Engineering the Coordination Sphere of Isolated Active Sites to Explore the Intrinsic Activity in Single-Atom Catalysts

Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinct catalytic performance.Through extensive research,it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors.In this review,we summarize a series of representative systems of single-atom catalysts,discussing their preparation,characterization,and structure-property relationship,with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities.We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis.With this article,we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.

Altered relationship between thickness and intrinsic activity amplitude in generalized tonic–clonic seizures

A thinner cortex has higher potential for binding GABA receptor A which is associated with larger amplitudes of intrinsic brain activity(i BA). However, the relationship between cortical thickness and i BA is unknown in intact and epileptic brains. To this end, we investigated the relationship between cortical thickness measured by highresolution MRI and surface-based i BA derived from resting-state functional MRI in normal controls(n = 82) andpatients with generalized tonic–clonic seizures(GTCS)only(n = 82). We demonstrated that the spatial distribution of cortical thickness negatively correlated with surface-based i BA amplitude at both whole-brain and within independent brain functional networks. In GTCS patients,spatial coupling between thickness and i BA amplitude decreased in the default mode, dorsal attention, and somatomotor networks. In addition, the vertex-wise acrosssubject thickness–i BA amplitude correspondence altered in the frontal and temporal lobes as well as in the precuneus in GTCS patients. The relationship between these two modalities can serve as a brain-based marker for detecting epileptogenic changes.

Regional homogeneity of intrinsic brain activity related to the main alexithymia dimensions

Background Alexithymia is a multidimensional personality construct.Objective This study aims to investigate the neuronal correlates of each alexithymia dimension by examining the regional homogeneity （ReHo） of intrinsic brain activity in a resting situation.Methods From university freshmen, students with alexithymia and non-alexithymia were recruited. Their alexithymic traits were assessed using the Toronto Alexithymia Scale-20. The ReHo was examined using a resting-state functional MRI approach.Results This study suggests signifcant group differences in ReHo in multiple brain regions distributed in the frontal lobe, parietal lobe, temporal lobe, occipital lobe and insular cortex. However, only the ReHo in the insula was positively associated with diffculty identifying feelings, a main dimension of alexithymia. The ReHo in the lingual gyrus, precentral gyrus and postcentral gyrus was？positively associated with diffculty describing feelings in？participants with？alexithymia. Lastly, the ReHo in the right dorsomedial prefrontal cortex （DMPFC_R） was negatively related to the externally oriented thinking style of participants with？alexithymia.Conclusion In conclusion, these results suggest that the main dimensions of alexithymia are correlated with specifc brain regions’ function, and the role of the insula, lingual gyrus, precentral gyrus, postcentral gyrus and DMPFC_R in the neuropathology of alexithymia should be further investigated.

Facile preparation and efficient MnxCoy porous nanosheets for the sustainable catalytic process of soot

The pursuit of high-performance is worth considerable effort in catalysis for energy efficiency and environmental sustainability. To develop redox catalysts with superior performance for soot combustion, a series of Mn_(x)Co_(y) oxides were synthesized using MgO template substitution.This method greatly improves the preparation and catalytic efficiency and is more in line with the current theme of green catalysts and sustainable development. The resulting Mn_(1)Co_(2.3) has a strong activation capability of gaseous oxygen due to a high concentration of Co^(3+) and Mn^(3+). The Mn doping enhanced the intrinsic activity by prompting oxygen vacancy formation and gaseous oxygen adsorption. The nanosheet morphology with abundant mesoporous significantly increased the solid–solid contact efficiency and improved the adsorption capability of gaseous reactants. The novel design of Mn_(1)Co_(2.3)oxide enhanced its catalytic performance through a synergistic effect of Mn doping and the porous nanosheet morphology, showing significant potential for the preparation of high-performance soot combustion catalysts.

Modification strategies on transition metal-based electrocatalysts for efficient water splitting

Electrocatalytic water splitting driven by electrocatalysts is recognized as a promising strategy to generate clean hydrogen fuel.Searching and constructing high-efficient and low-cost electrocatalysts is vital in the practical applications of electrocatalytic water splitting.Although transition metal-based materials have been considered as promising electrocatalysts,the satisfactory activities are usually not built on the bulk materials,but strongly relying on elaborately designing these electrocatalysts.Herein,the recent theoretical and experimental progress on modification strategies to improve the intrinsic activities is summarized,especially including element doping,phase engineering,structure cooperation,interface engineering,vacancy engineering,strain engineering and self-functionalization.Finally,the future opportunities and challenges on these modification strategies are also proposed.Overall,it is anticipated that these modification strategies offer some new understandings on rationally constructing non-noble electrocatalysts for efficient electrocatalytic water splitting.

