Coupling of BiOCl Ultrathin Nanosheets with Carbon Quantum Dots for Enhanced Photocatalytic Performance

Over the past few decades,photocatalysis technology has received extensive attention because of its potential to mitigate or solve energy and environmental pollution problems.Designing novel materials with outstanding photocatalytic activities has become a research hotspot in this field.In this study,we prepared a series of photocatalysts in which BiOCl nanosheets were modified with carbon quantum dots(CQDs)to form CQDs/BiOCl composites by using a simple solvothermal method.The photocatalytic performance of the resulting CQDs/BiOCl composite photocatalysts was assessed by rhodamine B and tetracycline degradation under visible-light irradiation.Compared with bare BiOCl,the photocatalytic activity of the CQDs/BiOCl composites was significantly enhanced,and the 5 wt%CQDs/BiOCl composite exhibited the highest photocatalytic activity with a degradation efficiency of 94.5%after 30 min of irradiation.Moreover,photocatalytic N_(2)reduction performance was significantly improved after introducing CQDs.The 5 wt%CQDs/BiOCl composite displayed the highest photocatalytic N_(2)reduction performance to yield NH_3(346.25μmol/(g h)),which is significantly higher than those of 3 wt%CQDs/BiOCl(256.04μmol/(g h)),7 wt%CQDs/BiOCl(254.07μmol/(g h)),and bare BiOCl(240.19μmol/(g h)).Our systematic characterizations revealed that the key role of CQDs in improving photocatalytic performance is due to their increased light harvesting capacity,remarkable electron transfer ability,and higher photocatalytic activity sites.

Support effect of the supported ceria-based catalysts during NH_3-SCR reaction

To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2/γ‐Al2O3,CeO2/ZrO2,and CeO2/TiO2catalysts were prepared.The physicochemical properties were probed by means of X‐ray diffraction,Raman spectroscopy,Brunauer‐Emmett‐Teller surface area measurements,X‐ray photoelectron spectroscopy,H2‐temperature programmed reduction,and NH3‐temperature programmed desorption.Furthermore,the supported ceria‐based catalysts'catalytic performance and H2O+SO2tolerance were evaluated by the NH3‐SCR model reaction.The results indicate that out of the supported ceria‐based catalysts studied,the CeO2/γ‐Al2O3catalyst exhibits the highest catalytic activity as a result of having a high relative Ce3+/Ce4+ratio,optimum reduction behavior,and the largest total acid site concentration.Finally,the CeO2/γ‐Al2O3catalyst also presents excellent H2O+SO2tolerance during the NH3‐SCR process.

Tuning the local coordination environment of silver(Ⅰ) coordination networks with counterions for enhanced electrocatalytic CO_(2) reduction

Very recently, the local coordination environment of active sites has been found to strongly influence their performance in electrocatalytic CO_(2) reduction by tuning the intrinsic kinetics of CO_(2) activation and intermediate stabilization. It is imperative to elucidate the mechanism for such an influence towards the rational design of efficient catalysts;however, the complex interactions between the multiple factors involved in the system make it challenging to establish a clear structure–performance relationship. In this work, we chose ion-intercalated silver(I)-based coordination networks(AgCNs) with a well-defined structure as a model platform, which enables us to understand the regulation mechanism of counterions as the counterions are the only tuning factor involved in such a system. We prepared two isostructural Ag CNs with different intercalation ions or counterions of BF_(4)^(-) and ClO_(4)^(-)(named as AgCNs-BF_(4) and AgCNs-ClO_(4)) and found that the former has a more competitive CO_(2) electroreduction performance than the latter. AgCNs-BF_(4) achieves the highest Faradaic efficiency for CO_(2) to CO of 87.1% at-1.0 V(vs. RHE) with a higher partial current density, while AgCNs-ClO_(4) exhibits only 77.2% at the same applied potential.Spectroscopic characterizations and theoretical calculation reveal that the presence of BF_(4)^(-)is more favorable for stabilizing the COOH^(*) intermediate by weakening hydrogen bonds, which accounts for the superior activity of Ag CNs-BF_(4).

Appropriate supply of irrigation and nitrogen produced higher yields of cherry tomatoes

Accurate irrigation and nitrogen application are essential for promoting the growth and yield of cherry tomatoes.In investigating the effects of irrigation and nitrogen on the growth,photosynthesis,and yield of cherry tomatoes,nine treatments including three levels of both irrigation and nitrogen were conducted over two growing seasons.Transverse stem diameter and horizontal stem diameter had the best performance at the irrigation level of 75%evaporation(E_(p)),although their responses to nitrogen were different for the two years.Plant height increased with the increase of irrigation and nitrogen.Plant dry matter(PDM)was significantly affected by irrigation and nitrogen interaction.The lowest PDM was found in the highest proportion of root dry matter,which occurred under low nitrogen level.The net photosynthetic rate(Pn)and transpiration rate enhanced with the increase of irrigation.Medium nitrogen showed promotion effect on all photosynthetic parameters in both growing seasons.Six of all fourteen indicators showed significant correlations with yield.Especially,single plant fruit number and PDM in 2018 Fall had significant positive direct effects on yield with the path coefficients of 0.648 and 1.159,while the significant direct path coefficients were 0.362 and 0.294 in Fruit dry matter and Pn for 2019 Spring,respectively.Based on the comprehensive evaluation of growth and yield by TOPSIS,the irrigation level of 75%E_(p) combined with medium nitrogen application produced higher yields by promoting the growth and photosynthesis of cherry tomatoes.It provides a strategy for water and nitrogen management of cherry tomatoes in Northwest China.

