst per hour, at 35 °C and 50 bar, far exceeding the activities of all reported heterogeneous catalysts. The high Ni loading and full exposure structure account for the excellent catalytic performance. Isotope labeling experiments reveal that the catalytic process follows the Cossee-Arlman mechanism, rationalizing the high activity and selectivity of the catalyst. These results demonstrate that Ni-MOF-5 catalysts are very promising for industrial catalytic ethylene dimerization.

Density functional theory based computational investigations on the stability of highly active trimetallic PtPdCu nanoalloys for electrochemical oxygen reduction.

Activity, cost, and durability are the trinity of catalysis research for the electrochemical oxygen reduction reaction (ORR). While studies towards increasing activity and reducing cost of ORR catalysts have been carried out extensively, much effort is needed in durability investigation of highly active ORR catalysts. In this work, we examined the stability of a trimetallic PtPdCu catalyst that has demonstrated high activity and incredible durability during ORR using density functional theory (DFT) based computations. Specifically, we studied the processes of dissolution/deposition and diffusion between the surface and inner layer of Cu species of Pt20Pd20Cu60 catalysts at electrode potentials up to 1.2 V to understand their role towards stabilizing Pt20Pd20Cu60 catalysts. The results show there is a dynamic Cu surface composition range that is dictated by the interplay of the four processes, dissolution, deposition, diffusion from the surface to inner layer, and diffusion from the inner layer to the surface of Cu species, in the stability and observed oscillation of lattice constants of Cu-rich PtPdCu nanoalloys.

Dynamic Core-Shell and Alloy Structures of Multimetallic Nanomaterials and Their Catalytic Synergies.

ConspectusMultimetallic nanomaterials containing noble metals (NM) and non-noble 3d-transition metals (3d-TMs) exhibit unique catalytic properties as a result of the synergistic combination of NMs and 3d-TMs in the nanostructure. The exploration of such a synergy depends heavily on the understanding of the atomic-scale structural details of NMs and 3d-TMs in the nanomaterials. This has attracted a great deal of recent interest in the field of catalysis science, especially concerning the core-shell and alloy nanostructures. A rarely asked question of fundamental significance is how the core-shell and alloy structural arrangements of atoms in the multimetallic nanomaterials dynamically change under reaction conditions, including reaction temperature, surface adsorbate, chemical environment, applied electrochemical potential, etc. The dynamic evolution of the core-shell/alloy structures under the reaction conditions plays a crucial role in the catalytic performance of the multimetallic nanocatalysts.This Account focuses on the dynamic structure characteristics for several different types of composition-tunable alloy and core-shell nanomaterials, including phase-segregated, elemental-enriched, dynamically evolved, and structurally different core-shell structures. In addition to outlining core-shell/alloy structure formation via processes such as seed-mediated growth, thermochemical calcination, adsorbate-induced evolution, chemical dealloying, underpotential deposition/galvanic displacement, etc., this Account will highlight the progress in understanding the dynamic core-shell/alloy structures under chemical or catalytic reaction conditions, which has become an important focal point of the research fronts in catalysis and electrocatalysis. The employment of advanced techniques, especially in situ/operando synchrotron high-energy X-ray diffraction and pair distribution function analyses, has provided significant insights into the dynamic evolution processes of NM/3d-TM nanocatalysts under electrocatalytic or fuel cell operating conditions. Examples will highlight Pt- or Pd-based nanoparticles and nanowires alloyed with various 3d-TMs with a focus on their structural evolution under reaction conditions. While the dynamic process is complex, the ability to gain an insight into the evolution of core-shell and alloy structures under the catalytic reaction condition is essential for advancing the design of multimetallic nanocatalysts. This Account serves as a springboard from fundamental understanding of the core-shell and alloy structural dynamics to the various applications of nanostructured catalysts/electrocatalysts, especially in the fronts of energy and environmental sustainability.

Synergetic Cobalt-Copper-Based Bimetal-Organic Framework Nanoboxes toward Efficient Electrochemical Oxygen Evolution.

