Electrochemical in situ fast time-resolved microscope FTIR reflection spectroscopy and its applications in the studies of surface dynamic processes on nanostructured Pt electrodes

固液界面电化学原位红外反射光谱利用指纹特征和表面选律，检测电极表面吸附物种及其成键和取向，在分子水平上研究反应机理。时间分辨和空间分辨是原位红外光谱两个重要的发展方向。其中时间分辨光谱，在检测短寿命中间体，跟踪反应历程，获取分子水平层次的动力学规律等方面可提供独到的信息。本论文自行设计并研制信号同步仪，采用微电极并与红外显微镜相结合，建立了外反射型电化学原位步进扫描时间分辨显微FTIR光谱(insituSSTR-MFTIRS)，光谱的时间分辨率最快可达10ms。利用纳米结构电极的异常红外效应,显著提高光谱检测灵敏度，克服了通常薄层电解池中电极对电位变化响应慢的不足，拓宽了快速时间分辨红外光谱的...Electrochemical in situ infrared reflection spectroscopy, on the basis of its fingerprint and surface selection rules, can identify the nature of adsorbates and their surface bonding and orientation in electrode/electrolyte interfaces. The time-resolved and space-resolved spectroscopy have become currently two main directions of the development of electrochemical in situ IR spectroscopy. The forme...学位：理学博士院系专业：化学化工学院化学系_物理化学(含化学物理)学号：B20002503

关于会计理论研究方法体系的探讨

关于会计理论研究方法体系的探讨厦门大学周润书，项有志一、建立会计理论研究方法体系的意义1.会计理论研究方法贯穿于会计理论研究的始终，其本身就是会计理论体系的重要组成部分，其研究成果可以直接丰富和发展会计理论体系。科学的研究方法是产生科学理论的先导，是..

Experimental Boosting of the Oxygen Reduction Activity of an Fe/N/C Catalyst by Sulfur Doping and Density Functional Theory Calculations

向Fe/N/C非贵金属催化剂中再引入S掺杂是进一步提高其氧还原催化活性的有效方法。为了探究活性提高的原因,本文以三聚氰胺-甲醛树脂为前驱体,氯化; 钙为模板,氯化铁为铁源,通过添加硫氰化钾(KSCN)来控制热解催化剂的S掺杂量。通过对比分析催化剂的物化性质,结合密度泛函理论(DFT)计算,分; 析S掺杂促进Fe/N/C催化剂氧还原活性的原因。透射电子显微镜(TEM)和N_2吸脱附等温线测试结果表明,S元素可抑制含铁纳米粒子的形成,促使形; 成多孔碳结构,提高比表面积。X射线光电子能谱(XPS)结果表明,适量S前驱体可实现较高的S掺杂含量,得到最优的活性,过量的S反而会导致Fe和S的; 掺杂量同时降低,影响活性。DFT计算结果表明在Fe-N_4大环中引入S掺杂,可增强O_2分子和中间体OOH与Fe-N_4结构中的Fe的相互作用,; 促进形成Fe―O键,从而导致O―O键的键能显著降低,为后续反应O―O键的断裂提供可能,促进ORR反应的进行。S doping in Fe/N/C non-precious metal catalysts is an effective approach to further improve their catalytic activity for the oxygen reduction reaction (ORR). However, the enhancement mechanism is not yet clear. Here, we synthesized an Fe/N/C catalyst using melamine-formaldehyde resin as the N and C precursors, CaCl2 as the template, and FeCl3 as the Fe precursor. The effects of S doping on the morphology, textural property, composition, and ORR catalytic activity were investigated by adding various amounts of KSCN as a precursor. Transmission electron microscopy (TEM) and N-2 adsorption-desorption isotherm results revealed that S prevented the growth of Fe-containing nanoparticles, and facilitated the formation of a porous structure, which increased both the catalyst surface area and mass transfer rate. X-ray photoelectron spectroscopy (XPS) results indicated that a suitable amount of S precursor led to a high doping level of S and provided the highest ORR activity. However, too much S in the precursor decreased the doping levels of both Fe and S, due to the formation of FeS, which could be completely removed by acid leaching. Density functional theory (DFT) calculations showed that the addition of S in an Fe-N-4 macrocycle could enhance the interaction strength of the Fe-O bond between the O-2 molecule or the intermediate OOHspecies and Fe in the Fe-N-4 structure, resulting in a significant decrease in the O-O bond energy, and may help in bond breaking in subsequent reactions, facilitating the ORR process.National Natural Science Foundation of China [21373175, 21621091