Bridging molecular photosensitizer and catalyst on carbon nanotubes toward enhanced selectivity and durability for CO_(2)photoreduction

Homogenous molecular photocatalysts for CO_(2)reduction,especially metal complex-based photosensitizer-catalyst assemblages,have been attracting extensive research interests due to their efficiency and customizability.However,their low durability and recyclability limit practical applications.In this work,we immobilized the catalysts of metal terpyridyl complexes and the photosensitizer of[Ru(bpy)3]Cl2onto the surface of carbon nanotubes through covalent bonds and electrostatic interactions,respectively,transforming the homogeneous system into a heterogeneous one.Our characterizations prove that these metal complexes are well dispersed on CNTs with a high loading(ca.12 wt.%).Photocatalytic measurements reveal that catalytic activity is remarkably enhanced when the molecular catalysts are anchored,which is three times higher than that of homogeneous molecular catalysts.Moreover,when the photosensitizer of[Ru(bpy)3]Cl2is immobilized,the side reaction of hydrogen evolution is completely suppressed and the selectivity for CO production reaches 100%,with its durability also significantly improved.This work provides an effective pathway for constructing heterogeneous photocatalysts based on rational assembly of efficient molecular photosensitizers and catalysts.

Function-switchable metal/semiconductor junction enables efficient photocatalytic overall water splitting with selective water oxidation products

A novel metal/semiconductor photocatalyst,Cu nanoparticles(NPs)modified TiO2 hollow spheres(Cu/TiO2),was designed for efficient photocatalytic overall water splitting(POWS)under both ultraviolet(UV)and visible(Vis)light.This Cu/TiO2 photocatalyst possesses excellent POWS performance under Vis light at the highest level among the reported TiO2-based photocatalysts.Interestingly,the metal/semiconductor junction formed between Cu and TiO2 enables controlled water-oxidation product selectivity(H2O2 or O2)via different reaction pathways regulated by irradiation wavelengths.Under UV light,the electrons excited in TiO2 are captured by Cu NPs through the Cu/TiO2 Schottky interface for H2 production,with the photoholes in TiO2 producing H2O2 through a two-electron process;whilst under Vis light,Cu NPs act as plasmon to inject hot electrons to TiO2 for H2 production,while O2 is produced by hot holes on Cu NPs via a four-electron process.This rational design of function-switchable metal/semiconductor junction may be helpful to understand the mechanisms for POWS with desired gas/liquid water-oxidation products.

Comprehensive analyses for genetic diversities of 19 autosomal STRs in Chinese Kazak group and its phylogenetic relationships with other continental populations

Short tandem repeats(STRs)play an essential role in forensic genetics due to their high degree of polymorphisms,wide distributions and easy detection method.In this study,allelic frequencies and forensic statistical parameters of the 19 autosomal STR loci in a Kazak ethnic group were calculated,and its genetic relationships with reference populations were assessed in order to understand population structure better and enrich population genetic data for forensic practice in Chinese Kazak ethnic group.There were 226 identified alleles with the corresponding allelic frequencies ranging from 0.0008 to 0.5295 in the 628 unrelated healthy Kazak individuals in Xinjiang Uygur Autonomous Region.All autosomal STRs were conformed to the Hardy-Weinberg equilibrium after Bonferroni’s correction.The cumulative power of discrimination and the combined probability of exclusion of all the 19 autosomal STRs were 0.999999999999999999999997162 and 0.999999994484,respectively.Furthermore,the DA distances and Fixation index values of pairwise populations,principal component analysis,multidimensional scaling analysis,phylogenetic tree analysis and structure analysis were conducted to probe the genetic relationships between the Kazak group and other reference populations.The population genetic results showed that these 19 autosomal STR loci were characterised by high genetic diversities in the Kazak group.Furthermore,the studied Kazak group had close genetic relationships with the Uyghur group and the Uzbek group.The present results may facilitate understanding the genetic background of the Chinese Xinjiang Kazak group.

Highly Efficient and Selective Photocatalytic Nonoxidative Coupling of Methane to Ethylene over Pd-Zn Synergistic Catalytic Sites

Photocatalytic nonoxidative coupling of CH_(4)to multicarbon(C^(2+))hydrocarbons(e.g.,C,H4)and H,under ambient conditions provides a promising energy-conserving approach for utilization of carbon resource.However,as the methyl intermediates prefer to undergo self-coupling to produce ethane,it is a challenging task to control the selective conversion of CH to higher valueadded CH4.Herein,we adopt a synergistic catalysis strategy by integrating Pd-Zn active sites on visible light-responsive defective WO_(3)nanosheets for synergizing the adsorption,activation,and dehydrogenation processes in CH_(4)to C_(2)H_(4)conversion.Benefiting from the synergy,our model catalyst achieves a remarkable C^(2+)compounds yield of 31.85μmolgh with an exceptionally high C,H4 selectivity of 75.3%and a stoichiometric H_(2)evolution.In situ spectroscopic studies reveal that the Zn sites promote the adsorption and activation of CH_(4)molecules to generate methyl and methoxy intermediates with the assistance of lattice oxygen,while the Pd sites facilitate the dehydrogenation of methoxy to methylene radicals for producing C_(2)H_(4)and suppress overoxidation.This work demonstrates a strategy for designing efficient photocatalysts toward selective coupling of CH_(4)to higher value-added chemicals and highlights the importance of synergistic active sites to the synergy of key steps in catalytic reactions.