Study of adsorption and reaction of functional molecules on Pt single crystal electrodes at atomic and molecular level

纳米材料形状控制合成是制备功能纳米材料、特别是高性能催化剂的重要途径。在纳米材料形状控制合成中，覆盖剂（Citrate、PVP）以及还原剂（抗坏血酸）等功能分子起着决定性的作用，但其调控作用机制亟需深入研究。本论文运用电化学循环伏安（CV）、电化学原位红外光谱（FTIR）和扫描隧道显微镜（STM）等技术研究了纳米材料形状控制合成功能分子在Pt(hkl)和Pd/Pt(hkl)单晶电极表面的吸脱附和反应过程；结合Pt纳米粒子合成，探讨其在纳米材料形状控制合成中的作用机制。主要研究结果如下： 1、研究表明柠檬酸根在Pt单晶电极表面发生特性吸附，在不同晶面上具有不同的吸附行为。在Pt(311)和Pt...Nanoparticles shape controlled synthesis is an important way to prepare functional material, especially for high performance catalyst. The functional molecules as capping agent (Citrate, PVP) and reducing agent (ascorbic acid) play a key role in the synthesis. However, the mechanism of functional molecules is still unclear. The adsorption of functional molecules on Pt(hkl) and Pd/Pt(hkl) electrode...学位：理学博士院系专业：化学化工学院_物理化学学号：2052010015367

Electrocatalytic reduction of CO2 to ethylene and ethanol through hydrogen-assisted C-C coupling over fluorine-modified copper

精准控制C1分子C-C偶联合成特定C2+化合物是C1化学中极具挑战性的难题。由于C2+化合物(如乙烯和乙醇)在化工和能源领域具有重要用途，将CO2直接转化为C2+产物极具吸引力。发展高效催化剂，实现高电流密度、高C2+选择性、高稳定性的“三高”性能，是推进电催化还原CO2走向实际应用的关键。研究团队针对电催化还原CO2中高CO2还原法拉第效率的催化剂常常活性低的问题，提出了适当提高催化剂活化水的能力对增加CO2还原活性的重要性，发展出氢助碳碳偶联(hydrogen-assisted C-C coupling)的新策略，在氟修饰的铜(F-Cu)催化剂上实现了CO2电催化还原制乙烯和乙醇的新突破。该研究工作实验部分主要由王野、张庆红教授指导，能源材料协同创新中心iChEM2016级博士生马文超、固体表面物理化学国家重点实验室高级工程师谢顺吉(共同第一作者)完成；理论计算部分由程俊教授指导，2017级硕士生刘彤彤(共同第一作者)、2016级博士生樊祺源完成。叶进裕博士为原位红外测试提供了支持。上海光源姜政研究员、孙凡飞博士、杨若欧为同步辐射表征提供了支持。 这是投稿的最终版本，正式出版的论文版本请访问官方链接（https://doi.org/10.1038/s41929-020-0450-0）。Electrocatalytic reduction of CO2 into multi-carbon (C2+) products is a highly attractive route for CO2 utilization. However, the yield of C2+ products remains low because of the limited C2+ selectivity at high CO2 conversion rate. Here, we report a fluorine-modified copper catalyst that exhibits an ultrahigh current density of 1.6 A cm−2 at C2+ (mainly ethylene and ethanol) Faradaic efficiency of 80% for electrocatalytic CO2 reduction in a flow cell. The C2-4 selectivity reaches 85.8% at a single-pass yield of 16.5%. We show a hydrogen-assisted C−C coupling mechanism between adsorbed formyl (CHO) intermediates for C2+ formation. Fluorine enhances water activation, CO adsorption and hydrogenation of adsorbed CO to CHO intermediate that can readily undergo coupling. Our findings offer an opportunity to design highly active and selective CO2 electroreduction catalysts with potential for practical applicationThis work was supported by the National Key Research and Development Program of the Ministry of Science and Technology of China (No. 2017YFB0602201), the National Natural Science Foundation of China (Nos. 21690082, 91545203, 21503176 and 21802110), We thank staffs at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facilities (SSRF) for assistance with the EXAFS measurements.研究工作得到科技部重点研发计划（批准号：2017YFB0602201）和国家自然科学基金（批准号：21690082、91545203、21503176、21802110）项目的资助

Studies of oxidation Processes of Adsorbed and Solution CO on Pt(110) Electrode by Cyclic Voltammetry and in situ FTIRS

