School of Optical and Electronic Information, Huazhong University of Science and Technology , Wuhan 430074, PR China.
ACS Appl Mater Interfaces. 2017 May 10;9(18):15364-15372. doi: 10.1021/acsami.7b00019. Epub 2017 Apr 28.
Low-cost and highly efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are intensively investigated for overall water splitting. Herein, we combined experimental research with first-principles calculations based on density functional theory (DFT) to engineer the NiCoS@NiFe LDH heterostructure interface for enhancing overall water-splitting activity. The DFT calculations exhibit strong interaction and charge transfer between NiCoS and NiFe LDH, which change the interfacial electronic structure and surface reactivity. The calculated chemisorption free energy of hydroxide (ΔE) is reduced from 1.56 eV for pure NiFe LDH to 1.03 eV for the heterostructures, indicating a dramatic improvement in OER performance, while the chemisorption free energy of hydrogen (ΔE) maintains almost invariable. By the use of the facile hydrothermal method, NiCoS nanotubes, NiFe LDH nanosheets, and NiCoS@NiFe LDH heterostructures are prepared on nickel foam, of which the corresponding experimental OER overpotentials are 306, 260, and 201 mV at 60 mA cm, respectively. These results are good agreement with the theoretical predictions. Meanwhile, the HER performance has little improvement, with an overpotential of about 200 mV at 10 mA cm. Due to the dramatic improvement in OER performance, there was an enhancement in the overall water-splitting activity of the NiCoS@NiFe LDH heterostructures, with a low voltage of 1.6 V.
用于析氢反应 (HER) 和析氧反应 (OER) 的低成本、高效双功能电催化剂被广泛研究用于整体水分解。在此，我们结合实验研究和基于密度泛函理论 (DFT) 的第一性原理计算，对 NiCoS@NiFe LDH 异质结构界面进行了工程设计，以增强整体水分解活性。DFT 计算表明 NiCoS 和 NiFe LDH 之间存在强烈的相互作用和电荷转移，这改变了界面电子结构和表面反应性。计算得到的氢氧化物化学吸附自由能 (ΔE) 从纯 NiFe LDH 的 1.56 eV 降低到异质结构的 1.03 eV，表明 OER 性能有了显著提高，而氢的化学吸附自由能 (ΔE) 几乎保持不变。通过使用简便的水热法，在镍泡沫上制备了 NiCoS 纳米管、NiFe LDH 纳米片和 NiCoS@NiFe LDH 异质结构，相应的实验 OER 过电位分别为 60 mA cm 时为 306、260 和 201 mV。这些结果与理论预测吻合较好。同时，HER 性能略有提高，在 10 mA cm 时的过电位约为 200 mV。由于 OER 性能的显著提高，NiCoS@NiFe LDH 异质结构的整体水分解活性得到增强，在 1.6 V 的低电压下即可实现。