The development of efficient oxygen electrocatalysts and understanding their underlying catalytic mechanism are of significant importance for the high-performance energy conversion and storage technologies. Herein, we report novel CoCu-based bimetallic metal-organic framework nanoboxes (CoCu-MOF NBs) as promising catalysts toward efficient electrochemical oxygen evolution reaction (OER), fabricated via a successive cation and ligand exchange strategy. With the highly exposed bimetal centers and the well-designed architecture, the CoCu-MOF NBs show excellent OER activity and stability, with a small overpotential of 271 mV at 10 mA cm-2 and a high turnover frequency value of 0.326 s-1 at an overpotential of 300 mV. In combination of quasi in situ X-ray absorption fine structure spectroscopy and density-functional theory calculations, the post-formed CoCu-based oxyhydroxide analogue during OER is believed to account for the high OER activity of CoCu-MOF NBs, where the electronic synergy between Co and neighbouring Cu atoms promotes the O-O bond coupling toward fast OER kinetics.

Engineering Platinum-Cobalt Nano-alloys in Porous Nitrogen-Doped Carbon Nanotubes for Highly Efficient Electrocatalytic Hydrogen Evolution.

Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal-organic framework-assisted pyrolysis-replacement-reorganization approach is developed to obtain ultrafine Pt-Co alloy nanoparticles (sub-10 nm) attached on the inner and outer shells of porous nitrogen-doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt-Co nano-alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically-neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt3 Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media.

Trimetallic Spinel NiCo2-x Fex O4 Nanoboxes for Highly Efficient Electrocatalytic Oxygen Evolution.

The development of efficient and low-cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage devices. Here, we report an elaborate design and synthesis of porous Co-based trimetallic spinel oxide nanoboxes (NiCo2-x Fex O4 NBs) by a novel metal-organic framework engaged strategy, which involves chemical etching, cation exchange, and subsequent thermal oxidation processes. Owing to the structural and compositional advantages, the optimized trimetallic NiCo2-x Fex O4 NBs (x is about 0.117) deliver superior electrocatalytic performance for OER with an overpotential of 274 mV at 10 mA cm-2 , a small Tafel slope of 42 mV dec-1 , and good stability in alkaline electrolyte, which is much better than that of Co-based bi/monometallic spinel oxides and even commercial RuO2 .

Origin of High Activity and Durability of Twisty Nanowire Alloy Catalysts under Oxygen Reduction and Fuel Cell Operating Conditions.

The ability to control the surface composition and morphology of alloy catalysts is critical for achieving high activity and durability of catalysts for oxygen reduction reaction (ORR) and fuel cells. This report describes an efficient surfactant-free synthesis route for producing a twisty nanowire (TNW) shaped platinum-iron (PtFe) alloy catalyst (denoted as PtFe TNWs) with controllable bimetallic compositions. PtFe TNWs with an optimal initial composition of ∼24% Pt are shown to exhibit the highest mass activity (3.4 A/mgPt, ∼20 times higher than that of commercial Pt catalyst) and the highest durability (<2% loss of activity after 40 000 cycles and <30% loss after 120 000 cycles) among all PtFe-based nanocatalysts under ORR or fuel cell operating conditions reported so far. Using ex situ and in situ synchrotron X-ray diffraction coupled with atomic pair distribution function (PDF) analysis and 3D modeling, the PtFe TNWs are shown to exhibit mixed face-centered cubic (fcc)-body-centered cubic (bcc) alloy structure and a significant lattice strain. A striking finding is that the activity strongly depends on the composition of the as-synthesized catalysts and this dependence remains unchanged despite the evolution of the composition of the different catalysts and their lattice constants under ORR or fuel cell operating conditions. Notably, dealloying under fuel cell operating condition starts at phase-segregated domain sites leading to a final fcc alloy structure with subtle differences in surface morphology. Due to a subsequent realloying and the morphology of TNWs, the surface lattice strain observed with the as-synthesized catalysts is largely preserved. This strain and the particular facets exhibited by the TNWs are believed to be responsible for the observed activity and durability enhancements. These findings provide new insights into the correlation between the structure, activity, and durability of nanoalloy catalysts and are expected to energize the ongoing effort to develop highly active and durable low-Pt-content nanowire catalysts by controlling their alloy structure and morphology.

A comparative study of less invasive stabilization system and titanium elastic nailing for subtrochanteric femur fractures in older children.