Surface processes and kinetics of CO2 reduction on Pt(100) electrodes of different surface structure in sulfuric acid solutions

The reduction of CO2 on a Pt(100) electrode in CO2 saturated 0.5 M H2SO4 solutions was studied by in situ FTIR reflection spectroscopy and a programmed potential step technique. Different surface structures of Pt(100) electrode were prepared by different treatments including fast potential cycling (200 V s(-1)) for a known time. The Pt(100) surface was characterized by a parameter gamma that designates the relative amplitude of the current peak of hydrogen adsorption on (100) sites distributed on the one-dimensional surface domains to that on the two-dimensional surface domains. The in situ FTIR spectroscopic results demonstrated that the reduction of CO2 on the Pt(100) dominated by two-dimensional surface domains produced only bridge-bonded CO (COB) species, which give rise to IR absorption near 1840 cm(-1). However both bridge- and linear-bonded CO (COL, yielding IR absorption at around 2010 cm(-1)) species are found for CO2 reduction on the Pt(100) dominated by one-dimensional surface domains. The small intensity of the COL and COB bands indicates that coverage by reduced CO2 species (r-CO2. or COL and COB species) is low. The cyclic voltammetric (CV) studies confirmed quantitatively the in situ FTIRS results, and revealed that the r-CO2 species adsorb preferentially on (100) sites distributed on the two-dimensional surface domains. The initial rate of CO2 reduction upsilon (i), i.e., the rate of CO2 reduction on a clean Pt(100) surface, has been determined quantitatively from studies using a programmed potential step technique. It has been demonstrated that the maximum values of upsilon (i)(upsilon (m)(i)) measured on Pt(100) electrodes with different surface structures all appeared at -0.19 V. From analysis of the relationship between upsilon (m)(i) and gamma we have determined that the upsilon (m)(i) of CO2 reduction on (100) sites distributed on the two-dimensional surface domains is 0.53 x 10(-11) mol cm(-2) s(-1) and that on (100) sites distributed on the one-dimensional surface domains is approximately 2.66 x 10(-11) Mol cm(-2) s(-1). Based on in situ FTIRS and electrochemical studies a migration process of the r-CO2 from the one-dimensional surface domains to the two-dimensional surface domains has been proposed to be involved in CO2 reduction. The present study has thrown new light on the electrocatalytic activity of different surface structures of a Pt(100) electrode and the surface processes and kinetics of CO2 reduction

碳基非贵金属氧还原电催化剂的活性位结构研究进展

以热解型Fe/N/C为代表的碳基非贵金属材料被认为是当前最具潜力替代铂的非贵金属氧还原催化剂,其综合性能的进一步突破,对于推动质子交换膜燃料电池商业化应用具有重要意义。对热解型Fe/N/C...国家自然科学基金(21703184,91645121);; 国家重点研发计划(2017YFA0206500)资助项目~

