Schmuecker Samantha M, Clouser Dale, Kraus Theodore J, Leonard Brian M
Department of Chemistry, University of Wyoming, Laramie, Wyoming, USA.
Dalton Trans. 2017 Oct 10;46(39):13524-13530. doi: 10.1039/c7dt01404j.
Transition metal carbides including chromium, molybdenum, and tungsten are of particular interest as renewable energy catalysts due to their low cost and abundance. While several single metal carbide systems form multiple phases with different compositions and crystal structures, most of these materials are not as well studied due to their limited synthetic approaches and instability. By taking advantage of a low temperature salt flux synthetic method, these unique phases can be more easily synthesized and separated as phase pure materials. As an example, Chromium carbide forms five different crystal structures including three common phases, CrC, CrC, and CrC, and two less studied phases, CrC and CrC. All five compounds were synthesized using the salt flux method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrocatalytic testing for the hydrogen evolution reaction (HER). This low temperature method allows for routine access to multiple compounds in complex phase diagrams and separation of each phase synthetically. This represents a significant step forward in synthesizing rare phases like rocksalt CrC and hexagonal CrC and allows for investigation into their potential catalytic properties and future applications.
包括铬、钼和钨在内的过渡金属碳化物因其低成本和高丰度而作为可再生能源催化剂备受关注。虽然几种单一金属碳化物体系会形成具有不同组成和晶体结构的多个相，但由于其合成方法有限且不稳定，这些材料大多未得到充分研究。通过利用低温盐熔合成法，可以更轻松地合成这些独特的相并将其分离为纯相材料。例如，碳化铬形成五种不同的晶体结构，包括三个常见相CrC、CrC和CrC，以及两个研究较少的相CrC和CrC。所有这五种化合物均采用盐熔法合成，并通过X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）以及析氢反应（HER）的电催化测试进行表征。这种低温方法使得能够常规获取复杂相图中的多种化合物，并通过合成方式分离每个相。这代表了在合成诸如岩盐型CrC和六方型CrC等稀有相方面向前迈出的重要一步，并有助于研究它们潜在的催化性能和未来应用。