The objective of this study was to compare prospectively the complications and the radiographic and clinical outcomes of reverse less invasive stabilization system (LISS) and titanium elastic nailing (TEN) for the treatment of subtrochanteric femur fractures in older children. From April 2004 to February 2012, 52 children aged from 10 to 15 years old with subtrochanteric fractures were included in this study. 26 patients were treated with reverse LISS (LISS group) and 26 children treated with titanium elastic nails (TEN group) respectively. Perioperative care was standardized. Surgical time, blood loss, length of hospitalization, hospital costs, fracture union time, full weight-bearing time and complications were analyzed. The radiologic results as well as hip functional outcomes were evaluated. The average follow-up time of LISS group was 36.5±9.3 months and TEN group was 40.2±10.6 months. No significant difference between these two groups was found in union time, full weight-bearing time and average length of hospitalization. However, the patients of LISS group had longer operation time (60.0±10.6 min vs. 40.5±7.4 min, p<0.01), more blood loss (130.0±45.0 ml vs. 15.5±10.2 ml, p<0.01), and more hospital costs (25000±700 RMB vs. 10800±500 RMB, p<0.01). The overall complication rate was significantly higher in the LISS group than in the TEN group (12/26 vs. 5/26, p=0.039). There was no significant difference between the two groups in terms of early and late radiological results. Using the Sanders score system, there were 13 excellent, 6 good and 7 fair results in the LISS group compared with 22 excellent and 4 good results in the TEN group. The excellent and good rate was significantly different between the two groups (p=0.010). Our results indicated that TEN fixation of subtrochanteric femur fractures in older children was associated with better function scores and a lower overall complication rate when compared with reverse LISS.

Chitosan-zinc chelate improves intestinal structure and mucosal function and decreases apoptosis in ileal mucosal epithelial cells in weaned pigs.

The present study was conducted to investigate the effects of chitosan (CS)-Zn on intestinal morphology, mucosal epithelial cell apoptosis and mucosal immune function in weanling pigs. A total of 150 weanling barrows with a body weight of 7.2 kg were randomly allocated into five groups. A basal diet without Zn supplementation was used as the control and other four groups were fed the control diet supplemented with 50 or 100 mg/kg of Zn as CS-Zn, 100 mg/kg of Zn as ZnSO4 and 3000 mg/kg of Zn as ZnO, respectively. The feeding trial lasted for 28 d. The results showed that serum diamine oxidase activities, d-lactate levels and endotoxin contents were lower in pigs fed dietary 100 mg/kg of Zn as CS-Zn or 3000 mg/kg of Zn as ZnO than in pigs fed the control or 100 mg Zn/kg as ZnSO4 diet. The ratios of the villus height:crypt depth of the duodenum, jejunum and ileum were higher in pigs that received 100 mg/kg of Zn as CS-Zn or a high level of Zn as ZnO than in pigs fed the control diet. Moreover, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL)-stained ileal epithelial cells were found in the control group, and apoptotic cells did not appear prominently in pigs that received the 100 mg/kg of CS-Zn or ZnO diet. Secretory IgA concentration in ileal mucus was increased in the dietary group that received 100 mg/kg of CS-Zn or ZnO. These results indicated that dietary 100 mg CS-Zn/kg had similar biological effects to dietary 3000 mg ZnO/kg on intestinal morphology, mucosal epithelial cell apoptosis and mucosal immune function.

Management of distal third tibial fractures: comparison of combined internal and external fixation with minimally invasive percutaneous plate osteosynthesis.

