Dominant Site Research Articles

Enzymatic characterization and dominant sites of foot-and-mouth disease virus 2C protein

Foot-and-mouth disease virus (FMDV) 2C protein is a conserved non-structural protein and crucial for replication of the virus. In this study, FMDV 2C protein was prepared and the enzymatic activities were investigated in detail. The protein could digest ssDNA or ssRNA into a small fragment at about 10 nt, indicating that the protein has nuclease activity. But it did not show digestion to blunt-end dsDNA or dsRNA. The nuclease activity of 2C protein could be inhibited in 2 mM Zn2+ or Ca2+ while enhanced by Mg2+ or Mn2+. FMDV 2C protein exhibited unwinding activity to all the three kinds of dsDNA and dsRNA (5′ protruded, 3′ protruded, and blunt-end). The unwinding velocity to 5′ protruded dsRNA was higher than to the blunt-end dsRNA. 2C protein only showed unwinding activity in high concentration of Mg2+, but no unwinding activity in physiological concentrations of Mg2+ and Ca2+, as well as in cell lysate. The 2C protein could catalyze two structured ssRNA to form double strand, thus it was proved to have RNA chaperone activity. The Mg2+ and ATP in different concentrations did not show promotion to the RNA chaperone activity. Finally, six mutant proteins (K116A, D160A, D170A, N207A, R226A, and F316A) were constructed and the enzymatic activities were analyzed. All the six mutations reduced the ATPase activity, D170A and F361A could inactivate the nuclease activity, while the N207A and F316A could inactivate the helicase activity. Our study provides a comprehensive understanding of the enzymatic activities of FMDV 2C protein.

Ultrafast Fenton-like reaction using a peroxymonosulfate-mediated confined-Fe0 catalyst for the degradation of sulfamethoxazole

Herein, a nanoconfinement strategy was employed to encapsulate nano zero-valent iron (confined-Fe0) for the rapid degradation of sulfamethoxazole (SMX) through a peroxymonosulfate (PMS)-mediated Fenton-like reaction. The confined-Fe0 catalyst was synthesized in situ using a liquid-phase reduction method, incorporating nitrilotriacetic acid (NA) modified carboxylated carbon nanotube (FOC-N-6). Comprehensive experimental analyses and characterizations demonstrated the FOC-N-6 catalyst facilitated rapid electron transfer through the carbon framework and the surface PMS reactive complex (FOC-N-6-PMS*). This process accelerated the Fe(III)/Fe(II) redox cycle and promoted the formation of surface Fe(II) active sites (Fe0-OCNT-COOFe(II)-), which served as dominant adsorption sites for PMS. Density functional theory (DFT) calculations revealed that the confined-Fe0 structure can decrease the adsorption energy (Eads) of PMS on the FOC-N-6 surface. And the FOC-N-6-PMS* facilitated the rapid degradation of SMX through both non-radical and radical pathways. This confined-Fe0 catalytic strategy holds promise as a viable method for controlling emerging contaminants.

Arabidopsis and maize terminator strength is determined by GC content, polyadenylation motifs and cleavage probability

The 3’ end of a gene, often called a terminator, modulates mRNA stability, localization, translation, and polyadenylation. Here, we adapted Plant STARR-seq, a massively parallel reporter assay, to measure the activity of over 50,000 terminators from the plants Arabidopsis thaliana and Zea mays. We characterize thousands of plant terminators, including many that outperform bacterial terminators commonly used in plants. Terminator activity is species-specific, differing in tobacco leaf and maize protoplast assays. While recapitulating known biology, our results reveal the relative contributions of polyadenylation motifs to terminator strength. We built a computational model to predict terminator strength and used it to conduct in silico evolution that generated optimized synthetic terminators. Additionally, we discover alternative polyadenylation sites across tens of thousands of terminators; however, the strongest terminators tend to have a dominant cleavage site. Our results establish features of plant terminator function and identify strong naturally occurring and synthetic terminators.

