Chalcogen heteroatoms doped nickel-nitrogen-carbon single-atom catalysts with asymmetric coordination for efficient electrochemical CO_(2) reduction

The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2) reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N_(4)-C)configuration to obtain Ni-X-N_(3)-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N_(3)-C(X:S,Se,and Te)SACs,Ni-Se-N_(3)-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98% at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2) battery integrated with Ni-Se-N_(3)-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm^(-2) and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N_(4)-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N_(3)-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of ^(*)COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.

Highly selective electrosynthesis of imines via electroreduction coupling of nitroarenes with aryl aldehydes on Co_(9)S_(8)with positively charged sulfur vacancies

The electrocatalytic synthesis of imines through the reductive imination of nitroarenes with aldehydes is a facile,environmentally friendly,and valuable process.In this study,high selectivity electrosynthesis of imines was realized through the electrocatalytic C-N coupling reaction between nitroarenes and aryl aldehydes on Co_(9)S_(8)nanoflowers with rich sulfur vacancies(Co_(9)S_(8)-Vs).Comparative experiments revealed that positively charged sulfur vacancies play a pivotal role in boosting catalytic selectivity towards imines.Electron-deficient sulfur vacancies intensified the adsorption of negatively charged Ph-NO_(2),thereby enhancing the conversion rate of the electrochemical nitrobenzene-reduction reaction(eNB-RR).Simultaneously,sulfur vacancies augmented the adsorption capability of negatively charged Ph-CHO,enriching Ph-CHO species at the electrode interface and expediting the Schiff base condensation reaction rate.The experimental results show that the reaction conditions can satisfy the different nitroarenes and aryl aldehydes in the electrocatalytic aqueous-phase system under mild conditions to obtain the corresponding imine products in high selectivity.This study provides a facile and environmentally friendly pathway for future electrocatalytic synthesis of imine.

电容器能量的3种求法

分别利用电容器的能量公式、电场的能量公式以及电荷系的静电能公式求出一般电容器所储存的能量．

First-principles Study on Enhanced Optical Stability of BaMgAl10O17：Eu^2＋ Phosphor by SiN Doping

Using density functional theory, we studied band structure, density of states, optical proper- ties and Mulliken population of the pure and SiN doped BaMgAl10017：Eu^2＋ （BAM：Eu^2＋） phosphors. Calculation results showed that the bands of BAM：Eu2＋ were of low band energy dispersion, indicating large joint density of states, hence high performance of optical absorption and luminescence. BAM：Eu^2＋ showed stronger absorption intensity while Eu^2＋ occupied the BR sites instead of the mO sites. The concentration of Eu^2＋ at BR sites increased while that at mO sites decreased after Si-N doping. The influence of the variation of Eu^2＋ distribution on the spectra was stronger than the influence of the decrease of Eu^2＋ PDOS when SiN concentration was lower than 0.25, therefore the absorption and luminescence intensity of BAM：Eu^2＋ were enhanced. Mulliken population of Si-N bond was higher than A1-O bond, while that of Eu-N bond was higher than Eu-O bond as well, indicating that Si-N bonds and Eu-N bonds possessed higher covalence than Al-O bonds and Eu-N bonds respectively. The existence of Si-N bonds and Eu-N bonds enhanced the local covalence of Eu^2＋, hence the optical stability of BAM：Eu^2＋.

NaNO_2晶体线性和非线性光学系数的计算

使用从头计算平面波赝势方法 ,计算了NaNO2 晶体电子能带结构 ,并使用改进的倍频公式计算了它的线性折射率和静态二级非线性系数 ,所得到的结果和实验值相符 .采用实空间原子切割方法分析了阳离子和阴离子基团对光学性质的贡献 .计算表明 (NO2 ) - 基团对双折射率和倍频系数的贡献占主要地位 。