Regulating local charges of atomically dispersed Moδ+ sites by nitrogen coordination on cobalt nanosheets to trigger water dissociation for boosted hydrogen evolution in alkaline media

Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an excellent HER catalyst due to its suitable H*binding,its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics.In this work,nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Mo^(δ+)sites on Co nanosheets to trigger water dissociation.Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Mo^(δ+)sites.To realize this speculation,atomically dispersed Mo^(δ+)sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO_(4).High angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and X-ray absorption spectroscopy(XAS)demonstrate the coordination of N atoms with atomically dispersed Mo atoms,leading to the local charges of atomically dispersed Mo^(δ+)sites in Mo(N)/Co.The measurement from ambient pressure X-ray photoelectron spectroscopy(AP-XPS)reveals that the Mo^(δ+)sites promote the adsorption and activation of water molecule.Therefore,the Mo(N)/Co exhibits an excellent activity,which need only an overpotential of 39 mV to reach the current density of 10 mA cm^(-2).The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.

Pressure-Induced Charge-Order Melting and Reentrant Charge Carrier Localization in the Mixed-Valent Pb3Rh7O15

The mixed-valent Pb3Rh7O15 undergoes a Verwey-type transition at Tv≈180K, below which the development of Rh3＋3＋/Rh4＋4＋ charge order induces an abrupt conductor-to-insulator transition in resistivity. Here we investigate the effect of pressure on the Verwey-type transition of Pb3Rh7O15 by measuring its electrical resistivity under hydrostatic pressures up to 8GPa with a cubic anvil cell apparatus. We find that the application of high pressure can suppress the Verwey-type transition around 3GPa, above which a metallic state is realized at temperatures below ～70K, suggesting the melting of charge order by pressure. Interestingly, the low-temperature metallic region shrinks gradually upon further increasing pressure and disappears completely at P〉7GPa, which indicates that the charge carriers in Pb3Rh7O15 undergo a reentrant localization under higher pressures. We have constructed a temperature-pressure phase diagram for Pb3Rh7O15 and compared to that of Fe3O4, showing an archetype Verwey transition.

Charge Localization Induced by Reorientation of FA Cations Greatly Suppresses Nonradiative Electron-Hole Recombination in FAPbI3 Perovskites:a Time-Domain Ab Initio Study

Recent experiments report the rotation of FA(FA=HC[NH2]2+)cations significantly influence the excited-state lifetime of FAPbI3.However,the underlying mechanism remains unclear.Using ab initio nonadiabatic(NA)molecular dynamics combined with time-domain density functional simulations,we have demonstrated that reorientation of partial FA cations significantly inhibits nonradiative electron-hole recombination with respect to the pristine FAPbI3 due to the decreased NA coupling by localizing electron and hole in different positions and the suppressed atomic motions.Slow nuclear motions simultaneously increase the decoherence time,which is overcome by the reduced NA coupling,extending electron-hole recombination time scales to several nanoseconds and being about 3.9 times longer than that in pristine FAPbI3,which occurs within sub-nanosecond and agrees with experiment.Our study established the mechanism for the experimentally reported prolonged excited-state lifetime,providing a rational strategy for design of high performance of perovskite solar cells and optoelectronic devices.

A Hypothesis Regarding the Origin of Additional Surface Acidity in Solid Complexes with Same Metal Cations

Based on the criteria for additional surface acidity generation in composite oxides and composite fluorides proposed by Tanabe and Kemnitz et al.A hypothesis for the origin of additional surface acidity in solid composites with the same metal cations is proposed.The surface acidsites of We analyze three types of solid composite systems,that is,CrF_(3)/Cr_(2)O_(3),MgF_(2)/MgO,and ZnF_(2)/ZnO,is systematically analyzed,which agrees with experimental results.Accordingly,the origin of additional surface acidity in these solid composites is reasonably explained,and the types of acidic sites are also predicted.

调控三芴酮基共价有机框架中的局域极化促进光催化析氢活性

局部电荷的强离域和强偶极矩是影响共价有机框架(COFs)基光催化剂催化析氢性能的两个关键因素.然而,基于精确的调控结构模型来系统研究这种构效关系的报告相对较少.本研究提出了一种新的策略,通过合理的设计,制备了三种三芴酮基COFs,通过在分子水平上调控单体的结构和偶极来提高局部电荷离域指数.我们重点研究这三种三芴酮基COF的局部电荷离域与光催化性能之间的构效关系.在不同三芴酮基COF中,1,3,5-三(对甲酰基苯基)苯基COF(TeTpb-COF)展现出21.6 mmol g^(-1)h^(-1)的最高析氢速率,与2,4,6-三(4-醛基苯基)-1,3,5-三嗪基COF(TeTt-COF,0.2mmol g^(-1)h^(-1))相比,光催化析氢性能提高了108倍.这种性能的增强可归因于其强大的分子内置电场提高了供体-受体嵌段单元中光生电荷的有效分离效率.这项工作证实了调整构建块可以极大增强三芴酮基COFs中的局部偶极矩,从而显著改善光催化析氢性能.构建模块的调控策略为创建高效的新型COF基光催化析氢平台提供了新机会.

Efficient and Fast X-Ray Luminescence in Organic Phosphors Through High-Level Triplet-Singlet Reverse Intersystem Crossing

Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbidden transitions in these materials often result in long-lived phosphorescence,which is undesirable for ultrafast X-ray detection and imaging.Here we demonstrate that the effect of hybridized local and charge-transfer(HLCT)excited states enables organic scintillators to exhibit highly efficient and fast radioluminescence(RL)in response to X-ray irradiation.Our experimental and theoretical investigation shows that the oxidized 1,8-naphthalimide-phenothiazine dyad(OMNI-PTZ 2)with HLCT-excited states has an enhanced overlap integral of the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)on MNIπ-orbitals,and moderate donor–acceptor electron interactions.As a result,the RL of these crystals exhibits a 61-fold increase and its monoexponential decay lifetime is three orders of magnitude faster compared to its corresponding thermally activated delayed fluorescence(TADF)molecule MNI-PTZ 1.We further demonstrate the practical utility of the OMNI-PTZ 2(G)in high-performance X-ray detection and imaging,achieving an X-ray dose sensitivity of 97 nGy s−1 and an exceptional spatial resolution of 20 lp/mm.Our study provides a promising molecular design principle for utilizing triplet excitons to develop high-efficiency and fast X-ray scintillators for the development of next-generation flexible and stretchable X-ray imaging detectors.