Atomic layer confined vacancies for atomic-level insights into carbon dioxide electroreduction.
Atomic layer confined vacancies for atomic-level insights into carbon dioxide electroreduction.
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原子层限制空位以原子水平洞察二氧化碳电还原
DOI：
10.1038/ncomms14503
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发表时间：
2017-02-21
影响因子：
16.6
通讯作者：
Xie Y
中科院分区：
文献类型：
--
作者：
Gao S;Sun Z;Liu W;Jiao X;Zu X;Hu Q;Sun Y;Yao T;Zhang W;Wei S;Xie Y
氧空位在二氧化碳电还原中的作用仍不清楚。本文以人工合成的缺氧钴氧化物单胞层为例，建立了氧空位局限于原子层的模型。密度泛函理论计算表明，主要缺陷是氧（II）空位，而X射线吸收精细结构光谱揭示了它们不同的氧空位浓度。质子转移在理论上/实验上被证明是一个限速步骤，而能量计算揭示了氧（II）空位的存在通过稳定甲酸根阴离子自由基中间体将限速活化势垒从0.51降低到0.40 eV，这通过将起始电位从0.81降低到0.78 V和将塔菲尔斜率从48 mV dec−1降低到37 mV dec−1得到证实。因此，富空位的钴氧化物单单元电池层表现出2.7 mA cm-2的电流密度，其中约在40小时的测试中，甲酸盐选择性为85%。这项工作建立了一个明确的原子水平的氧空位和二氧化碳电还原之间的相关性。
The role of oxygen vacancies in carbon dioxide electroreduction remains somewhat unclear. Here we construct a model of oxygen vacancies confined in atomic layer, taking the synthetic oxygen-deficient cobalt oxide single-unit-cell layers as an example. Density functional theory calculations demonstrate the main defect is the oxygen(II) vacancy, while X-ray absorption fine structure spectroscopy reveals their distinct oxygen vacancy concentrations. Proton transfer is theoretically/experimentally demonstrated to be a rate-limiting step, while energy calculations unveil that the presence of oxygen(II) vacancies lower the rate-limiting activation barrier from 0.51 to 0.40 eV via stabilizing the formate anion radical intermediate, confirmed by the lowered onset potential from 0.81 to 0.78 V and decreased Tafel slope from 48 to 37 mV dec−1. Hence, vacancy-rich cobalt oxide single-unit-cell layers exhibit current densities of 2.7 mA cm−2with ca. 85% formate selectivity during 40-h tests. This work establishes a clear atomic-level correlation between oxygen vacancies and carbon dioxide electroreduction.