Chen Shichuan, Kang Zhixiong, Zhang Xiaodong, Xie Junfeng, Wang Hui, Shao Wei, Zheng XuSheng, Yan Wensheng, Pan Bicai, Xie Yi
Hefei National Laboratory for Physical Science at the Microscale, CAS Center for Excellence in Nanoscience, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, 230026, P. R. China.
College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan, 250014, P. R. China.
ACS Cent Sci. 2017 Nov 22;3(11):1221-1227. doi: 10.1021/acscentsci.7b00424. Epub 2017 Oct 24.
Identification of active sites in an electrocatalyst is essential for understanding of the mechanism of electrocatalytic water splitting. To be one of the most active oxygen evolution reaction catalysts in alkaline media, Ni-Fe based compounds have attracted tremendous attention, while the role of Ni and Fe sites played has still come under debate. Herein, by taking the pyrrhotite FeS nanosheets with mixed-valence states and metallic conductivity for examples, we illustrate that Fe could be a highly active site for electrocatalytic oxygen evolution. It is shown that the delocalized electrons in the ultrathin FeS nanosheets could facilitate electron transfer processes of the system, where d orbitals of Fe and Fe would be overlapped with each other during the catalytic reactions, rendering the ultrathin FeS nanosheets to be the most efficient Fe-based electrocatalyst for water oxidation. As expected, the ultrathin FeS nanosheets exhibit promising electrocatalytic oxygen evolution activities, with a low overpotential of 0.27 V and a large current density of 300 mA cm at 0.5 V. This work provides solid evidence that Fe could be an efficient active site for electrocatalytic water splitting.
确定电催化剂中的活性位点对于理解电催化水分解的机理至关重要。作为碱性介质中最具活性的析氧反应催化剂之一，镍铁基化合物已引起了极大关注，然而镍和铁位点所起的作用仍存在争议。在此，以具有混合价态和金属导电性的磁黄铁矿FeS纳米片为例，我们阐明铁可能是电催化析氧的高活性位点。结果表明，超薄FeS纳米片中的离域电子可促进体系的电子转移过程，在催化反应过程中，铁的d轨道会相互重叠，使超薄FeS纳米片成为用于水氧化的最有效的铁基电催化剂。正如预期的那样，超薄FeS纳米片表现出有前景的电催化析氧活性，在0.5 V时过电位低至0.27 V，电流密度高达300 mA cm。这项工作提供了确凿的证据，证明铁可能是电催化水分解的有效活性位点。
