Coupling and Spatiotemporal Structure in Electrochemically Reacting Systems

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，浓度、温度和电势都会发生时空变化；这种不均匀性会对反应的总速率和系统动力学产生强烈的影响。在这项工作中，PI计划对电化学反应过程中反应位点之间的时空模式和耦合进行实验研究。他计划使用几种技术来研究时空结构。由于电位场和浓度场的相互作用，时间尺度和空间尺度是相互关联的，长度尺度一般随频率的增加而减小。一些研究将使用电极阵列来测量电流或反应速率，在反应表面的许多位置独立进行。该方法适用于大范围条件下的所有类型的电化学反应，因为在每个电极上以高采样率测量电流。反应表面的长度尺度可以通过改变阵列中电极的数量、单个电极的大小或电极之间的间距来改变。电化学反应是通过电场进行强耦合的，即长程耦合在体系特性中起着重要作用。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全局耦合的影响。通过使用一组单独的和集体的外部电阻，他能够在不改变系统其他参数的情况下改变全局耦合的程度。确定对耦合强度的依赖关系；从无序（湍流）到有序或相干状态的转变以及同步和聚集状态的发生将被研究。该计划还计划研究时间和时空强迫的影响。这种强迫，有时被称为电荷调制电场，在制造多层GMR材料和互连技术的过孔的超填充等应用中很有用。他将研究脉冲条件下的铜沉积，重点是由此产生的空间结构。使用超短脉冲电压输入的微结构也将被研究。电子设备尺寸的缩小促使人们寻找制造片上互连的新技术。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。他将研究时空混沌的排序与输入到一个阵列的单一通道。由于存在许多不稳定的空间模式，这种排序很复杂，但这种排序在等离子体，激光设备以及发生时间和空间变化的化学和生物系统中都很重要。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，氢的氧化和小有机化合物。通过使用可寻址微阵列，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.