Mechanism of 7H-Dibenzo[c,g]carbazole metabolism in cytochrome P450 1A1: Insights from computational studies

7H-Dibenzo[c,g]carbazole (DBC) is a prevalent environmental contaminant that induces tumorigenesis in several experimental animals. Recently, it has been utilized to develop high-performance solar cells and organic phosphorescent materials. It is imperative to strengthen investigations of DBC metabolism to understand its potential risks to human health. In this study, human CYP1A1 was employed as the metabolic enzyme to investigate the metabolic mechanism of DBC by molecular docking, molecular dynamics (MD) simulation, and quantum mechanical (QM) calculation. The results indicate that DBC binds to CYP1A1 in two modes (mode 1 and mode 2) mainly through nonpolar solvation energies (ΔGnonpolar). The formation of the two binding modes is attributed to the anchoring effect of the hydrogen bond formed by DBC with Asp320 (mode 1) or Ser116 (mode 2). Mode 1 is a "reactive" conformation, while mode 2 is not considered a "reactive" conformation. C5 is identified as the dominant site, and the pyrrole nitrogen cannot participate in the metabolism. DBC is metabolized mainly by a distinct electrophilic addition-rearrangement mechanism, with an energy barrier of 21.74 kcal/mol. The results provide meaningful insights into the biometabolic process of DBC and contribute to understanding its environmental effects and health risks.

Peracetic acid activation by natural magnetite for bisphenol A degradation: Performance and degradation mechanism

Advanced oxidation processes based on activated peracetic acid (PAA) have been widely used in water treatment. In this study, magnetite was first employed in PAA activation for Bisphenol A (BPA) degradation. The results showed that the magnetic/PAA system degraded 94.6 % BPA in 60 min at neutral pH (pH = 6.7), exhibiting a higher rate constant (kobs = 0.051 min−1) than PAA or magnetite alone. X-ray photoelectron spectroscopy (XPS) results proved that ≡Fe(II) and surface hydroxyl group (OOH) were the dominant active sites, which promoted the electron transfer between magnetite, PAA, and BPA. According to the scavenging experiments and electron paramagnetic resonance (EPR) spectrum, the main reactive oxygen species responsible for BPA degradation include organic radicals (CH3COOO), Hydroxyl radical (OH) and singlet oxygen (1O2). The BPA degradation pathway was determined by LC-MS analysis, and the toxicity of the intermediates was evaluated by ECOSAR and wheat seed growth inhibition experiment. In addition, the magnetite/PAA system presented a good adaptability under a wide initial pH range, demonstrating efficient degradation even in the presence of complex matrices such as Cl−, NO3− or humic acid in water bodies while HCO3− and H2PO4− inhibited BPA degradation. This study not only reveals the mechanism of magnetite activating PAA but also provides a new idea for applying magnetite in PAA-based AOPs to remove micropollutants in wastewater.

Rethinking Productivity Evaluation in Precision Forestry through Dominant Height and Site Index Measurements Using Aerial Laser Scanning LiDAR Data

Rethinking Productivity Evaluation in Precision Forestry through Dominant Height and Site Index Measurements Using Aerial Laser Scanning LiDAR Data

Spatiotemporal stability of digital twin-guided atrial fibrillation dominant frequency sites and the clinical outcome of catheter ablation

