A DFT Study of Surface and Catalysis Processes at Pt-based Nanoparticles

本论文的主要工作是从理论基础角度上来研究一些重要工业反应，例如蒸汽甲烷重整和水煤气变换反应与铂催化剂结构灵敏性的关系。使用第一性原理的密度泛函理论方法分析铂和钯的表面结构和表面基元反应，并通过与热力学反应条件相关联研究铂的表面性质，同时通过微观动力学反应模型来模拟计算体系的宏观反应情况。研究工作旨在阐明在不同反应体系下的高指数铂纳米晶面的反应能垒和与之相关的反应途径，并通过与低指数密堆积表面，和不同金属如铑和钯等贵金属的不同表面相比较进一步深入认识铂高指数晶面对反应活性的影响。在一般情况下，具有开放表面的纳米粒子比表面原子紧密排列的纳米粒子显示出更优异的催化活性，这主要是因为开放表面具有更高密...The aim of the present work is to understand the structure sensitivity of catalysis by Pt from a fundamental point of view for a number of industrially important reactions i.e. steam methane reforming andthe water-gas shift reaction. To accomplish this,we used quantum-chemical studies to analyze the structure of Pt and Pd surfaces as a function of the thermodynamic conditions, the elementary react...学位：理学博士院系专业：化学化工学院_物理化学(含化学物理)学号：2052008015020

苦菜不同部位提取物的抗氧化活性

分别用水、乙醇(体积分数分别为25%、50%、75%)和无水乙醇,对苦菜的根、茎、叶、花4个部位进行冷浸提取。测定不同处理条件下的提取率,并用DPPH自由基清除法检测提取物的抗氧化活性;测定提取物的总黄酮和总多酚类物质的含量及其EC50。结果表明:用50%乙醇提取的苦菜各部位提取率最高,不同部位不同溶剂提取物的抗氧化活性均呈明显的剂量关系;提取物的抗氧化活性与其中总黄酮和总多酚的含量有关;不同部位的抗氧化能力大小为:花>叶>茎>根

Study of kinetics of dissociative adsorption of formic acid on electrode of tetrahexahedral platinum nanocrystals

研究了甲酸在二十四面体PT纳米晶(THHPTnCS)电极表面解离吸附反应过程.电化学原位红外反射光谱结果显示,甲酸在低电位(-0.20V(SCE))即可在THHPTnCS电极上氧化到CO2,同时发生分子内化学键断裂生成吸附态CO物种.运用程序电位阶跃暂态方法定量研究甲酸解离吸附反应动力学,测得5x10-3MOl·l-1 HCOOH+0.1MOl·l-1 H2SO4溶液中甲酸在THHPTnCS电极上解离吸附的最大平均速率υAMAX为13.19x10-10MOl·CM-2·S-1,是商品PT/C催化剂电极上υAMAX的1.5倍.研究结果揭示了THHPTnCS的反应活性显著高于PT/C催化剂.The present paper studies the kinetics of dissociative adsorption of formic acid on electrode of tetrahexa-hedral platinum nanocrystals (THH Pt NCs).In situ FTIR spectroscopic results demonstrated that HCOOH can beoxidized to CO2 at a low potential (-0.20 V(SCE)) on the THH Pt NCs electrode, and the chemical bonds inside for-mic acid molecule are broken to form adsorbed COL species.The kinetics of the dissociative adsorption of HCOOHwas quantitatively investigated by employing programmed potential step technique.It has been determined that, in5×10?3 mol·L-1 HCOOH + 0.1mol·L-1 H2SO4 solution, the maximal value of the average rate (υa max) of dissociativeadsorption of HCOOH on a commercial Pt/C catalyst electrode is 8.58×10-10 mol·cm-2·s-1, while on the THH Pt NCsthe υamax is 1.5 times larger than the υamax measured on Pt/C and reaches 13.19×10-10 mol·cm-2·s-1.The results haverevealed that the reactivity of the THH Pt NCs is much higher than that of the Pt/C catalysts.国家自然科学基金(批准号:20833005;20873113)资

in situ FTIR Spectroscopic Studies of Adsorption and Oxidation of L-Serine on Pt Electrodes in Neutral Solutions