Origin of Bismuth-Rich Strategy in Bismuth Oxyhalide Photocatalysts

Recently,the bismuth-rich strategy via increasing the bismuth content has been becoming one of the most appealing approaches to improve the photocatalytic performance of bismuth oxyhalides.However,insights into the mechanism behind the encouraging experiments are missing.Herein,we report the results of the theory-led comprehensive picture of bismuth-rich strategy in bismuth oxyhalide photocatalysts,selecting Bi_(5)O_(7)X(X=F,Cl,Br,I)as a prototype.First-principle calculations revealed that the strategy enables good n-type conductivity,large intrinsic internal electric field,high photoreduction ability and outstanding harvest of visible light,and particularly ranked the intrinsic activity of this family:Bi_(5)O_(7)F>Bi_(5)O_(7)I>Bi_(5)O_(7)Br>Bi_(5)O_(7)Cl.Designed experiments confirmed the theoretical predictions,and together,these results are expected to aid future development of advanced photocatalysts.

Electrochemical partial reduction of Ni(OH)_(2) to Ni(OH)_(2)/Ni via coupled oxidation of an interfacing NiAl intermetallic compound for robust hydrogen evolution

Ni-based porous electrocatalysts have been widely used in the hydrogen evolution reaction(HER)in alkaline water electrolysis,and the catalysts are produced by selective leaching of Al from Ni-Al alloys.It is well known that chemical leaching of Ni-Al intermetallic compound(IMC)generates a high surface area in Ni(OH)_(2).However,the Ni(OH)_(2) produced by leaching the Ni-Al intermetallic compound retards the hydrogen evolution reaction,which is attributed to its weak hydrogen adsorption energy.In this study,we controlled the chemical state of Ni using plasma vapor deposition(PVD)followed by heat treatment,selective Al leaching,and electrochemical reduction.X-ray diffraction(XRD),scanning microscopy(SEM),transmission electron microscopy(TEM),and energy-dispersive X-ray spectroscopy(EDS)were used to confirm the phase evolution of the electrocatalysts during fabrication.We reveal that the heat-treated Ni-Al alloy with a thick Ni2Al3surface layer underwent selective Al leaching and produced biphasic interfaces comprising Ni(OH)_(2) and NiAl IMCs at the edges of the grains in the outermost surface layer.Coupled oxidation of the interfacing NiAl IMCs facilitated the partial reduction of Ni(OH)_(2) to Ni(OH)_(2)/Ni in the grains during electrochemical reduction,as confirmed by X-ray photoelectron spectroscopy(XPS).An electrocatalyst containing partially reduced Ni(OH)_(2)/Ni exhibited an overpotential of 54 mV at 10 mA/cm^(2) in a half-cell measurement,and a cell voltage of 1.675 V at 0.4 A/cm2for single-cell operation.A combined experimental and theoretical study(density functional theory calculations)revealed that the superior HER activity was attributed to the presence of partially reduced metallic Ni with various defects and residual Al,which facilitated water adsorption,dissociation,and finally hydrogen evolution.

Subsurface intercalation activating basal plane of black phosphorus for nitrogen reduction

Ammonia(NH3)is not only an important chemical in many fields,but also provides a promising intermediate for energy stor-age[1,2].To produce NH3 from naturally abundant N2,the strong N≡N bond in the inert N2 molecules must be broken firstly.

Unravelling the role of boron dopant in borocarbonitirde catalytic dehydrogenation reaction

Borocarbonitride(BCN) materials are newly developed metal-free catalytic materials exhibiting high selectivity in oxidative dehydrogenation(ODH) of alkanes. However, the in-depth understandings on the role of boron(B) dopants and the intrinsic activities of –C=O and –B–OH still remain unknown.Herein, we report a series of BCN materials with regulable B content and surface oxygen functional groups via self-assembly and pyrolysis of guanine and boric acid. We found that the B/C ratio is the key parameter to determine the activity of ODH and product distribution. Among them, the high ethylbenzene conversion(~57%) and styrene selectivity(~83%) are achieved in ODH for B_(1)CN. The styrene selectivity can be improved by increasing of B/C ratio and this value reaches near 100% for B_5CN.Structural characterizations and kinetic measurements indicate that –C=O and –B–OH dual sites on BCN are real active sites of ODH reaction. The intrinsic activity of –C=O(5.556 × 10^(-4)s^(-1)) is found to be 23.7 times higher than –B–OH(0.234 × 10^(-4)s^(-1)) site. More importantly, we reveal that the deep oxidation to undesirable CO_(2) occurs on –C=O rather than –B–OH site, and B dopant in BCN materials can reduce the nucleophilicity of –C=O site to eliminate the CO_(2) emission. Overall, the present work provides a new insight on the structure–function relationship of the BCN catalytic systems.