Abstract Background Although the dominant frequency (DF) may localize the reentrant drivers of atrial fibrillation (AF), its meandering nature makes it difficult to localize as an extra-pulmonary vein (extra-PV) target. Purpose We explored and quantified the spatiotemporal stability of DF by sophisticated digital-twin maps and the association with the rhythm outcome of clinical AF catheter ablation (AFCA). Methods We retrospectively examined the DF sites in the digital twin integrated by high-density electroanatomical maps (EAM) of 170 patients previously included in the CUVIA-AF2 trial (male 70.6%, 59.2±11.3 years old, 100% persistent AF). We monitored 34 seconds of virtual AF and analyzed DF sites in 10 different left atrial (LA) regions at 3 consecutive periods (6 seconds each after 16sec induction and blanking periods). The spatiotemporal stability index (STSI) was calculated to quantify mean DF's spatial and temporal variability. During protocol-based rhythm follow-up, we assessed the atrial arrhythmia recurrence rate by dividing patients into two groups based on STSI 0.75. Results During the simulation, 108 out of 170 (63.5%) patients obtained mean DF values in all three consecutive periods. There were 26 (24.1%) patients in the stable DF group (STSI ≥0.75, Stable group) and 82 (75.9%) patients in the unstable DF group (STSI <0.75, Unstable group). Although the proportion of patients with hypertension (73.1 vs. 47.6%, p=0.041) was higher and left ventricular end-diastole diameter (51.3±3.9 vs. 49.0±4.4 mm, p=0.020) was larger in the stable DF group than in the unstable DF group, other parameters, including LA size, LA voltage, or AF ablation targets, did not differ between two groups. During the median 19 [15-22] months follow-up, the atrial arrhythmia recurrence rate of the Stable group is higher than that of the Unstable group (log-rank p=0.031, HR = 2.06, CI [1.06-4.01]) Conclusions We found that the temporally stable DF in EAM-integrated virtual AF, the potential extra-PV AF drivers, is a surrogate marker of the adverse rhythm outcome of AFCA. A prospective clinical trial targeting the spatiotemporally stable DF will be warranted.

Selective adsorption and separation of salicylic acid and 4‐hydroxyisophthalic acid from industry‐grade 4‐hydroxybenzoic acid on UiO‐66

AbstractIn this study, UiO‐66 was employed for the first time as an adsorbent to separate phenolic acid analogues, specifically 4‐hydroxyisophthalic acid and salicylic acid, from impurities. Synthesized in‐house, UiO‐66 was shown to exhibit high selectivity towards 4‐HIPA/4‐HBA and SA/4‐HBA when a molar equivalent of acetic acid modulator to terephthalic acid was set at 44. The adsorption capacities for 4‐HBA, 4‐HIPA, and SA were determined to be 56.34, 55.02, and 60.34 mg/g, respectively. Furthermore, it was observed that after six regeneration cycles, the adsorption capacity for 4‐HBA remained nearly unchanged, whereas those for 4‐HIPA and SA decreased by 5.6% and 2.6%, respectively. FTIR and XPS analyses revealed that all three compounds were adsorbed at the same dominant Zr cluster site on UiO‐66, primarily through hydrogen bonding and electrostatic interaction. Dynamic adsorption experiments revealed that 4‐HBA was the first to elute, maintaining the residual contents of 4‐HIPA and SA below 0.1 wt%. Compared to traditional separation techniques, this paper provided a simple and effective method to purify industrial grade 4‐hydroxybenzoic acid.

Unraveling the intrinsic activity origin of sludge-derived biochar for boosted chlorination of diclofenac: Key role of persistent free radicals

Economical and eco-friendly chlorine-based advanced oxidation processes (AOPs) have been urgently demanded to enhance the green abatement of emerging micropollutants. Herein, sludge-derived biochar (SBC) was innovatively introduced to activate free available chlorine (FAC) to enhance the elimination of diclofenac (DCF) among pH 5.0–11.0. Pyrolysis of municipal sludge endowed biochar with superior structure, various chemical compositions, and electronic properties, among which carbon-centered persistent free radicals (PFRs) were verified as the dominant active sites for enhanced chlorination based on correlation analysis. Electron spin resonance and electrochemical tests firstly verified that PFRs could mediate electron transfer toward FAC and dissolved oxygen to generate multiple reactive species of •OH, ClO•, 1O2, and O2•−. Further investigation revealed that enhanced DCF chlorination relied on both radical attack by •OH, ClO•, O2•− and direct electron transfer. Meanwhile, the regeneration of PFRs mediated by FAC and electron-rich DCF greatly promoted the reusability of SBC800. SBC800/FAC system was much superior to sole chlorination in terms of toxicity reduction and anti-interference capacity. This study innovatively introduced SBC as a green and sustainable catalyst to enhance chlorination efficiency, and provided new insights into the activation potential and mechanism of PFRs for chlorination.

