Direct high-resolution mapping of electrocatalytic activity of semi-two-dimensional catalysts with single-edge sensitivity
Direct high-resolution mapping of electrocatalytic activity of semi-two-dimensional catalysts with single-edge sensitivity
复制标题
DOI：
10.1073/pnas.1821091116
复制
发表时间：
2019-06-11
影响因子：
11.1
通讯作者：
Xin, Huolin L.
中科院分区：
文献类型：
--
作者：
Sun, Tong;Wang, Dengchao;Xin, Huolin L.
低维电催化剂的催化活性高度依赖于它们的局部原子结构，特别是那些在边缘和角落发现的不太协调的位点；因此，以真正的纳米级分辨率直接探测特定局部位置的电催化电流变得至关重要。尽管操作成像工具的可用性不断增加，但迄今为止，还不可能测量单个材料边缘的电催化活性并将其与局部结构缺陷直接关联起来。在此，我们展示了使用扫描电化学显微镜（SECM）的反馈和生成/收集操作模式以 15 nm 空间分辨率独立成像形貌和局部电催化活性的可能性。我们采用这种操作显微镜技术来绘制半二维氧化镍纳米片的析氧活性。分辨率和灵敏度的提高使我们能够区分材料边缘的较高活性和操作中完全协调的表面的活性。空间分辨电化学信息与最先进的电子断层扫描相结合，揭示了边缘的 3D 复杂性，而从头计算使我们能够揭示半 2D 材料各个边缘上复杂的协调依赖活动，这是其他方法无法实现的。模拟线扫描与实验数据的比较表明，纳米片边缘的催化电流密度比 NiO 基面的催化电流密度高约 200 倍。
The catalytic activity of low-dimensional electrocatalysts is highly dependent on their local atomic structures, particularly those less-coordinated sites found at edges and corners; therefore, a direct probe of the electrocatalytic current at specified local sites with true nanoscopic resolution has become critically important. Despite the growing availability of operando imaging tools, to date it has not been possible to measure the electrocatalytic activities from individual material edges and directly correlate those with the local structural defects. Herein, we show the possibility of using feedback and generation/collection modes of operation of the scanning electro-chemical microscope (SECM) to independently image the topography and local electrocatalytic activity with 15-nm spatial resolution. We employed this operando microscopy technique to map out the oxygen evolution activity of a semi-2D nickel oxide nanosheet. The improved resolution and sensitivity enables us to distinguish the higher activities of the materials' edges from that of the fully coordinated surfaces in operando. The combination of spatially resolved electro-chemical information with state-of-the-art electron tomography, that unravels the 3D complexity of the edges, and ab initio calculations allows us to reveal the intricate coordination dependent activity along individual edges of the semi-2D material that is not achievable by other methods. The comparison of the simulated line scans to the experimental data suggests that the catalytic current density at the nanosheet edge is similar to 200 times higher than that at the NiO basal plane.