Electrochemical Behavior of Irreversibly Adsorbed Sb on Au Electrode

用电化学循环伏安法和电化学石英晶体微天平(EQCM)技术研究了Sb在Au电极上不可逆吸附的电化学过程.研究结果表明,在-0.25V到0.18V(vs SCE)范围内,Sb可在Au电极上稳定吸附,并且在0.15V附近出现特征氧化还原峰.根据EQCM实验数据,在电位0.18V时,Sb在Au电极上的氧化产物是Sb2O3;同时Sb的吸附阻止了电解液中阴离子和水在Au电极上的吸附.当电极电位超过0.20V时,Sb2O3会被进一步氧化成Sb5+化合物,同时逐渐从Au电极表面脱附.The electrochemical processes of irreversibly adsorbed antimony (Sbad) on Au electrode were investigated by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). CV data showed that Sbad on Au electrode yielded oxidation and reduction features at about 0.15 V (vs saturated calomel electrode, SCE). EQCM data indicated that Sbad species were stable on Au electrode in the potential region from-0.25 to 0.18 V (vs SCE);the adsorption of Sb inhibited the adsorption of water and anion on Au electrode at low electrode potentials. Sb2O3 species was suggested to form on the Au electrode at 0.18 V. At a potential higher than 0.20 V the Sb2O3 species could be further oxidized to Sb(V) oxidation state and then desorbed from Au electrode.国家自然科学基金(20673091,20433060

Electrochemical and In Situ FTIR Studies of Adsorption and Oxidation of Dimethyl Ether on Platinum Electrode

运用电化学循环伏安法(CV)和原位傅立叶变换红外(FTIR)反射光谱,研究了不同pH值溶液中二甲醚(DME)在Pt电极上的解离吸附和氧化过程.稳态CV结果给出,在0.1mol·L-1H2SO4溶液中,当电位处于0.05-0.35V(vsRHE)区间,约70%的Pt表面位被DME的解离吸附产物占据.DME电氧化反应的活性随pH值增加而下降,在0.1mol·L-1NaOH溶液中,氢的吸脱附几乎不受抑制且观察不到明显的氧化电流,表明DME醚键上氧原子的质子化是其发生解离吸附和氧化的必要条件.原位FTIR光谱研究给出DME解离吸附和氧化过程的分子水平信息,指出DME在低电位区间解离生成线型吸附态CO(COL)毒性中间体.当电位高于0.55V(vsRHE)时,COL开始氧化为CO2;在0.75-1.00V(vsRHE)的电位区间则可同时发生经活性中间体(HCOOH)的氧化过程.Dissociative adsorption and electrooxidation of dimethyl ether (DME) on a platinum electrode in different pH solutions were studied using cyclic voltammetry (CV) and in situ FTIR reflection spectroscopy. The coverage of the dissociative adsorbed species was measured about 70% from hydrogen adsorption-desorption region (0.05-0.35 V(vs RHE)) of steady-state voltammogram recorded in 0.1 mol·L-1 H2SO4 solution. It was found that the electrochemical reactivity of DME was pH dependent, i.e., the larger the pH value was, the less the reactivity of DME would be. No perceptible reactivity of DME in 0.1 mol·L-1 NaOH solution could be detected. It was revealed that the protonation of the oxygen atom in the C-O-C bond played a key role in the electrooxidation of DME. In situ FTIR spectroscopic results illustrated that linearly bonded CO (COL) species determined at low potential region were derived from the dissociative adsorption of DME and behaved as 'poisoning' intermediate. The COL species could be oxidized to CO2 at potential higher than 0.55 V (vs RHE), and in the potential range from 0.75 to 1.00 V (vs RHE) DME was oxidized simultaneously via HCOOH species that were identified as the reactive intermediates.国家自然科学基金(20433060,20673091)资助项

In Situ FTIR Spectrocopic Studies of CO and CN~- Adsorbed on Electrode of Nanometer Thin Film of Palladium in Alkaline Solutions