Theoretical evidence on pyridinic nitrogen in N, S-coordinated Co single atom catalyst as dominant active site promoting H2 cleavage, H diffusion, and hydrogenation activity

The limitation of isolated metal active sites in single atom catalysts (SAC) hinder their application in hydrogenation reactions, necessitating the creation of additional active site beyond the metal site. This study introduces pyridinic N and S atoms into the N/C sheet, optimally adjusting the local environment of the Co site. This adjustment synergistically enhances H2 activation, H diffusion, and promotes the hydrogenation of nitrobenzene into aniline. The sterically hindered Co acidic site and N basic site, known as frustrated Lewis pairs, in defect-containing Co-N3SN-def1 model cooperatively facilitate the highly efficient cleavage of the H2 molecule with a barrier of only 0.37 eV. The findings suggest that the pyridinic N site in the Co-N3SN-def1 model acts as a reservoir for *H, significantly contributing to the enhanced activity for the hydrogenation of nitrobenzene. The mechanism unveiled in this study offers valuable insights for designing efficient heterogeneous catalysts for target hydrogenation reactions.

Primary extranodal lymphoma: a report of six cases in a private cancer centre in Nigeria

Primary extra-nodal lymphoma (PENL) refers to lymphomas which present with disease in any organ or tissue other than lymph nodes or spleen. Symptoms at initial presentation are mainly from extra nodal involvement and after routine staging procedures, the extra nodal involvement remains the clinically dominant site of disease with little or no nodal disease [1, 2]. About 25–40% of lymphomas arise at extra nodal sites and with clinical presentation similar to solid tumors [3, 4] creating ambiguity in diagnosis and delays in treatment especially in resource poor settings. We report six cases of PENL seen at a private cancer centre in Lagos, Nigeria between 2021 and 2022. The age range was 32–95 years with five females and one male. Two patients were HIV positive. Five patients had initial symptoms of vague abdominal pain with one patient investigated multiple times for peptic ulcer disease. One patient presented with pathological fracture of left femur. Another patient had previously been diagnosed with an inoperable cholangiocarcinoma. All patients had non-Hodgkin’s lymphoma, DLBCL being most common (83.37%). Four patients started chemotherapy. All treated patients showed good outcomes with complete or good partial response highlighting the importance of accurate diagnosis. Initial histological diagnosis in most of the cases did not suggest lymphoma until immunohistochemistry (IHC) results were received. Cancer care in Nigeria is fraught with difficulties obtaining accurate diagnosis due in part to the limited availability of IHC and molecular testing facilities required to characterize the malignant cells leading to delays in treatment and poorer prognosis [6–8].

RuSe2 and CoSe2 Nanoparticles Incorporated Nitrogen-Doped Carbon as Efficient Trifunctional Electrocatalyst for Zinc-Air Batteries and Water Splitting.

The development of affordable, highly active, and stable trifunctional electrocatalysts is imperative for sustainable energy applications such as overall water splitting and rechargeable Zn-air battery. Herein, we report a composite electrocatalyst with RuSe2 and CoSe2 hybrid nanoparticles embedded in nitrogen-doped carbon (RuSe2CoSe2/NC) synthesized through a carbonization-adsorption-selenylation strategy. This electrocatalyst is a trifunctional electrocatalyst with excellent hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) activities. An in-depth study of the effect of Se on the electrocatalytic process was conducted. Notably, the incorporation of Se moderately adjusted electronic structure of Ru and Co, enhancing all three types of catalytic performance (HER, η10 = 31 mV; OER, η10 = 248 mV; ORR, E1/2 = 0.834 V) under alkaline condition with accelerated kinetics and improved stability. Density functional theory (DFT) calculation reveals that the (210) crystal facet of RuSe2 is the dominant HER active site as it exhibited the lowest ΔGH* value. The in situ Raman spectra unravel the evolution process of the local electronic environment of Co-Se and Ru-Se bonds, which synergistically promotes the formation of CoOOH as the active intermediate during the OER. The superior catalytic efficiency and remarkable durability of RuSe2CoSe2/NC as an electrode for water splitting and zinc-air battery devices demonstrate its great potential for energy storage and conversion devices.