PURPOSE: The objective of this study was to compare combined internal and external fixation (CIEF) with minimally invasive percutaneous plate osteosynthesis (MIPPO) in the treatment of distal third tibial fractures, and explore the benefits and defects of these two techniques. METHODS: From April 2004 to February 2012, a total of 44 patients were randomised to operative stabilisation either by two closed titanium elastic nails combined with an external fixator (CIEF, 22) or by minimally invasive percutaneous osteosynthesis with a locking plate (MIPPO, 22). Pre-operative variables included the patients' age, sex, fracture side, cause of injury, Tscherne classification of soft tissue injury, fracture pattern, presence of open fracture and interval from injury to surgery. Peri-operative variables were the operating time and the radiation time. Postoperative variables were wound problems, bone union time, time of recovery to work, the functional American Orthopaedic Foot and Ankle surgery (AOFAS) score and removal of hardware. RESULTS: There was no significant difference in the time to union, the time of recovery to work, function, alignment and total AOFAS scores between the two groups (P = 0.704, 0.835, 0.551, 0.716 and 0.212, respectively). The mean operating time and radiation time were longer in the MIPPO group than in the CIEF group (85.3 ± 12.5 vs. 73.2 ± 12.0 minutes, P = 0.002, and 3.1 ± 1.5 vs. 2.1 ± 1.2 minutes, P = 0.019, respectively). Wound complications were more common in the MIPPO group (18.2% vs. 0% with CIEF, P = 0.105). There was a trend for patients with MIPPO to have a higher incidence of ankle pain (31.8% vs. 9.1% with CIEF, P = 0.135). Painful implants were removed in 31.8% of patients with MIPPO versus 9.1% with CIEF (P = 0.135). Of the 165 self-tapping locking screws of the locking plates seven (four patients) were removed with some difficulty because of stripping of the hexagonal recess. CONCLUSIONS: Our results indicated that both CIEF and MIPPO were all efficient methods for treating distal third tibial fractures. However, CIEF had the advantages of a shorter operating and radiation time, less wound complication and ankle pain, less secondary operations for implant removal and easier removal of the implants.

Comparison of efficacy between endoscope-assisted anterior cervical discectomy and fusion (ACDF) and open ACDF in the treatment of single-segment cervical spondylotic myelopathy.

BACKGROUND: In this study, we compared the clinical efficacy of endoscope-assisted anterior cervical discectomy and fusion (ACDF) with open ACDF in the treatment of single-segment cervical spondylotic myelopathy. METHODS: A retrospective analysis was performed on 52 patients with single-segment cervical spondylotic myelopathy between June 2021 and February 2022, including 33 males and 19 females, with a mean age of 58.42 ± 9.26) years. Among them, 28 patients were treated with endoscope-assisted ACDF (Group A), including 2 cases of C4/5 segment, 16 cases of C5/6 segment, and 10 cases of C6/7 segment; 24 patients were treated with open ACDF (Group B), including 4 cases of C4/5 segment, 11 cases of C5/6 segment, and 9 cases of C6/7 segment. The operation time, intraoperative blood loss, hospital stay, and complications were recorded and compared between the two groups. The Visual Analogue Scale (VAS) and the Japanese Orthopaedic Association (JOA) score were used for clinical evaluation during the follow-up in the 1st month and 3rd month after surgery, and at the final follow-up. RESULTS: The 52 patients were followed up on average for 13.04 months (12-17 months). The operation time in Group A and Group B was (105.18 + 8.66) minutes and (81.88 + 6.05) minutes, the intraoperative blood loss was (84.29 + 13.45) mL and (112.92 + 17.81) mL, and the hospital stay was (6.75 + 1.29) days and (7.63 + 1.41) days, respectively. The difference between the two groups was statistically significant (P < 0.05). The VAS and JOA scores in the 1st month and the 3rd month after surgery and the last follow-up significantly improved in both groups compared with those before surgery (P < 0.05). The VAS and JOA scores of Group A in the 1st month, 3rd month after surgery, and the last follow-up were better than those in Group B (P < 0.05). The complication rate in Group A was 7% (2/28), which was not significantly different from the 17% (4/24) in Group B (P > 0.05). CONCLUSION: Both endoscope-assisted ACDF and open ACDF can achieve satisfactory clinical efficacy in the treatment of single-segment cervical spondylotic myelopathy. Although the operation time of endoscope-assisted ACDF is prolonged, it has the advantages of clear vision, thorough decompression, less blood loss, and reduced risk of nerve damage, and is worthy of clinical promotion and application.

[Determination of 35 prohibited pesticide residues in Saussurea costus by modified QuEChERS method based on multi-walled carbon nanotubes coupled with gas chromatography-tandem mass spectrometry].

