Phase Exploration and Identification of Multinary Transition-Metal Selenides as High-Efficiency Oxygen Evolution Electrocatalysts through Combinatorial Electrodeposition
Phase Exploration and Identification of Multinary Transition-Metal Selenides as High-Efficiency Oxygen Evolution Electrocatalysts through Combinatorial Electrodeposition
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DOI：
10.1021/acscatal.8b01977
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发表时间：
2018-09-01
期刊：
影响因子：
12.9
通讯作者：
Nath, Manashi
中科院分区：
文献类型：
--
作者：
Cao, Xi;Hong, Yu;Nath, Manashi
设计用于水氧化的高效电催化剂已经成为催化界中越来越重要的概念，因为它在清洁能源的产生和储存中具有重要意义。在这方面，过渡金属掺杂的混合金属硒化物结合地球丰富的元素，如Ni和Fe引起了人们的注意，由于他们意想不到的高的电催化活性，对析氧反应（OER）与低过电位在碱性介质中。本文通过对Ni-Fe-Co三元体系相图的研究，采用组合电沉积法制备了Ni-Fe-Co四元混合金属硒化物复合材料。测量所得的四元和三元混合金属硒化物组合物的OER电催化活性，以系统地研究催化活性随催化剂组合物变化的趋势。因此，鉴定了对四元Fe-Co-Ni混合金属硒化物表现出最佳催化效率的组合物。据观察，在该Ni-Fe-Co相空间中，四元硒化物优于二元以及三元金属硒化物。通过能量色散谱（EDS）和X射线光电子能谱（XPS）确定了催化剂膜中元素的组成和相对丰度。OER催化活性作为催化剂组成的函数的绘图表明，在具有中等量的Ni和痕量的Co掺杂的富Fe区域中，催化效率更显著，并且（Ni0.25Fe0.68Co0.07）（3）Se-4表现出最佳性能，其在10 mA cm（-2）下显示出230 mV（相对于RHE）的过电位，对于连续氧气生成稳定性超过8小时。还观察到，典型地，四元金属硒化物组成接近AB（2）Se（4），其显示尖晶石结构类型。电化学测量沿着与密度泛函理论（DFT）计算进行关联的催化活性的增强向富铁区域与组合物。采用第一性原理密度泛函理论计算了不同组成的混合金属硒化物表面的羟基吸附能。该吸附能可直接与OER活性的起始相关，并且结果与实验观察到的起始过电位趋势非常匹配。了解催化活性随组成变化的趋势对于通过目标材料合成进行催化剂设计非常重要。这项工作代表了一个系统的四元金属硒化物相探索的一个例子，并提供了一个强大的基础，可以扩展到研究其他混合金属硒化物组合。
Designing high-efficiency electrocatalysts for water oxidation has become an increasingly important concept in the catalysis community due to its implications in clean energy generation and storage. In this respect transition metal-doped mixed-metal selenides incorporating earth abundant elements such as Ni and Fe have attracted attention due to their unexpectedly high electrocatalytic activity toward the oxygen evolution reaction (OER) with low overpotential in alkaline medium. In this article, quaternary mixed-metal selenide compositions incorporating Ni-Fe-Co were investigated through combinatorial electrodeposition by exploring the ternary phase diagram of Ni-Fe-Co systems. The OER electrocatalytic activity of the resultant quaternary and ternary mixed metal selenide compositions was measured in order to systematically investigate the trend of catalytic activity as a function of catalyst composition. Accordingly, the composition(s) exhibiting the best catalytic efficiency for the quaternary Fe-Co-Ni mixed-metal selenide was identified. It was observed that the quaternary selenide outperformed the binary as well as the ternary metal selenides in this Ni-Fe-Co phase space. The elemental composition and relative abundance of the elements in the catalyst film was ascertained from energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Mapping of the OER catalytic activity as a function of catalyst composition indicated that catalytic efficiency was more pronounced in the Fe rich region with moderate amounts of Ni and trace amounts of Co doping, and the best performance was exhibited by (Ni0.25Fe0.68Co0.07)(3)Se-4, which showed an overpotential of 230 mV (vs RHE) at 10 mA cm(-2) with stability exceeding 8 h for continuous oxygen generation. It was also observed that typically the quaternary metal selenide composition was close to AB(2)Se(4), which shows a spinel structure type. Electrochemical measurements along with density functional theory (DFT) calculations were performed to correlate the enhancement of catalytic activity toward the Fe-rich region with composition. First principles DFT calculations were used to estimate the hydroxyl adsorption energy (E-ads) on the surface of the mixed-metal selenides with varying compositions. This adsorption energy could be directly correlated to the onset of OER activity, and the results matched very well with the experimentally observed trend with respect to onset overpotential. The knowledge of the trend of catalytic activity as a function of composition will be very important for catalyst design through targeted material synthesis. This work represents an example of a systematic phase exploration for quaternary metal selenides and provides a strong foundation which can be expanded to study other mixed-metal selenide combinations.