运用电化学循环伏安(CV)和原位红外反射光谱(In SITufTIrS)研究了中性介质中l-丝氨酸在PT电极上的解离吸附和氧化过程.结果表明,在中性溶液中,以两性离子形式存在的丝氨酸可以在很低的电位下(-0.6 V,VS.SCE)在PT电极表面发生解离吸附,生成强吸物种一氧化碳(COl)、(COb)和氰负离子(Cn-).研究结果还表明,当电位低于0.7 V(VS.SCE)时,Cn-能稳定存在于电极表面,抑制丝氨酸的进一步反应.在更高电位时则主要为丝氨酸分子的氧化过程.The dissociative adsorption and oxidation of L-serine on platinum electrode in neutral solutions were studied via in situ FTIR reflection spectroscopy and electrochemical methods.The FTIRS results demonstrate that the serine can be easily dissociated on Pt surface at potentials below-0.6 V(vs.SCE) to form cyanide(--2100 cm-1) and carbon monoxide(COL,--2034 cm-1;COB,--1870 cm-1).The observation of an absorption band at 2343 cm-1 is ascribed to CO2,which implies the cleavage of the C—C bond during the dissociative adsorption of serine.It has determined that the cyanide was strongly adsorbed on electrode surface in a wide potential region below 0.7 V(vs.SCE) and inhibited the oxidation of serine.At higher potentials,the serine molecules could be oxidized directly to yield the main product CO2 species.As the pH decreased in the spectroelectrochemical cell during serine reactions,the acidic serine species also detected.The present study revealed the interaction of serine with Pt electrode surface,and suggested a possible reaction mechanism of serine on Pt electrode surface in neutral solutions.国家自然科学基金(批准号:20673091;20833005)资

Depression recognition based on speech analysis

抑郁症是世界范围内常见的精神疾病之一,抑郁症患者往往长期伴随情绪低落,如悲伤内疚、低自尊、兴趣丧失、功能减退等,对个人、家庭及社会造成了巨大损失.抑郁症的发病原因复杂,临床诊断存在一定的困难,有必要寻找一种更加便捷、客观、高效的方式来辅助抑郁症的快速识别.语音作为一个相对客观且容易获得的变量,具有其潜在的价值.本研究旨在构建基于语音的抑郁症识别模型,探究语音与抑郁症之间的关系.收集了103名被试(45名抑郁症患者,58名健康人)的语音数据,实验组为临床确诊的抑郁症患者,年龄在23.8~44.6岁之间,控制组为健康人,年龄为20.1~41.7岁.我们采用了3(情绪状态:正性、中性、负性)&times;3(任务类型:语言问答、文本朗读、图片描述)的实验设计,运用机器学习的分类算法&mdash;&mdash;逻辑回归(LR)来构建抑郁识别模型.实验结果表明,语音的抑郁识别精度可以达到82.9%.本文采用机器学习方法,基于语音变量建立有效的抑郁症自动识别模型,为抑郁症的辅助识别提供客观的指标和依据.</p

in situ FTIR Spectroscopic Studies of Adsorption and Oxidation of L-Serine on Pt Electrodes in Neutral Solutions

The dissociative adsorption and oxidation of L-serine on platinum electrode in neutral solutions were studied via in situ FTIR reflection spectroscopy and electrochemical methods. The FTIRS results demonstrate that the serine can be easily dissociated on Pt surface at potentials below -0.6 V (vs. SCE) to form cyanide (similar to 2100 cm(-1)) and carbon monoxide(COL, similar to 2034 cm(-1); COB, similar to 1870 cm(-1)). The observation of an absorption band at 2343 cm(-1) is ascribed to CO2, which implies the cleavage of the C-C bond during the dissociative adsorption of serine. It has determined that the cyanide was strongly adsorbed on electrode surface in a wide potential region below 0.7 V(vs. SCE) and inhibited the oxidation of serine. At higher potentials, the serine molecules could be oxidized directly to yield the main product CO, species. As the pH decreased in the spectroelectrochemical cell during serine reactions, the acidic serine species also detected. The present study revealed the interaction of serine with Pt electrode surface, and suggested a possible reaction mechanism of serine on Pt electrode surface in neutral solutions