Intrinsic electrochemical activity modulation of MOF-derived C/N-NiCoMn-LDH/Ag electrode for low temperature hybrid supercapacitors

Layered double hydroxides(LDHs)are promising electrode candidates for supercapacitors.However,lim-itations like inferior cycling stability and unsatisfactory charge storage capability at low temperatures have exerted negative effects on their applications.Herein,a novel synthetic process has been elaborately designed and provided to have the composition and structure of the C/N-NiCoMn-LDH/Ag(C/N-CNMA)delicately regulated.Both the experimental and theoretical researches unveil that the incorporated manganese species and elemental silver could dramatically modulate the bandgap,crystallinity and surface electron structure of the LDH,leading to the remarkable improvement in its conductivity,exposed active sites and intrinsic electrochemical activity,and thus the OH^(*)and O^(*)adsorption free energy could be remarkably optimized,even at low temperatures.In addition,the low crystallinity C/N-CNMA is of great electrochemical compatibility with both the KOH aqueous electrolyte and the isobutyl alcohol(IPA)modulated organohydrogel electrolyte.By means of adjusting the solvation and hydrogen bonding in the electrolytes,the assembled hybrid supercapacitors deliver excellent energy density,power density and cycling stability in the temperature range of-30 to 25℃.Specifically,the gel electrolyte with IPA as the anti-freezing functional additive displays high flexibility and ionic conductivity at low temperatures.

Calibrating SECCM measurements by means of a nanoelectrode ruler.The intrinsic oxygen reduction activity of PtNi catalyst nanoparticles

Scanning electrochemical cell microscopy(SECCM)is increasingly applied to determine the intrinsic catalytic activity of single electrocatalyst particle.This is especially feasible if the catalyst nanoparticles are large enough that they can be found and counted in post-SECCM scanning electron microscopy images.Evidently,this becomes impossible for very small nanoparticles and hence,a catalytic current measured in one landing zone of the SECCM droplet cannot be correlated to the exact number of catalyst particles.We show,that by introducing a ruler method employing a carbon nanoelectrode decorated with a countable number of the same catalyst particles from which the catalytic activity can be determined,the activity determined using SECCM from many spots can be converted in the intrinsic catalytic activity of a certain number of catalyst nanoparticles.

Concordance among indices of intrinsic brain function： Insights from inter-individual variation and temporal dynamics

Various resting-state fMRI(R-fMRI) measures have been developed to characterize intrinsic brain activity. While each of these measures has gained a growing presence in the literature, questions remain regarding the common and unique aspects these indices capture. The present work provided a comprehensive examination of inter-individual variation and intra-individual temporal variation for commonly used measures, including fractional amplitude of low frequency fluctuations, regional homogeneity,voxel-mirrored homotopic connectivity, network centrality and global signal correlation. Regardless of whether examining intra-individual or inter-individual variation, we found that these definitionally distinct R-fMRI indices tend to exhibit a relatively high degree of covariation, which doesn't exist in phase randomized surrogate data. As a measure of intrinsic brain function, concordance for R-fMRI indices was negatively correlated with age across individuals(i.e., concordance among functional indices decreased with age). To understand the functional significance of concordance, we noted that higher concordance was generally associated with higher strengths of R-fMRI indices, regardless of whether looking through the lens of inter-individual(i.e., high vs. low concordance participants) or intra-individual(i.e., high vs.low concordance states identified via temporal dynamic analyses) differences. We also noted a linear increase in functional concordance together with the R-fMRI indices through the scan, which may suggest a decrease in arousal. The current study demonstrated an enriched picture regarding the relationship among the R-fMRI indices, as well as provided new insights in examining dynamic states within and between individuals.

