Correlating the electronic structure of perovskite La_(1-x)SrxCoO_(3) with activity for the oxygen evolution reaction:The critical role of Co 3d hole state

Perovskite LaCoO_(3) is being increasingly explored as an effective low-cost electrocatalyst for the oxygen evolution reaction(OER).Sr doping in LaCoO_(3)(La1-xSrxCoO_(3))has been found to substantially increase its catalytic activity.In this work,we report a detailed study on the evolution of the electronic structure of La1-xSrxCoO_(3) with 0≤x≤1 and its correlation with electrocatalytic activity for the OER.A combination of X-ray photoemission spectroscopy(XPS)and X-ray absorption spectroscopy(XAS)was used to unravel the electronic density of states(DOS)near the Fermi level(EF),which provide insights into the key electronic structure features for the enhanced OER catalytic activity.Detailed analysis on the Co L-edge XAS suggest that LaCoO_(3) has a low spin state with t_(2g)^(6) e_(g)^(0) configuration at room temperature.This implies that the high OER catalytic activity of LaCoO_(3) should not be rationalized by the occupancy of eg=1 descriptor.Substituting Sr^(2+) for La^(3+) in LaCoO_(3) induces Co4+oxidation states and effectively dopes hole states into the top of valence band.A semiconductor-to-metal transition is observed for x>0.2,due to the holeinduced electronic DOS at the EF and increased hybridization between Co 3 d and O 2 p.Such an electronic modulation enhances the surface adsorption of the*OH intermediate and reduces the energy barrier for interfacial charge transfer,thus improving the OER catalytic activity in La_(1-x)Sr_(x)CoO_(3).In addition,we found that the La_(1-x)Sr_(x)CoO_(3) surface undergoes amorphization after certain period of OER measurement,leading to a partial deactivation of the electrocatalyst.High Sr doping levels accelerated the amorphization process.

Comparative Study of Corrosion Inhibition Efficiency of Naturally Occurring Ecofriendly Varieties of Holy Basil (Tulsi) for Tin in HNO₃Solution

Weight loss technique has been used to study the corrosion inhibition efficiency of tin in HNO3 solution by using the leaves and stem extract of different varieties of Holy Basil viz. ocimum basilicum (EB),, ocimum cannum (EC) and ocimum sanctum (ES). The results show that all the varieties under study are good corrosion inhibitors, among which leaves extract of EB is the most effective. Corrosion inhibition efficiency increases with increasing concentration of inhibitor and it also increases with increasing concentration of HNO3 solution. Inhibition efficiency was found maximum up to 96.19% for tin in with 0.6% leaves extract.

A Possible Structure of the Al36 Cluster： Coexistence of Icosahedral and fcc-Like Structures

We study the atomic and electronic structures of the Al36 cluster using first principles total energy calculations with the local density approximation, and obtain a structure which has a HOMO-LUMO gap as large as 0.67eV, in agreement with experimental photoelectron spectroscopy. Its atomic structure is found to show the coexistence of icosahedral and fcc-based structures, which can be seen as a transition phase from icosahedral to fcc-bulk structures.

Promoting effect of interfacial hole accumulation on photoelectrochemicalwater oxidation in BiVO_(4)and Mo-doped BiVO_(4)

Hole transfer at the semiconductor-electrolyte interface is a key elementary process in(photo)electrochemical(PEC)water oxidation.However,up to now,a detailed understanding of the hole transfer and the influence of surface hole density on PEC water oxidation kinetics is lacking.In this work,we propose a model for the first time in which the surface accumulated hole density in BiVO_(4)and Mo-doped BiVO_(4)samples during water oxidation can be acquired via employing illumination-dependent Mott-Schottky measurements.Based on this model,some results are demonstrated as below:(1)Although the surface hole density increases when increasing light intensity and applied potential,the hole transfer rate remains linearly proportional to surface hole density on a log-log scale.(2)Both water oxidation on BiVO_(4)and Mo-doped BiVO_(4)follow first-order reaction kinetics at low surface hole densities,which is in good agreement with literature.(3)We find that water oxidation active sites in both BiVO_(4)and Mo-doped BiVO_(4)are very likely to be Bi^(5+),which are produced by photoexcited or/and electroinduced surface holes,rather than VO_(x)species or Mo^(6+)due to their insufficient redox potential for water oxidation.(4)Introduction of Mo doping brings about higher OER activity of BiVO_(4),as it suppresses the recombination rate of surface holes and increases formation of Bi^(5+).This surface hole model offers a general approach for the quantification of surface hole density in the field of semiconductor photoelectrocatalysis.