通讯作者，Tel:(86-592)2181081， E-mail:sgsun@xmu．edu.cn[中文文摘]应用电化学原位傅里叶变换红外反射光谱(in situ FTIRS)研究了酸性介质中Pt(110)单晶电极上吸附态CO(COad)和溶液相CO(COsol)的氧化过程.循环伏安测试表明,COsol氧化的峰电位比COad氧化的正移了168mV,其峰电流密度为后者的6.7倍.电化学原位红外光谱检测到CO主要生成线型的吸附态物种(COL),均匀分布在Pt(110)表面上.当溶液中不存在CO时,COL仅在电位高于0.15V才发生氧化.而且,该谱峰在其稳定吸附的电位区间内随电位增加蓝移,Stark系数为30cm-1·V-1;在COL发生氧化的电位区间,其谱峰强度随电位增加减小、峰位红移,线性变化率为-56cm-1·V-1.溶液中饱和CO时,原位红外光谱在-0.05V即可检测到CO2的存在,显示COL起始氧化的电位提前了200mV;电位高于-0.05V,该谱峰即发生红移,对应的线性变化率为-26.5cm-1·V-1.[英文文摘]The oxidation processes of adsorbed CO (COad) and solution phase CO (COsol) on Pt(110) electrode were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. It has revealed that in comparison with COad on Pt(110) in a CO-free solution,the oxidation current peak of COsol in a CO-saturated solution is positively shifted ca. 168 mV,and the peak current density has been increased by 6.70 times. Linear adsorbed CO (COL)is determined by in-situ FTIR spectroscopy as the main species,which is uniformly distributed on Pt (110) surface． In a CO-free solution， the onset potential of COL is measured by in-situ FTIRS ca．0． 15 V; the COL band is blue-shifted with the increase of electrode potential in the potential range where COL is stable，yielding a Stark tuning rate 30 cm － 1·V － 1 ; when the COL is oxidized at E ＞ 0．15 V，the COL band is red-shifted at a rate of － 56 cm － 1·V － 1 ． In the case of CO-saturated solution， the CO2 band could be appeared in the in-situ FTIR spectrum recorded at － 0．05 V，demonstrating that the onset potential of COL oxidation is negatively shifted ca． 200mV in comparison with Pt(110) in a CO-free solution; the COL band is immediately red-shifted with a rate of－26．5 cm－1·V－1 when the potential is above －0．5 V．国家自然科学基金项目(20833005,20828005,20921120405)资

Studies of oxidation Processes of Adsorbed and Solution CO on Pt(110) Electrode by Cyclic Voltammetry and in situ FTIRS

应用电化学原位傅里叶变换红外反射光谱(In SITu fTIrS)研究了酸性介质中PT(110)单晶电极上吸附态CO(COAd)和溶液相CO(COSOl)的氧化过程.循环伏安测试表明,COSOl氧化的峰电位比COAd氧化的正移了168MV,其峰电流密度为后者的6.7倍.电化学原位红外光谱检测到CO主要生成线型的吸附态物种(COl),均匀分布在PT(110)表面上.当溶液中不存在CO时,COl仅在电位高于0.15V才发生氧化.而且,该谱峰在其稳定吸附的电位区间内随电位增加蓝移,STArk系数为30CM-1·V-1;在COl发生氧化的电位区间,其谱峰强度随电位增加减小、峰位红移,线性变化率为-56CM-1·V-1.溶液中饱和CO时,原位红外光谱在-0.05V即可检测到CO2的存在,显示COl起始氧化的电位提前了200MV;电位高于-0.05V,该谱峰即发生红移,对应的线性变化率为-26.5CM-1·V-1.The oxidation processes of adsorbed CO (COad) and solution phase CO (COsol) on Pt(110) electrode were investigated by cyclic voltammetry and in-situ FTIR spectroscopy.It has revealed that in comparison with COad on Pt(110) in a CO-free solution,the oxidation current peak of COsol in a CO-saturated solution is positively shifted ca.168 mV,and the peak current density has been increased by 6.70 times.Linear adsorbed CO (COL) is determined by in-situ FTIR spectroscopy as the main species,which is uniformly distributed on Pt (110) surface.In a CO-free solution,the onset potential of COL is measured by in-situ FTIRS ca.0.15 V; the COL band is blue-shifted with the increase of electrode potential in the potential range where COL is stable,yielding a Stark tuning rate 30 cm -1·V -1; when the COL is oxidized at E > 0.15 V,the COL band is red-shifted at a rate of - 56 cm -1·V -1.In the case of CO-saturated solution,the CO2 band could be appeared in the in-situ FTIR spectrum recorded at - 0.05 V,demonstrating that the onset potential of COL oxidation is negatively shifted ca.200 mV in comparison with Pt( 110) in a CO-free solution; the COL band is immediately red-shifted with a rate of - 26.5 cm -1·V -1 when the potential is above - 0.05 V.国家自然科学基金项目(20833005;20828005;20921120405)资

