Copper Cobalt Selenide as a High-Efficiency Bifunctional Electrocatalyst for Overall Water Splitting: Combined Experimental and Theoretical Study
Copper Cobalt Selenide as a High-Efficiency Bifunctional Electrocatalyst for Overall Water Splitting: Combined Experimental and Theoretical Study
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DOI：
10.1021/acsaem.0c00262
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发表时间：
2020-03-23
影响因子：
6.4
通讯作者：
Nath, Manashi
中科院分区：
文献类型：
--
作者：
Cao, Xi;Medvedeva, Julia E.;Nath, Manashi
非贵金属基催化剂用于水的完全裂解，由于其在能量转换装置中的实际应用前景，仍受到一些研究小组的追捧。在这篇文章中，纳米结构的CuCo 2Se 4包含地球丰富的元素已被报道表现出上级的双功能电催化活性的析氧反应（OER）和析氢反应（HER）在碱性条件下。具有尖晶石结构类型的CuCo 2Se 4电催化剂分别需要320 mV的低过电位以达到OER的50 mA cm（-2）电流密度和125 mV以达到HER的10 mA cm（-2）电流密度，这低于其他报道的基于Co/Cu的过渡金属硫属化物电催化剂，并且显著低于众所周知的贵金属氧化物催化剂（IrOx和RuOx）。为了理解CuCo_2Se_4高催化性能的起源，利用密度泛函理论（DFT）研究了CuCo_2Se_4块体以及具有（100）和（111）表面取向的片状物在OH-吸附和无OH-吸附的情况下的结构、电子和磁性.理论计算结果表明，CuCo 2Se 4处于金属状态，具有较高的导电性，这对催化活性起着至关重要的作用。Co和Cu的比较表明，Co位表现出更好的OER催化活性。重要的是，发现Co原子上的局部磁矩的表面增强仅限于（100）板中的顶层，而局部磁矩的这种变化影响（111）板的所有层，强烈地有利于（111）表面处的Co原子上的OH-吸附，并且使得（111）表面更具有催化活性。从DFT研究中还观察到（111）和（100）表面的不同表面能，这将对观察到的这些表面的催化活性具有显著影响。
Nonprecious metal-based catalysts for full water splitting are still being sought after by several groups of researchers, owing to their promising practical application in energy conversion devices. In this article, nanostructured CuCo2Se4 comprising earth-abundant elements have been reported to exhibit superior bifunctional electrocatalytic activity for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions. The CuCo2Se4 electrocatalyst with a spinel structure type requires low overpotential of 320 mV to reach current density of 50 mA cm(-2) for OER and 125 mV to achieve 10 mA cm(-2) for HER, respectively, which is lower than other reported transition metal chalcogenide electrocatalysts based on Co/Cu, and significantly lower than the well-known precious metal oxide catalysts (IrOx and RuOx). To understand the origin of high catalytic performance in CuCo2Se4, density functional theory (DFT) has been utilized to study the structural, electronic, and magnetic properties of bulk CuCo2Se4 as well as slabs with (100) and (111) surface orientations with and without OH- adsorption. The theoretical results show that CuCo2Se4 is in a metallic state with a high electrical conductivity which plays a crucial role in the catalytic activity. Comparison between Co and Cu revealed that Co sites exhibit better OER catalytic activity. Importantly, a surface enhancement of the local magnetic moment on the Co atoms is found to be limited to the top layer in the (100) slab, whereas such variation of the local magnetic moment affects all layers of the (111) slab, strongly favoring OH- adsorption on Co atom at the (111) surface and making the (111) surface more catalytically active. The different surface energies of (111) and (100) surfaces were also observed from DFT studies which will have a pronounced influence on the observed catalytic activity of these surfaces.