Akbari Nader, Nandy Subhajit, Chae Keun Hwa, Najafpour Mohammad Mahdi
Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran.
Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea.
Langmuir. 2023 Aug 22;39(33):11807-11818. doi: 10.1021/acs.langmuir.3c01540. Epub 2023 Aug 9.
An efficient and durable oxygen evolution reaction (OER) catalyst is necessary for the water-splitting process toward energy conversion. The OER through water oxidation reactions could provide electrons for HO, CO, and N reduction and produce valuable compounds. Herein, the FeNi (1:1 Ni/Fe) alloy as foam, after anodizing at 50 V in a two-electrode system in KOH solution (1.0 M), was characterized by Raman spectroscopy, diffuse reflectance spectroscopy (DRS), X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), high-angle annular dark-field imaging (HAADF)-scanning transmission electron microscopy (STEM) and used as an efficient and durable OER electrocatalyst in KOH solution (1.0 M). The overpotential for the onset of the OER based on extrapolation of the Tafel plot was 225 mV. The overpotentials for the current densities of 10 and 30 mA/cm are observed at 270 and 290 mV, respectively. In addition, a low Tafel slope is observed, 38.0 mV per decade, for the OER. To investigate the mechanism of the OER, surface-enhanced Raman spectroscopy was used to detect FeNi hydroxide and characteristic peaks of HO. Impurities in KOH can adsorb onto the electrode surface during the OER. Peaks corresponding to Ni(III) (hydr)oxide and FeO can be detected during the OER, but high-valent FeNi (hydr)oxides are unstable and reduce under the open circle potential. Metal hydroxide transformations during the OER and anion adsorption should be carefully considered. In addition, FeO may convert to γ-FeO during the OER. This study aims to offer logical perspectives on the dynamic changes that occur during the OER under alkaline conditions in an anodized FeNi alloy. These changes encompass variations in morphology, surface oxidation, the generation of high-valent species, and phase conversion during the OER.
高效且耐用的析氧反应（OER）催化剂对于水分解过程实现能量转换是必不可少的。通过水氧化反应进行的OER可为HO、CO和N还原提供电子，并产生有价值的化合物。在此，以泡沫形式存在的FeNi（Ni/Fe比例为1:1）合金，在KOH溶液（1.0 M）中于两电极体系中50 V阳极氧化后，通过拉曼光谱、漫反射光谱（DRS）、X射线吸收光谱（XAS）、X射线衍射（XRD）、扫描电子显微镜（SEM）、能量色散X射线光谱（EDX）、透射电子显微镜（TEM）、高角度环形暗场成像（HAADF）-扫描透射电子显微镜（STEM）进行了表征，并用作KOH溶液（1.0 M）中高效且耐用的OER电催化剂。基于塔菲尔曲线外推法得到的OER起始过电位为225 mV。在电流密度为10和30 mA/cm²时观察到的过电位分别为270和290 mV。此外，观察到OER的塔菲尔斜率较低，为每十倍38.0 mV。为了研究OER的机理，采用表面增强拉曼光谱检测氢氧化铁镍和HO的特征峰。在OER过程中，KOH中的杂质会吸附到电极表面。在OER过程中可检测到与Ni(III)（氢）氧化物和FeO对应的峰，但高价FeNi（氢）氧化物不稳定，在开路电位下会还原。OER过程中的金属氢氧化物转变和阴离子吸附应仔细考虑。此外，在OER过程中FeO可能会转化为γ-FeO。本研究旨在对阳极氧化FeNi合金在碱性条件下OER过程中发生的动态变化提供合理的观点。这些变化包括OER过程中的形态变化、表面氧化、高价物种的生成和相转变。
