Coupling and Spatiotemporal Structure in Electrochemically Reacting Systems

摘要-哈德逊-0000483浓度、温度和电势的时空变化发生在许多反应系统中，包括液相和气相反应、气固非均相反应和生化反应;这种不均匀性对反应的总体速率以及系统动力学有很大影响。 在本研究中，PI计划对电化学反应中的时空模式和反应部位间的耦合进行实验研究，并使用多种技术来研究时空结构。 时间和空间尺度是相互关联的，因为通过势场和浓度场的相互作用，长度尺度通常随着频率的增加而减小。 一些研究将使用电极阵列在反应表面的许多位置独立地测量电流或反应速率。 该方法适用于在大范围的条件下的所有类型的电化学反应，因为在每个电极处以高采样率测量电流。 通过改变阵列中电极的数量、单个电极的尺寸或电极之间的间隔来改变反应表面的长度尺度。 电化学反应通过电场强烈耦合，即，长程耦合对系统特性起着重要作用。 PI计划使用一种新的实验装置来研究金属电溶解反应过程中的全局耦合效应。 通过使用一组单独和集体的外部电阻，他能够改变全局耦合的程度，而不改变系统的其他参数。 将确定对耦合强度的依赖性;将研究从无序（湍流）到有序或相干态的转变以及同步和聚集态的出现。PI还计划研究时间和时空强迫的影响。 这种强制，有时称为电荷调制电场，在诸如多层GMR材料的制造和用于互连技术的过孔的超填充的应用中是有用的。 他将研究在脉冲条件下的铜沉积，重点是由此产生的空间结构。 还将研究使用超短脉冲电压输入的微结构化。 电子器件尺寸的减小导致了对用于制造片上互连的新技术的探索。 他将研究的高频方法可能会大大提高空间分辨率。 此外，电极阵列将用于强迫研究。 他将研究输入到阵列的单个通道的时空混沌的排序。 由于存在许多不稳定的空间模式，这种排序是复杂的，但是这种排序在等离子体、激光设备以及在时间和空间都发生变化的化学和生物系统中是重要的。 最后，他计划研究时间和空间强迫对燃料电池应用中感兴趣的电催化反应的影响，氢和小有机化合物的氧化。 通过使用可寻址的微阵列，PI将研究时间强迫对反应速率的可能影响，可能是通过从表面去除抑制剂，以及不同空间尺度的脉冲输入对激活的影响。

Abstract - Hudson - 0000483Temporal and spatial variations in concentration, temperature, and potential occur in many reacting systems including liquid and gas phase reactions, gas-solid heterogeneous reactions, and biochemical reactions; such nonuniformities can have a strong effect on the overall rate of reaction as well as the system dynamics. In this work, the PI plans to carry out experimental studies on spatiotemporal patterns and coupling among reaction sites during electrochemical reactions.He plans to use several techniques to study the temporal and spatial structures. The time and space scales are interrelated because of interactions through the potential and concentration fields with the length scale generally decreasing with increasing frequency. Some of the studies will be done using arrays of electrodes to measure the current, or rate of reaction, independently at many locations on the reaction surface. The method is applicable to all types of electrochemical reactions over a large range of conditions since the current is measured at each electrode at a high sampling rate. The length scale of the reaction surface is varied by changing the number of electrodes in an array, the size of the individual electrodes, or the spacing among the electrodes. Electrochemical reactions are strongly coupled through the electric field, i.e., long rage coupling plays in important role in the system characteristics. The PI plans to use a novel experimental setup to study the effects of global coupling during metal electrodissolution reactions. Through the use of a set of individual and collective external resistors he is able to vary the degree of global coupling without changing the other parameters of the system. The dependence on coupling strength will be determined; transitions form disordered (turbulent) to ordered or coherent states and the occurrence of synchronized and clustered states will be studied.The PI also plans to study the impact of temporal and spatiotemporal forcing. Such forcing, sometimes called charge modulated electric fields, is useful in applications such as the manufacture of multilayered GMR materials and the superfilling of vias for interconnect technology. He will investigate copper deposition under pulsed conditions with an emphasis on the resulting spatial structure. Microstructuing using ultra-short pulsed voltage inputs will also be investigated. The reduction in size of electronic devices has led to the search for new technologies for the manufacture of on-chip interconnects. The high-frequency methods the he will be investigating may lead to greatly improved spatial resolution. In addition, the electrode arrays will be used in the forcing studies. He will investigate the ordering of spatiotemporal chaos with inputs to a single channel of an array. Such ordering is complicated due to the existence of numerous unstable spatial modes but such ordering is important in plasma, laser devices, and in both chemical and biological systems where variations in both time and space occur. Finally, he plans to look at the effects of temporal and spatial forcing on electrocatalytic reactions of interest in fuel cell applications, the oxidation of hydrogen and of small organic compounds. By using addressable microarrays the PI will investigate the possible influence of temporal forcing on reaction rate, likely through the removal of inhibitors from the surface, and also the effect of the input of impulses of varying spatial scale on activation.