半金属氢氧化物材料用于电化学水氧化

寻找具有高本征活性的水氧化催化剂材料对许多清洁能源技术的发展至关重要.氢氧化物半导体对析氧反应具有一定的电催化活性.然而,该材料导电性较差,限制着其电催化本征活性的提升.本文提出一种兼具高导电性和高催化活性的半金属氢氧化物析氧电催化材料.通过阳离子掺杂和阴离子空位协同作用,镍铁水滑石半导体可转化为半金属材料,其电阻率降低了两个数量级.相应半金属氢氧化物阵列电极的电催化活性显著提升,在10 mA cm^(-2)电流密度下其析氧过电势仅为195 mV,Tafel斜率仅为40.9 mV dec^(-1),显著优于商用RuO_(2)催化剂(316 mV,99.6 mV dec^(-1)).原位拉曼光谱和理论计算结果表明,半金属氢氧化物可在较低过电位下转化为羟基氧化物中间体,有助于高价态金属活性位点的形成与稳定,从而提升材料的析氧本征活性.本研究表明,兼具优异导电性和催化活性的半金属氢氧化物可作为先进的电极材料.

Multiscale engineering of molecular electrocatalysts for the rapid hydrogen evolution reaction

Molecular electrocatalysts have demonstrated potential for the hydrogen evolution reaction(HER)due to their well-defined structures and high intrinsic activities.Achieving rapid production of hydrogen requires molecular electrocatalysts to operate at high current densities,which still presents a challenge.In this work,we demonstrate that molecularly dispersed electrocatalysts of cobalt phthalocyanine anchored on carbon nanotubes(CoPc MDEs)are superior candidates due to the efficient charge transport between the substrate and the active site.The intrinsic activity can be enhanced by introducing functional groups on phthalocyanine.To facilitate mass transport,di(ethylene glycol)substituted CoPc molecules are further anchored on a threedimensional self-supported electrode(CoPc-DEG MDE@CC),enabling continuous operation for 25 h at−1000 mA/cm^(2)in 1.0 M KOH.Our study demonstrates the potential of molecular electrocatalysts for HER and emphasizes the importance of adjusting intrinsic activity,and charge and mass transport capacity for practical molecular electrocatalysts.

Electronic structure regulation of noble metal-free materials toward alkaline oxygen electrocatalysis

Developing highly efficient,inexpensive catalysts for oxygen electrocatalysis in alkaline electrolytes(i.e.,the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER))is essential for constructing advanced energy conversion techniques(such as electrolyzers,fuel cells,and metal–air batteries).Recent achievements in efficient noble metal-free ORR and OER catalysts make the replacement of conventional noble metal counterparts a realistic possibility.In particular,various electronic structure regulation strategies have been employed to endow these oxygen catalysts with attractive physicochemical properties and strong synergistic effects,providing significant fundamental understanding to advance in this direction.This review article summarizes recently developed electronic structure regulation strategies for three types of noble metal-free oxygen catalysts:transition metal compounds,single-atom catalysts,and metal-free catalysts.We begin by briefly presenting the basic ORR and OER reaction mechanisms,following this with an analysis of the fundamental relationship between electronic structure and intrinsic electrocatalytic activity for the three categories of catalysts.Subsequently,recent advances in electronic structure regulation strategies for noble metal-free ORR and OER catalysts are systematically dis-cussed.We conclude by summarizing the remaining challenges and presenting our outlook on the future for designing and synthesizing noble metal-free oxygen electrocatalysts.

Accelerated antibacterial red-carbon dots with photodynamic therapy against multidrug-resistant Acinetobacter baumannii

The emergence of antibiotic resistance in bacteria is a major public-health issue.Synthesis of efficient antibiotic-free material is very important for fighting bacterial infection-related diseases.Herein,red-carbon dots(R-CDs)with a broad range of spectral absorption(350–700 nm)from organic bactericides or intermediates were synthesized through a solvothermal route.The prepared R-CDs not only had intrinsic antibacterial activities,but also could kill multidrug-resistant bacteria(multidrug-resistant Acinetobacter baumannii(MRAB)and multidrug-resistant Staphylococcus aureus(MRSA))effectively by generating reactive oxygen species.Furthermore,R-CDs could eliminate and inhibit the formation of MRAB biofilms,while conferring few side effects on normal cells.A unique property of R-CDs was demonstrated upon in vivo treatment of antibiotic-sensitive MRABinduced infected wounds.These data suggested that this novel R-CDs-based strategy might enable the design of nextgeneration agents to fight drug-resistant bacteria.