The influence of in situ purification system on pathogen in the river fed by the drainage of sewage plant.

An in situ integrated system, consisting of ecological floating islands (EFI), ecological riverbeds (ER), and ecological filter dams (EFD), was built in a ditch only receiving the effluent of sewage plant; the effect of in situ technologies on the distribution of aquatic pathogen was investigated. The results showed the aquatic pathogen decreased along the ditch. Specifically, the relative abundance of Legionella, Aeromonas, and Acinetobacter decreased from 0.032, 0.035, and 0.26 to 0.026%, 0.012%, and 0.08%, respectively. Sedimentation, filtration, and sorption (provided by plant roots and biofilms on substrates) were principal processes for the removal. The nitrogen removal bacteria to prevent the potential risk of eutrophication were also evaluated. The EFI and ER were the dominant sites for Nitrosomonas (34.96%, 32.84%) and Nitrospira (35.74%, 54.73%) enrichment, while EFI and EFD facilitated the enrichment of denitrification bacteria. Notably, the relative abundance of endogenous denitrifiers (DNB-en) (including Dechloromonas at 9.72%, Thermomonas at 0.58%, and Saccharibacteria at 2.55%) exceeded those of exogenous denitrifiers (DNB-ex) (Thauera at 0.20%, Staphylococcus at 0.005%, and Rhodobacter at 0.27%). This study demonstrated that the in situ integrated system was effective in reducing the abundance of pathogens in the drainage channel, and the deficiency of DNB-ex and carbon sources made nitrate removal difficult.

Antimalarial drug resistance profiling of Plasmodium falciparum infections in India using Ion Torrent deep sequencing

IntroductionTracking the emergence and spread of antimalarial drug resistance is critical for supporting progress towards the control and eventual elimination of malaria in South Asia, especially India. Plasmodium falciparum has evolved resistance to virtually every antimalarial drug, and significant progress has been made to identify the molecular genetic mechanisms involved in the most common types of resistance.MethodsAn amplicon sequencing protocol was used for molecular surveillance of antimalarial drug resistance in a total of 158 patient isolates collected from December 2012 to September 2015 from three sites in south, west and east India: Tamil Nadu, Gujarat, and Odisha respectively. Five full length Plasmodium falciparum genes whose mutant proteins are implicated in antimalarial drug resistance were investigated: Pfcrt for chloroquine, Pfdhfr for pyrimethamine, Pfdhps for sulfadoxine, Pfk13 for artemisinin and Pfmdr1 for resistance to multiple antimalarial drugs.ResultsWe observed a high proportion of wild-type Pfcrt and Pfdhfr haplotypes from the P. falciparum-dominant site Rourkela, while mutant Pfcrt and Pfdhfr haplotypes were fixed at the P. vivax dominant sites Chennai and Nadiad. The wild-type Pfdhps haplotype was predominant across all study sites. We identified mutations in the propeller domain of Pfk13, although they are not associated with resistance to artemisinin. Finally, using samples taken from the same patient on day 2, day 7, and day 14 after artemisinin combination treatment, we were able to observe changes in allele frequency of drug resistance genes during the course of an infection.DiscussionThis is the first high-throughput deep sequencing study of five full-length P. falciparum genes in clinical isolates from three different study sites in India with varying transmission ecologies. Amplicon sequencing based on ion-torrent has the potential to track changes in the frequency of drug resistant alleles as a patient is undergoing drug therapy, and to identify new resistance mutations as they increase in frequency in the patient. This study showed possibility of whole gene sequencing, leads to in-depth molecular surveillance of multiple antimalarial resistant candidates and furthermore suggests investigations on reversal of resistant genotypes due to usage of artemisinin combination therapy in P. falciparum prevalent areas of the country.