以原位FTIR反射光谱研究碱性介质中CO和CN-在纳米Pd膜电极上的吸附和共吸附 ,进一步揭示了纳米薄膜材料的异常红外效应和CO与CN-共吸附时的相互作用规律。The adsorption and coadsorption of CO and CN- - on electrode of nanometer thin film of palladium (nm-Pd/GC)was studied by usin g in situ FTIR spectroscopy.The results demonstrated that the nm-Pd/GC electrod e exhibited abnormal infrared effects (AIREs) in alkaline solutions as in acid s olutions.The characters of AIREs,i.e.,the inversion of the direc tion of IR band,the augmentation of FWHM and the significant enhancement of IR a bsorption by adsorbed species were observed in all cases of adsorption and coads orption of CO and CN--.It has been illustrated that strong interaction is exis ted between adsorbed CO and CN-- on nm-Pd/GC surface.The study has contribute d towards understanding the surface processes of chemisorption as well as to rev eal the origin of nanometer size-effects of thin film materials.国家自然基金!(2 98330 60 );; 教育部博士点基金!(1 9990 3840 3)资

Enhancement of the electrocatalytic activity of Pt nanoparticles in oxygen reduction by chlorophenyl functionalization

NSF [CHE-1012258]Chlorophenyl-stabilized platinum nanoparticles (1.85 nm) exhibited electrocatalytic activity for oxygen reduction up to 3 times higher than that of commercial Pt/C catalysts. Similar enhancement was observed with naked Pt/C functionalized by the same chlorophenyl fragments, suggesting the important role of organic capping ligands in the manipulation of nanoparticle electrocatalytic performance

Preparation of Dendritic Pt Thin Films and Their Anomalous Infrared Effects

采用方波电位,在10x10-3MOl·l-1k2PTCl6+3x10-4MOl·l-1PbAC2+0.5MOl·l-1HClO4溶液中,于本体PT电极上电沉积制备出枝晶状PT薄膜.随着沉积时间的增加,枝晶长度逐渐由400nM增加到900nM,且枝晶上的小晶粒(--10nM大小)变得密集.根据循环伏安(CV)曲线中氢吸脱附电量可得出PT薄膜具有中等粗糙度(Cr=9-36),且电极表面的粗糙度随着沉积时间增加而增大.观察到PT薄膜上吸附态CO的原位红外光谱具有明显的增强吸收效应,当沉积时间为6MIn时所制得的枝晶PT电极的红外增强效应最大.CO呈现多种谱峰形状,随着沉积时间的增加,谱峰形状依次为左高右低的双极峰(类fAnO红外效应),单极向下(表面增强红外吸收),左高右低的双极峰,单极向上(异常红外效应),左低右高的双极峰和单极向下.这表明纳米材料薄膜所呈现出的特殊红外性能,与纳米材料的尺度和聚集状态等密切相关.所制备的枝晶状PT薄膜有望为深入认识纳米材料的特殊红外性能提供一个良好的模型材料.Dendritic Pt thin films are electrodeposited on bulk Pt electrodes in 10×10 -3 mol · L -1 K 2 PtCl 6 +3× 10 -4 mol · L -1 PbAc 2 + 0.5 mol · L -1 HClO 4 using square-wave potential pulses.As the deposition time increases, the length of the Pt dendrites increases from 400 to 900 nm, and the distribution density of Pt nanoparticles (--10 nm), which consist of coiled Pt dendrites, increases greatly.From hydrogen adsorption/ desorption obtained from cyclic voltammograms (CV), the surface of the dendritic Pt thin film electrodes has a relative roughness (C r ), which increases from 9 to 36 as the deposition time increases.Maximum enhanced IR absorption of adsorbed CO (CO ad ) is observed at the deposition time of 6 min.Anomalous infrared effects for CO ad are also seen on the dendritic Pt thin film electrodes.The line shapes of CO ad change with increasing deposition time, in order: bipolar→downward→bipolar→upward→bipolar→ downward bands.Fano-like infrared effects (bipolar), surface enhanced IR absorption (enhanced downward band), and abnormal IR effects (enhanced upward band) are highly dependent on the surface architecture of the nanostructures.The as-prepared dendritic Pt thin films provide model substrates for in-depth studies of the anomalous infrared effects of CO ad in metal nanostructures.国家自然科学基金(21073152;20933004;20833005;21021002);福建省高校杰出青年科研人才培育计划(JA10003)资助项目---