Piezopotential-Driven Redox Reactions at the Surface of Piezoelectric Materials
Piezopotential-Driven Redox Reactions at the Surface of Piezoelectric Materials
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DOI：
10.1002/anie.201201424
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发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Wang, Xudong
中科院分区：
文献类型：
--
作者：
Starr, Matthew B.;Shi, Jian;Wang, Xudong
操纵载流子传导特性是控制基于电化学原理的光伏、催化和其他能量转换系统的运行和效率的关键属性。[1-9]这种操纵通常是通过外部电源施加电势梯度和/或通过异质结界面工程产生电子态不连续来完成的。例如，在电化学系统中，跨化学相的电荷传输由不同相内电子态的能量和密度以及所述相之间的任何现有偏置来控制。16.长期以来，压电材料一直被用作偏置和机械位移的来源，这依赖于它们在传感器、致动器、[18]和能量收集器中的机电耦合特性。[19-22]与这一历史先例相反，现代半导体异质结构中的压电材料集成利用了压电势操纵载流子的能力(即，压电学)。[23-27]例如，最近在氧化锌纳米材料中研究了对压电元件进行应变以改变其半导体性能。29]这为应变选通逻辑操作和微电子电路元件的新可能性打开了大门。压电光电化学电池中的应变效应也被证明通过操纵界面能量学而导致性能增强。[30]原则上，电荷载流子能量学的压电调制应该延伸到迄今所探索的埋藏电子界面的边界之外，从而允许直接增强或抑制在压电材料和溶液的界面上发生的电化学过程(即，压电催化)。初步实验表明，机械搅拌的BaTiO_3和ZnO压电微结构在水溶液中发生了H2和O2的析出。[31]为了解释这一有趣的压电催化现象，我们报道了在材料表面的电极上发生的压电势驱动的电化学析氢过程的系统研究。这一结果与预期的压电性和电化学性组合的总体趋势是一致的。析氢速率取决于压电材料的振荡频率和振幅，符合直接压电效应和电化学反应的组合。在密封室中对单晶铁电Pb(Mg1/3Nb2/3)O_3-32PbTiO_3(PMN-PT)悬臂梁的压电催化效应进行了研究(见支持信息中的图S1)。PMN-PT板的电压输出首先在空气中进行了表征(图1a)。悬臂梁以固定的频率和幅度进行机械振动。当压电悬臂梁过渡到去离子水环境时，电压幅值降低，而机械振荡频率和幅值保持不变。为了将整个压电催化系统包含在一个有凝聚力的实体中，构建了一个类似的电路(图1b)。在该电路中，压电材料的相对和反复交替的一侧分别充当工作电极和反电极。应变的压电材料可以被认为是充电的电容器，因此测量电压的变化与…的变化相关
The manipulation of charge-carrier conduction characteristics is a critical attribute governing the operation and efficiency of photovoltaic, catalytic, and other energy-converting systems that are based on electrochemical principles.[1–9] This manipulation is often accomplished through the application of electrical-potential gradients by an external power supply and/or the creation of electronic-state discontinuities by heterojunction-interface engineering.[10–14] For example, in electrochemical systems, the transport of charge across chemical phases is governed by the energy and density of electronic states within the disparate phases as well as any existing bias between said phases.[15, 16] Piezoelectric materials have long been used as a source of bias and mechanical displacement, relying on their mechanical to electrical coupling character for applications in sensors,[17] actuators,[18] and energy harvesters.[19–22] In contrast to this historical precedent, contemporary integration of piezoelectric materials in semiconductor heterostructures capitalizes on the capability of the piezoelectric potential to manipulate charge carriers (ie, piezotronics).[23–27] For instance, the straining of a piezoelectric element in order to change its semiconducting properties has recently been investigated in zinc oxide nanomaterials,[28, 29] which have opened the doors to strain-gated logic operations and new possibilities for microelectronic circuitry elements. Straining effects in piezoelectric photoelectrochemical cells have also been shown to result in performance enhancements through manipulation of interface energetics.[30] In principle, the piezoelectric modulation of charge carrier energetics should extend beyond the bounds of the buried electronic interfaces explored to date, thus allowing the direct enhancement or suppression of electrochemical processes that occur at the interface of a piezoelectric material and a solution (ie, piezocatalysis). Preliminary experiments have shown an evolution of H2 and O2 from mechanically agitated piezoelectric BaTiO3 and ZnO microstructures in an aqueous sonication bath.[31] In order to elucidate the intriguing piezocatalytic phenomenon, we report a systematic study of the piezoelectric-potentialdriven electrochemical H2 evolution process that takes place at the electrodes located on the surface of the material. The results compliment the general trends expected from the combinatorial assemblage of piezoelectricity and electrochemistry. The H2 evolution rates were dependent upon the oscillation frequency and amplitude of the piezoelectric material, in accordance with the combination of the direct piezoelectric effect and electrochemical reactions. A study of the piezocatalytic effect was conducted on a single-crystalline ferroelectric Pb (Mg1/3Nb2/3) O3-32PbTiO3 (PMN-PT) cantilever in a sealed chamber (see Figure S1 in the Supporting Information). The voltage output of the PMN-PT slab was first characterized in air (Figure 1a). The cantilever was mechanically oscillated with a fixed frequency and amplitude. When the piezoelectric cantilever was transitioned to the deionized water environment, the voltage amplitude decreased while the mechanical oscillation frequency and amplitude remained constant. In order to encompass the entire piezocatalytic system into a cohesive entity, an analogous circuit was constructed (Figure 1b). In this circuit, opposite and iteratively alternating sides of the piezoelectric material serve as both the working and counter electrodes, respectively. A strained piezoelectric material can be considered a charged capacitor, and thus the change in measured voltage is correlated with a change in …