将动态应变应用于固定在伪弹性镍钛合金上的薄氧化物薄膜
Summary
动态拉伸应变应用于TiO2 薄膜上，研究应变对电催化的影响，特别是质子还原和水氧化。TiO2 薄膜通过伪弹性镍钛（Nitinol）的热处理来制作。
Abstract
通过应变直接改变材料结构/功能是一个不断增长的研究领域，使材料的新特性的出现。通过控制强加于材料的外部力和诱导应力应变反应（即施加动态应变），可以调整材料 结构。电活性薄膜通常沉积在形状或体积可调弹性基材上，其中机械载荷（即压缩或张力）可以通过施加的应变影响薄膜结构和功能。在这里，我们总结了通过伪弹性镍钛合金（Nitinol）的热处理准备的n型掺杂二氧化钛（TiO2）薄膜的应变方法。所述方法的主要目的是研究应变如何影响金属氧化物的电催化活性，特别是氢演化和氧进化反应。同一系统可以适应更广泛地研究应变的影响。应变工程可用于材料功能的优化，以及外部应力控制下的可调多功能（光）电催化材料的设计。
Introduction
通过引入应变来改变催化材料表面反应的能力已得到广泛认可，1、2、3。1,2,3晶体材料中应变的影响可以通过调整材料结构（静态应变）或施加可变static strain外力（动态应变）来引入。在晶体材料中，静态应变可以通过掺杂4、去合金5、6、,6退火7、外延生长在不匹配的晶体晶格2或大小约束22、3中引入3。在多晶材料中，由于晶体结对8，应变可能发生在晶粒边界内。使用材料结构确定静态应变的最佳程度需要为每个离散应变级别设计一个新样本，这既耗时又昂贵。此外，引入静态应变往往引入化学或配体效应9,9，10，使得分离菌株的贡献变得困难。应用由外力精确控制的动态应变允许系统地调整材料的结构/功能关系，以便在不引入其他效果的情况下探索应变空间的动态范围。
为了研究动态应变对电催化的影响，金属或金属氧化物沉积在弹性形状或体积可调基材,上，如有机聚合物11、12、13、14、1511,12或13,14,15合金16、17。,17机械、热负荷或电气负载的应用会导致弹性基板的弯曲、压缩、伸长或膨胀，进一步导致沉积催化材料的应力应变响应。迄今为止，利用动态应变的催化剂工程对各种金属和半导体材料的电催化活性进行调调。例如：i）2上的氢演化反应 （HER）， Au， Pt， Ni， Cu， WC11，,12，,13，,14，ii） 氮气演进反应 （OER） 在 Niox16上， 镍铁合金18和 iii） 在 Pt 上减氧反应 （ORR）， Pd12，15， 19，,19,20。,在大多数这些报告中，有机聚合物，如聚甲基甲基丙烯酸酯（PMMA），被用作弹性基板。我们之前演示了弹性金属基板的应用，如不锈钢16和超弹性/形状记忆NiTi合金（Nitinol17，21）用于17,21应变研究。Nitinol还被用作用于用于 ORR19的铂薄膜沉积和电池阴极材料沉积的弹性基板，用于储能22、23,23。由于其形状记忆和伪弹性特性，NiTi合金可以通过分别应用中热19或机械应变17来变形。与有机弹性基板相比，金属基材通常不需要粘附促进剂沉积，导电性高，易于功能化。尼蒂诺被用作不锈钢 （SS） 更具弹性的替代品。虽然SS可以可可逆应变至0.2%，但硝酸盐可可可逆应变至7%。Nitinol其独特的特性归功于马腾西固态晶体的变换，它允许大弹性变形24，25。24,这两种材料都以不同的几何形状（例如，箔、电线和弹簧）在商业上提供。当形成弹性弹簧时，金属基板可用于研究动态应变对电催化的影响，而无需昂贵的仪器16;然而，与其他几何形状一样，定义应力应变响应更具挑战性。
在以往利用过渡金属催化剂进行的实验研究中，受压力催化表面活性的变化归因于d轨道的电能变化，俗称d波段理论26。相比之下，应变对金属氧化物的影响要复杂得多，因为它会影响带状gap、载体移动性、扩散和缺陷分布，甚至直接/间接过渡21、27、28、29、30、31。,27,28,29,30,31在这里，我们提供详细的协议，用于制备和表征n型掺杂TiO2薄膜，以及研究这些薄膜在可调、拉伸应变下的电催化活动的协议。等效系统可应用于研究不同材料的电催化活动，作为动态应变的函数。
Protocol
Representative Results
Discussion
镍醇是一种合适的弹性基板，用于在薄膜上施加机械应力。它是市售的，高导电性，可以很容易地功能化。制备红十二金TiO 2薄膜，通过热处理硝基醇，导致高n型掺杂TiO2。2必须强调，NiTi/TiO2是一个独特的系统，其中 TiO2薄膜通过 NiTi 的热处理而不是沉积方法进行准备。我们以前的出版物已经表明，适用于NiTi/TiO2的应变主要影响氧气空缺的分布、扩散和能?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
这项工作由所有合著者、可持续能源联盟有限责任公司的员工、美国能源部国家可再生能源实验室的经理和运营商根据第1号合同进行。DE-AC36-08GO28308。由美国能源部、科学办公室、基础能源科学办公室、化学科学司、地球科学和生物科学、太阳能光化学项目提供的资金。
Materials
| 2-Propanol | Sigma Aldrich | 109634 | |
| Ag/AgCl (3M NaCl) Reference Electrode | BASi | MF-2052 | |
| Alkaline Reference Electrode | Basi | EF-1369 | |
| Ethyl alcohol, Pure, 200 proof, anhydrous, =99.5% | Sigma Aldrich | 459836 | |
| MT I I / F u l l am SEMTester Series | MTI Instruments | ||
| Nitinol foil, 0.05mm (0.002in) thick, superelastic, flat annealed, pickled surface | Alfa Aesar | 45492 | |
| PK-4 Electrode Polishing Kit | BASi | MF-2060 | |
| Potentiostat 600D | CHI instruments | 600D | |
| Pt wire | Sigma Aldrich | 267228-1G | |
| Sodium hydroxide | Sigma Aldrich | 221465 | |
| Sulfuric acid | Sigma Aldrich | 30743 |
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