Saussurea costus, a perennial herb belonging to the Asteraceae family, is a vital ingredient in traditional Chinese medicine. Increased demands for the herb have led to its widespread cultivation in China, but the corresponding increase in pesticide use has raised concerns about pesticide residues. Such residues would affect the safety and global market potential of Saussurea costus. Thus, a simple method is crucial to detect pesticide residues. The QuEChERS technique, in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), is commonly used for residue detection. However, traditional adsorbents may be unable to purify complex herbal mixtures well, affecting accuracy and instrument performance. Choosing suitable purification materials for Saussurea costus samples with complex matrices is of significant importance. This study focused on the detection of 35 prohibited pesticides in Saussurea costus. A rapid detection method was established by combining the QuEChERS technique with GC-MS/MS and utilizing a combination of multiwalled carbon nanotubes (MWCNTs), octadecylsilane-bonded silica gel (C18), and anhydrous magnesium sulfate (MgSO4) as the purification adsorbent. The samples were extracted with acetonitrile, purified by an improved QuEChERS process, subjected to GC-MS/MS analysis in multiple reaction monitoring (MRM) mode, and quantified using the internal standard method. The purification effects of four materials (C18, MWCNTs, N-propyl ethylenediamine (PSA), and graphitized carbon black (GCB)) and their optimal dosages were investigated by considering the matrix characteristics of the samples. An orthogonal experimental design was employed to optimize the ratio of adsorbent combinations, and the optimal adsorbent combination was determined to be 450 mg of MgSO4, 400 mg of C18, and 50 mg of MWCNTs. Matrix effect (ME) evaluation of the S. costus matrix showed that 31 target compounds strongly exhibited matrix-enhancement effects. Thus, matrix-matched calibration was employed in this study. Methodological investigation revealed that the standard curves for the 35 pesticides exhibited good linearity, with correlation coefficients (r2) greater than 0.9970. The average recoveries at three spiked levels ranged from 69.6% to 126.9%, and the relative standard deviations (RSDs) for parallel groups were all less than 10%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.2 to 5.4 µg/kg and from 0.6 to 18.1 µg/kg, respectively. The developed method was used to screen and detect 35 pesticide residues in 20 batches of S. costus samples, and the target compounds were detected in six batches. The proposed method is simple, sensitive, and accurate. Thus, it is suitable for the rapid screening and detection of the 35 pesticide residues in S. costus and provides technical support for the cultivation, production, and quality control of the herb.

Iatrogenic flexor tendon rupture caused by misdiagnosing sarcoidosis-related flexor tendon contracture as tenosynovitis: A case report.

BACKGROUND: Sarcoidosis is a multisystem disease characterized by granuloma formation in various organs. Sarcoidosis-related flexor tendon contractures are uncommon in clinical settings. This contracture is similar to stenosing tenosynovitis and potentially leads to misdiagnosis and mistreatment. Herein, we report a rare case of sarcoidosis-related finger flexor tendon contracture that was misdiagnosed as tenosynovitis. CASE SUMMARY: A 44-year-old woman presented to our department with flexion contracture of the right ring and middle fingers. The patient was misdiagnosed with tenosynovitis and underwent acupotomy release of the A1 pulley of the middle finger in another hospital that resulted in iatrogenic rupture of both the superficial and profundus flexors. Radiological presentation showed multiple sarcoid involvements in the pulmonary locations and ipsilateral forearm. A diagnosis of sarcoidosis was made based on the presence of non-caseating granulomas with tubercles consisting of Langhans giant cells with lymphocyte infiltration on biopsy, and the patient underwent surgical repair for the contracture. After 2 mo, the patient experienced another spontaneous rupture of the repaired middle finger tendon and underwent surgical re-repair. Satisfactory results were achieved at the 10 mo follow-up after reoperation. CONCLUSION: Sarcoidosis-related finger contractures are rare; thus, caution should be exercised when dealing with such patients to avoid incorrect treatment.

Supporting Trimetallic Metal-Organic Frameworks on S/N-Doped Carbon Macroporous Fibers for Highly Efficient Electrocatalytic Oxygen Evolution.

