Adak Mrinal Kanti, Basak Hirak Kumar, Chakraborty Biswarup
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
ACS Org Inorg Au. 2023 May 27;3(4):223-232. doi: 10.1021/acsorginorgau.3c00007. eCollection 2023 Aug 2.
Transition metal-based ABO-type materials have now been paid significant attention due to their excellent electrochemical activity. However, a detailed study to understand the active species and its electro-evolution pathway is not traditionally performed. Herein, FeAsO, a bimetallic ABO-type oxide, has been prepared solvothermally. In-depth microscopic and spectroscopic studies showed that the as-synthesized cocoon-like FeAsO microparticles consist of several small individual nanocrystals with a mixture of monoclinic and triclinic phases. While depositing FeAsO on three-dimensional nickel foam (NF), it can show oxygen evolution reaction (OER) in a moderate operating potential. During the electrochemical activation of the FeAsO/NF anode through cyclic voltammetric (CV) cycles prior to the OER study, an exponential increment in the current density () was observed. An ex situ Raman study with the electrode along with field emission scanning electron microscopy imaging showed that the pronounced OER activity with increasing number of CV cycles is associated with a rigorous morphological and chemical change, which is followed by [AsO] leaching from FeAsO. A chronoamperometric study and subsequent spectro- and microscopic analyses of the isolated sample from the electrode show an amorphous γ-FeO(OH) formation at the constant potential condition. The in situ formation of FeO(OH) (ED indicates electrochemically derived) shows better activity compared to pristine FeAsO and independently prepared FeO(OH). Tafel, impedance spectroscopic study, and determination of electrochemical surface area have inferred that the in situ formed FeO(OH) shows better electro-kinetics and possesses higher surface active sites compared to its parent FeAsO. In this study, the electrochemical activity of FeAsO has been correlated with its structural integrity and unravels its electro-activation pathway by characterizing the active species for OER.
基于过渡金属的ABO型材料因其优异的电化学活性而受到了广泛关注。然而，传统上并未对其活性物种及其电演化途径进行详细研究。在此，通过溶剂热法制备了双金属ABO型氧化物FeAsO。深入的显微镜和光谱研究表明，所合成的茧状FeAsO微粒由几个小的单个纳米晶体组成，具有单斜相和三斜相的混合物。当将FeAsO沉积在三维泡沫镍（NF）上时，它在中等工作电位下可表现出析氧反应（OER）。在OER研究之前，通过循环伏安（CV）循环对FeAsO/NF阳极进行电化学活化期间，观察到电流密度（）呈指数增加。对电极进行的非原位拉曼研究以及场发射扫描电子显微镜成像表明，随着CV循环次数的增加，明显的OER活性与严格的形态和化学变化有关，随后是FeAsO中[AsO]的浸出。计时电流研究以及随后对电极分离样品进行的光谱和显微镜分析表明，在恒电位条件下形成了无定形γ-FeO(OH)。原位形成的FeO(OH)（ED表示电化学衍生）比原始FeAsO和独立制备的FeO(OH)表现出更好的活性。塔菲尔、阻抗光谱研究以及电化学表面积的测定推断，原位形成的FeO(OH)与其母体FeAsO相比，表现出更好的电动力学性能并且具有更高的表面活性位点。在本研究中,FeAsO的电化学活性与其结构完整性相关联，并通过表征OER的活性物种揭示了其电活化途径。