Rare earth oxides doped NiO/γ-Al_2O_3 catalyst for oxidative dehydrogenation of cyclohexane

The effect of rare earth oxides （RE=Ce, La, Gd, and Dy） doping of alumina support in NiO/7-A1203 system was investi- gated on its catalytic performance in oxidative dehydrogenation （ODH） of cyclohexane. The physicochemical properties of various samples were followed up through N2 physisorption, temperature programmed reduction （H2-TPR）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and potentiometric acid-base titration techniques. In the parent NiO/y-A1203 catalyst, Ni species were found to be strongly interacted with alumina surface. Addition of rare earth dopants to ）＇-A1203 in the catalyst system affected the nickel-alumina interaction and resulted in significant modifications in the catalytic performances in the ODH reaction. The results re- vealed the beneficial role of both La203 and Gd2Os doping in enhancing the ODH catalytic activity and selectivity to cyclohexene. H2-TPR and XPS results indicated that majority of Ni species in NiO/La203 modified T-A1203 were more weakly interacted with La203 and alumina whereas both NiO like species and nickel aluminate were present on the surface. Doping with cerium or dyspro- sium increased the nickel-support interaction and led to a decrease in surface nickel concentration. In case of doping with Ce, surface concentration of cerium oxide was higher than those of the other RE oxides; the doped catalyst reached its steady state activity faster than the other catalysts. The acid-base results suggested that RE metals were interacted most likely with acidic surface hydroxyl groups. The degree of nickel-alumina interaction decreased in the following order： LaAI〉GdAI〉CeAI〉DyA1.

Flame-retardant properties of in situ sol-gel synthesized inorganic borosilicate/silicate polymer scaffold matrix comprising ionic liquid

This paper focuses on the superiority of organic?inorganic hybrid ion-gel electrolytes for lithiumion batteries(LiBs)over commercial electrolytes,such as 1 M LiPF6 in 1:1 ethylene carbonate(EC):dimethyl carbonate{DMC){1 M LiPF6-EC:DMC},in terms of their flame susceptibility.These ion-gel electrolytes possess ionic liquid monomers,which are confined within the borosilicate or silicate matrices that are ideal for nonflammability.Naked flame tests confirm that the organicinorganic hybrid electrolytes are less susceptible to flames,and these electrolytes do not suffer from a major loss in terms of weight.In addition,the hybrids are self-extinguishable.Therefore,these hybrids are only oxidized when subjected to a flame unlike other commercial electrolytes used in lithium-ion batteries.Supplementary analyses using differential scanning calorimetric studies reveal that the hybrids are glassy until the temperature reaches more than 100℃.The current results are consistent with previously published data on the organic-inorganic hybrids.

Structure and photochromism of spiropyran assemblies

Nanocluster assemblies of spiropyran compounds have been prepared by means of LB technique, and the relations between the subphase, pH value, condition of preparation and the structure of the fabricated LB film are systematically investigated. The stability, photochromic fatigue properties of the spiropyran LB film, which are of primary importance in optic signal storage applications, are also studied in detail. A kind of supermolecular film with homogeneously distributed J aggregates of similar granular size has been obtained with the optical resolution in the order of micrometer. Finally, a nondestructive readout method for such an LB film to be used as the optic signal storage film is proposed.

CuSbS_(2)薄膜光阴极的电子结构及其在光电催化分解水制氢的应用

硫化锑铜(CuSbS_(2))是一种p型半导体,带隙为1.5 eV,同时拥有较大的光吸收系数(>105cm-1),因此在光电催化领域拥有广阔的应用前景.但是目前国内外的研究还缺乏对CuSbS_(2)电子结构以及其如何影响PEC性能的深入理解.为了进一步改善CuSbS_(2)的PEC性能,对其电子结构进行一系列表征分析是非常重要的.本文中,我们利用同步辐射技术揭示了CuSbS_(2)的电子结构.结果表明,CuSbS_(2)的价带(VB)由S 3p和Cu 3d的强杂交态组成,同时Sb 5p/5s也有部分影响.基于以上理论指导,我们设计了一种高质量Cu Sb S_(2)薄膜的制备技术,并使用FTO/CuSbS_(2)/CdS/Pt光电阴极在0.0 V下实现了CuSbS_(2)基材料的高光电流密度(6.3 mA cm^(-2)).

Inductive effect of Ti-doping in Fe_(2)O_(3)enhances the photoelectrochemical water oxidation

Hematite(α-Fe_(2)O_(3))is an ideal oxide semiconductor candidate for photoelectrochemical(PEC)water splitting.Doping of Fe_(2)O_(3)is known to benefit the PEC water oxidation efficiency,but despite extensive research efforts,the underlying mechanism still remains elusive.In this work,we report a comprehensive study on the relationship between the electronic structure,interfacial reaction kinetics and PEC activity of Ti-doped Fe_(2)O_(3)photoanodes.The results show that the interfacial charge transfer efficiency at the Fe_(2)O_(3)/electrolyte interface is the main factor in the significant increase of the PEC activity of doped Fe_(2)O_(3).Electrochemical impedance spectroscopy reveals that the interfacial charge transfer efficiency is determined by energy overlap between the water oxidation potential and energy distribution of an intermediate surface state that has been identified as Fe^(IV)=O groups on Fe_(2)O_(3)surface generated during PEC process.Interestingly,the potential energy distribution of this intermediate surface state can be modulated by Ti doping,and a shift towards a more positive potential of the intermediate surface state increases the overlap with the water oxidation potential and thus enhances the kinetics of charge transfer for PEC water splitting.The origin of such potential energy modulation is traced to the inductive effect from Ti-doping on the Fe^(3+)/Fe^(4+)redox transition and the Fe-O bond covalency.Our results provide new insight into the mechanism for the doping effect on the PEC water splitting,introducing new strategies to optimize the PEC activity by tuning the redox properties of active metal oxides.