Hybrid materials, integrating the merits of individual components, are ideal structures for efficient oxygen evolution reaction (OER). However, the rational construction of hybrid structures with decent physical/electrochemical properties is yet challenging. Herein, a promising OER electrocatalyst composed of trimetallic metal-organic frameworks supported over S/N-doped carbon macroporous fibers (S/N-CMF@Fex Coy Ni1-x-y -MOF) via a cation-exchange strategy is delicately fabricated. Benefiting from the trimetallic composition with improved intrinsic activity, hollow S/N-CMF matrix facilitating exposure of active sites, as well as their robust integration, the resultant S/N-CMF@Fex Coy Ni1-x-y -MOF electrocatalyst delivers outstanding activity and stability for alkaline OER. Specifically, it needs an overpotential of 296 mV to reach the benchmark current density of 10 mA cm-2 with a small Tafel slope of 53.5 mV dec-1 . In combination with X-ray absorption fine structure spectroscopy and density functional theory calculations, the post-formed Fe/Co-doped γ-NiOOH during the OER operation is revealed to account for the high OER performance of S/N-CMF@Fex Coy Ni1-x-y -MOF.

Atomically dispersed Ni activates adjacent Ce sites for enhanced electrocatalytic oxygen evolution activity.

Manipulating the intrinsic activity of heterogeneous catalysts at the atomic level is an effective strategy to improve the electrocatalytic performances but remains challenging. Here, atomically dispersed Ni anchored on CeO2 particles entrenched on peanut-shaped hollow nitrogen-doped carbon structures (a-Ni/CeO2@NC) is rationally designed and synthesized. The as-prepared a-Ni/CeO2@NC catalyst exhibits substantially boosted intrinsic activity and greatly reduced overpotential for the electrocatalytic oxygen evolution reaction. Experimental and theoretical results demonstrate that the decoration of isolated Ni species over the CeO2 induces electronic coupling and redistribution, thus resulting in the activation of the adjacent Ce sites around Ni atoms and greatly accelerated oxygen evolution kinetics. This work provides a promising strategy to explore the electronic regulation and intrinsic activity improvement at the atomic level, thereby improving the electrocatalytic activity.

[Effect of Coconut Fiber Biochar and Its Nitrate Modification on Pb Passivation in Paddy Soils].

The effects of coconut fiber biochar (CFB) and nitrate-modified coconut fiber biochar (NCFB) on the passivation of exogenous lead (Pb) in paddy soils and their underlying mechanisms were investigated using soil incubation experiments combined with spectroscopic techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray fluorescence (SRXRF), and Fourier transform infrared absorption spectroscopy (FTIR). The effects of NCFB and CFB on the passivation of exogenous lead (Pb) in paddy soils and its underlying mechanisms were investigated. Compared with that of CFB, the inner wall of NCFB honeycomb pores was rougher, and the amount of alcohol-phenol-ether functional groups containing the C-O structure and the amount of carboxyl groups containing the C[FY=,1]O/O[FY=,1]C-O structure on the surface of CFB was significantly decreased after nitric acid modification. Compared with that in the control (without biochar) paddy soil after 150 d of incubation, the EDTA-extracted Pb content in the paddy soil with CFB and NCFB was reduced by 39.7% and 105.4%, respectively. The carbonate-bound and Fe-Mn oxide-bound Pb contents were significantly lower, and the organic-bound and residue Pb contents were significantly higher in the NCFB-added soil. The SRXRF scans showed that the exogenous Pb was enriched in the microregions of CFB particles rich in Ca and Cu elements and relatively less so in the microregions of soil aggregates rich in the Fe, Mn, and Ti elements. In addition, the characteristic peaks of carboxylates (1384 cm-1) in A-CFBPb and A-NCFBPb were significantly enhanced in the incubation experiment in the presence of exogenous Pb compared to A-CFB and A-NCFB in the absence of exogenous Pb. The addition of CFB or NCFB was more effective in passivating exogenous Pb in paddy soils and promoted the gradual transformation of Pb from unstable to more stable forms in paddy soils to achieve the effect of passivating Pb. The greater amount of carboxyl functional groups in NCFB participated in the passivation of exogenous Pb, which made NCFB more effective than CFB in passivating Pb. NCFB was more effective than CFB in passivating exogenous Pb in paddy soils due to its rougher inner walls of honeycomb pores and abundant carboxyl functional groups. In tropical areas such as Hainan, coconut fiber biochar and its modification can be considered as an environmentally friendly candidate method for the remediation of soil Pb contamination.

Surface Modification of 2D Photocatalysts for Solar Energy Conversion.