Studies of oxidation Processes of Adsorbed and Solution CO on Pt(110) Electrode by Cyclic Voltammetry and in situ FTIRS

应用电化学原位傅里叶变换红外反射光谱(in situ FTIRS)研究了酸性介质中Pt(110)单晶电极上吸附态CO(COad)和溶液相CO(COsol)的氧化过程.循环伏安测试表明,COsol氧化的峰电位比COad氧化的正移了168mV,其峰电流密度为后者的6.7倍.电化学原位红外光谱检测到CO主要生成线型的吸附态物种(COL),均匀分布在Pt(110)表面上.当溶液中不存在CO时,COL仅在电位高于0.15V才发生氧化.而且,该谱峰在其稳定吸附的电位区间内随电位增加蓝移,Stark系数为30cm-1·V-1;在COL发生氧化的电位区间,其谱峰强度随电位增加减小、峰位红移,线性变化率为-56cm-1·V-1.溶液中饱和CO时,原位红外光谱在-0.05V即可检测到CO2的存在,显示COL起始氧化的电位提前了200mV;电位高于-0.05V,该谱峰即发生红移,对应的线性变化率为-26.5cm-1·V-1.The oxidation processes of adsorbed CO (COad) and solution phase CO (COsol) on Pt(110) electrode were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. It has revealed that in comparison with COad on Pt(110) in a CO-free solution,the oxidation current peak of COsol in a CO-saturated solution is positively shifted ca. 168 mV,and the peak current density has been increased by 6. 70 times. Linear adsorbed CO (COL) is determined by in-situ FTIR spectroscopy as the main species,which is uniformly distributed on Pt (110) surface. In a CO-free solution,the onset potential of COL is measured by in-situ FTIRS ca. 0. 15 V; the COL band is blue-shifted with the increase of electrode potential in the potential range where COL is stable,yielding a Stark tuning rate 30 cm -1·V -1; when the COL is oxidized at E > 0. 15 V,the COL band is red-shifted at a rate of - 56 cm -1·V -1. In the case of CO-saturated solution,the CO2 band could be appeared in the in-situ FTIR spectrum recorded at - 0. 05 V,demonstrating that the onset potential of COL oxidation is negatively shifted ca. 200 mV in comparison with Pt( 110) in a CO-free solution; the COL band is immediately red-shifted with a rate of - 26. 5 cm -1·V -1 when the potential is above - 0. 05 V.作者联系地址：厦门大学固体表面物理化学国家重点实验室,化学化工学院化学系,能源研究院;Author's Address: State Key Laboratory of Physical Chemistry of Solid Surfaces,Department of Chemistry, College of Chemistry and Chemical Engineering,School of Energy Research,Xiamen University, Xiamen 361005,Fujian,Chin

Cyclic Voltammetric Studies in Adsorption of Cetyltrimethylammonium Bromide (CTAB) on Au(111) Electrode

本文运用循环伏安方法研究十六烷基三甲基溴化铵(CTAB)在Au(111)电极上的吸附行为. 首次给出CTAB在Au(111)电极上的循环伏安曲线，其0.18 V、0.27 V有两对可逆的特征电流尖峰，均受扩散控制，且与卤素离子种类有关. 研究表明，烷基铵阳离子的吸脱附及吸附层相转变与Au(111)电极表面结构密切相关.Adsorption of cetyltrimethylammonium bromide (CTAB) on Au(111) electrode was investigated by cyclic voltammetry (CV). The results demonstrate that the adsorption of CTAB on Au(111) yields particular CV features. Both the adsorption of CTA+ and the phase change of the surfactant film are surface structure selective. Two pairs of stable sharp peaks that depend on halide species appear upon the adsorption of cationic surfactant on Au(111) electrode. The relationship between the peak current density and the scan rate indicates that the electron transfer reaction was controlled by diffusion process. These CV features are observed for the first time, and reflect the specific interaction between CTAB and Au(111). The results are of significance in understanding the interaction of CTAB with Au surface for shape-control synthesis of Au nanoparticles.国家自然科学基金项目（No. 21229301，No. 21361140374）资助作者联系地址：厦门大学 化学化工学院化学系，固体表面物理化学国家重点实验室，福建 厦门 361005Author's Address: State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005,China通讯作者E-mail：[email protected]