Improving the removal efficiency of oxygenated volatile organic compounds by defective UiO-66 regulated with water

The purification of oxygenated volatile organic compounds VOCs (OVOCs), important precursors of ozone and particulate matters, has triggered intensive research interests. UiO-66 with high photocatalytic activity have shown great potential. However, the lack of active sites severely limited the trapping and degradation of OVOCs. Herein, reo-UiO-66 with increased specific surface area, hierarchical porous structure and tunable acidic/basic sites was synthesized by simply adding water as the modulator. XRD, TGA and FTIR results confirmed the formation of reo-defects, which significantly affected the surface hydrophilicity and active sites of UiO-66. The adsorption of Lewis acidic acetaldehyde was enhanced by 265 times with coordinative unsaturated Zr acting as the dominant adsorption sites. The degradation efficiency of typical OVOCs (acetaldehyde and acetone) increased from 0% and 25% to 50% and 73%, respectively. This work provided a facile method to modulate the micro-environment in MOFs for the efficient capture and catalytic purification of OVOCs.

Inversion of Asymmetric Vortex Vein Dilatation in Pachychoroid Spectrum Diseases

PurposeIntervortex venous anastomosis is widely recognized as compensating for vortex vein congestion in pachychoroid spectrum diseases. However, determining the blood flow direction within the compensated drainage route is often challenging. Herein, we investigated the morphological patterns of vortex veins in eyes showing retrograde pulsatile vortex venous flow. DesignRetrospective observational case series. Subjects689 consecutive eyes with treatment-naïve central serous chorioretinopathy, pachychoroid neovasculopathy, or polypoidal choroidal vasculopathy. MethodsWe reviewed the clinical records of patients with these pachychoroid spectrum diseases. Multimodal images including indocyanine green angiography (ICGA) and en face optical coherence tomography were analyzed. Main Outcome MeasuresIntervortex venous anastomosis between superotemporal and inferotemporal vortex veins and the dominant site of dilated temporal vortex veins were determined in the eyes with retrograde pulsatile vortex venous flow in the temporal vortex veins. Results22 eyes with retrograde pulsatile vortex venous flow in the temporal vortex veins were identified utilizing early-phase ICGA videos. In 9 eyes, retrograde pulsatile flow was detected in the superotemporal vortex veins which were connected to the inferotemporal vortex veins via intervortex venous anastomoses. Among these cases, contralateral inferotemporal vortex vein dilatation was dominant in 7 eyes (77.8%), while superotemporal and inferotemporal vortex veins were symmetrically dilated in the other 2 eyes (22.2%). On the other hand, in 13 eyes, the retrograde pulsatile flow was detected in the inferotemporal vortex veins which were linked to the superotemporal vortex veins via intervortex venous anastomoses. In these eyes, contralateral superotemporal vortex vein dilatation was dominant in 10 eyes (76.9%). Superotemporal and inferotemporal vortex veins were symmetrically dilated in 2 eyes (15.4%), while mainly inferotemporal vortex veins were dilated in 1 eye (7.7%). ConclusionsIn pachychoroid spectrum diseases, there are cases wherein congested venous blood might drain into the contralateral vortex veins via intervortex anastomoses. Overloaded contralateral vortex veins may, as a consequence, become more dilated than the primary congested vortex veins. Inversion of asymmetric vortex vein dilatation might thereby develop in pachychoroid spectrum diseases.

"Imagine a place:" Power and intimacy in fandoms on Discord

With over 300 million users, the voice, video, and text chat application Discord has been steadily emerging as a dominant site of fan communities and practices. As the platform continues to grow and to court audiences beyond the site's gaming origins, fans have flocked to the site. To critically consider how fandom has developed on Discord, we analyze how power structures and intimacies between and across fandoms are constructed across three levels on the platform. At the smallest scale, rules, roles, and fan practices within individual Discord servers afford the explicit hierarchization of fans and the regulation of fan discourses. Next, Discord's subscription services encourage economic and cultural competition across and between servers of the same fan text. Finally, fan practices and discourses stretch across the entire Discord platform, connecting seemingly disparate fandoms through a variety of fan activities. By examining how fan practices and the platform's affordances constitute power structures and intimacies across these three levels, we provide a primer on the affordances and critical sites of inquiry on the ever-expanding Discord platform.