2D materials show many particular properties, such as high surface-to-volume ratio, high anisotropic degree, and adjustable chemical functionality. These unique properties in 2D materials have sparked immense interest due to their applications in photocatalytic systems, resulting in significantly enhanced light capture, charge-transfer kinetics, and surface reaction. Herein, the research progress in 2D photocatalysts based on varied compositions and functions, followed by specific surface modification strategies, is introduced. Fundamental principles focusing on light harvesting, charge separation, and molecular adsorption/activation in the 2D-material-based photocatalytic system are systemically explored. The examples described here detail the use of 2D materials in various photocatalytic energy-conversion systems, including water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide production, and organic synthesis. Finally, by elaborating the challenges and possible solutions for developing these 2D materials, the review is expected to provide some inspiration for the future research of 2D materials used on efficient photocatalytic energy conversions.

A coupled study of ecological security and land use change based on GIS and entropy method-a typical region in Northwest China, Lanzhou.

Due to rapid population growth, industrialization, and urbanization, it is particularly important to address the increasingly serious ecological security issues in the process of urbanization, while it is important to grasp the impact of changes in land use structure on ecological security for scientific planning and to aid decision-making. As a typical valley basin industrialized city in northwest China, Lanzhou has complex geomorphology and climate with distinct regional characteristics, and the relationship between land use and ecological security is complex. In order to understand the current status and influencing factors of ecological security in various regions of Lanzhou, and to explore the intrinsic connection between ecological security and land use, this study constructed an ecological security evaluation index system based on the pressure-state-response (PSR) model with 14 secondary factors including natural, social, and economic factors. Based on the entropy method, GIS was used to analyze the trend of ecological security in each district and to clarify the coupling relationship between ecological security and land use change in Lanzhou City. The results show that the ecological security index (ESI) of Xigu District, a typical heavy industrial area, increased from 0.26 to 0.35, and the ESI of Yuzhong County, an agricultural development area, increased from 0.51 to 0.55 from 2000 to 2017. Low ESI was mainly distributed in areas with developed heavy industry, while high ESI was mainly found in areas with favorable natural conditions and mainly agricultural development. Economic factors were the leading factors affecting the ecological security of Lanzhou. In general, changes in land use structure and ecological security were inextricably linked, and the two influence and interact with each other. These results could provide some reference for the study of ecological security development and land use change in typical river valley cities and also provide a new path for other cities to study ecological security and the conservation of the ecological environment.

Lattice Strain and Surface Activity of Ternary Nanoalloys under the Propane Oxidation Condition.

The ability to harness the catalytic oxidation of hydrocarbons is critical for both clean energy production and air pollutant elimination, which requires a detailed understanding of the dynamic role of the nanophase structure and surface reactivity under the reaction conditions. We report here findings of an in situ/operando study of such details of a ternary nanoalloy under the propane oxidation condition using high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The catalysts are derived by alloying Pt with different combinations of second (Pd) and third (Ni) transition metals, showing a strong dependence of the catalytic activity on the Ni content. The evolution of the phase structure of the nanoalloy is characterized by HE-XRD/PDF probing of the lattice strain, whereas the surface activity is monitored by DRIFTS detection of the surface intermediate formation during the oxidation of propane by oxygen. The results reveal the dominance of the surface intermediate species featuring a lower degree of oxygenation upon the first C-C bond cleavage on the lower-Ni-content nanoalloy and a higher degree of oxygenation upon the second C-C bond cleavage on the higher-Ni-content nanoalloy. The face-centered-cubic-type phase structures of the nanoalloys under the oxidation condition are shown to exhibit Ni-content-dependent changes of lattice strains, featuring the strongest strain with little variation for the higher-Ni-content nanoalloy, in contrast to the weaker strains with oscillatory variation for the lower-Ni-content nanoalloys. This process is also accompanied by oxygenation of the metal components in the nanoalloy, showing a higher degree of oxygenation for the higher-Ni-content nanoalloy. These subtle differences in phase structure and surface activity changes correlate with the Ni-composition-dependent catalytic activity of the nanoalloys, which sheds a fresh light on the correlation between the dynamic change of atomic strains and the surface reactivity and has significant implications for the design of oxidation catalysts with enhanced activities.