Dynamic Reconstruction of Two-Dimensional Defective Bi Nanosheets for Efficient Electrocatalytic Urea Synthesis.

Catalyst surface dynamics drive the generation of active species for electrocatalytic reactions. Yet, the understanding of dominant site formation and reaction mechanisms is limited. In this study, we thoroughly investigate the dynamic reconstruction of two-dimensional defective Bi nanosheets from exfoliated Bi2Se3 nanosheets under electrochemical CO2 and nitrate (NO3 -) reduction conditions. The ultrathin Bi2Se3 nanosheets obtained by NaBH4-assisted cryo-mediated liquid-phase exfoliation are more easily reduced and reconstructed to Bi nanosheets with high-density grain boundaries (GBs; GB-rich Bi). The reconstructed GB-rich Bi catalyst affords a remarkable yield rate of 4.6 mmol h-1 mgcat. -1 and Faradaic efficiency of 32 % for urea production at -0.40 V vs. RHE. Notably, this yield rate is 2 and 8.2 times higher than those of the low-GB Bi and bulk Bi catalysts, respectively. Theoretical analysis demonstrates that the GB sites significantly reduce the *CO and *NH2 intermediate formation energy and C-N coupling energy barrier, enabling selective urea electrosynthesis on the GB-rich Bi catalyst. This work will trigger further research into the structure-activity interplay in dynamic processes using in situ techniques.

Dynamic Reconstruction of Two‐Dimensional Defective Bi Nanosheets for Efficient Electrocatalytic Urea Synthesis

AbstractAbstract:Catalyst surface dynamics drive the generation of active species for electrocatalytic reactions. Yet, the understanding of dominant site formation and reaction mechanisms is limited. In this study, we thoroughly investigate the dynamic reconstruction of two‐dimensional defective Bi nanosheets from exfoliated Bi2Se3 nanosheets under electrochemical CO2 and nitrate (NO3−) reduction conditions. The ultrathin Bi2Se3 nanosheets obtained by NaBH4‐assisted cryo‐mediated liquid‐phase exfoliation are more easily reduced and reconstructed to Bi nanosheets with high‐density grain boundaries (GBs; GB‐rich Bi). The reconstructed GB‐rich Bi catalyst affords a remarkable yield rate of 4.6 mmol h−1 mgcat.−1 and Faradaic efficiency of 32 % for urea production at −0.40 V vs. RHE. Notably, this yield rate is 2 and 8.2 times higher than those of the low‐GB Bi and bulk Bi catalysts, respectively. Theoretical analysis demonstrates that the GB sites significantly reduce the *CO and *NH2 intermediate formation energy and C−N coupling energy barrier, enabling selective urea electrosynthesis on the GB‐rich Bi catalyst. This work will trigger further research into the structure‐activity interplay in dynamic processes using in situ techniques.

The performance and mechanism of HCHO oxidation on Pd/SiO2 catalysts with different Pd particle sizes

In general, for Pd-based catalysts, the smaller the Pd particles on the catalysts are, the better the activity for HCHO oxidation; this has solely been ascribed to the high Pd dispersion on the catalysts’ surface. However, the Pd site effect on HCHO oxidation is still not clear. In this work, we regulated the proportions of different Pd sites on Pd/SiO2 catalysts by high-temperature treatment of the carriers. With the increase in treatment temperature, the dominant active sites on Pd particles changed from terraces to steps and finally to corner sites. The corner sites were found to be important for oxygen activation, which led to the HCHO catalytic oxidation performance increasing in the order Pd/SiO2, Pd/SiO2(500) and Pd/SiO2(800). It is worth noting that in the reaction pathway for HCHO oxidation, formate was the primary intermediate on the Pd/SiO2 catalyst. However, in addition to formate, CO species were also detected on the Pd/SiO2(500) and Pd/SiO2(800) catalysts. DFT results confirmed that the corner sites were more favorable for the HCHO → CHO → CO pathway, compared to the terrace sites. This work elucidates the effect of Pd sites on the HCHO oxidation mechanism over Pd/SiO2 catalysts, providing valuable insights for the design of highly active catalysts.