无氧条件下黄铁矿表面的羟基化与自氧化

Hydroxylation and self-oxidation of pyrite surfaces under anaerobic conditions

过去20年里,无氧条件下黄铁矿–水界面产生活性氧是黄铁矿表面反应性的重要发现之一。这一反应不仅对现代环境有重要影响,而且在早期地球环境演化中也扮演着重要角色。无氧条件下黄铁矿–水界面产生的活性氧具有极强的氧化性,理论上有氧化黄铁矿自身的能力。然而,无氧条件下黄铁矿–水界面产生的活性氧对其自身是否有氧化作用(即黄铁矿自氧化)及其反应机制还不得而知。本研究采用原位漫反射红外傅里叶变换光谱(in-situDRIFTS)和准原位X射线光电子能谱(quasi-in-situXPS)结合密度泛函理论(DFT)计算,探究了无氧条件下黄铁矿–水界面的自氧化初始反应过程。结果表明:(1)无氧条件下黄铁矿–水界面会发生自氧化反应,生成高价态的硫物种和铁氧化物;(2)黄铁矿–水界面的自氧化反应伴随着羟基的生成和消耗;(3)黄铁矿–水界面的羟基源于水分子在黄铁矿表面缺陷位点的解离作用,可为活性氧的产生提供物源。这些发现不仅揭示了黄铁矿–水界面的羟基化和自氧化过程,还为深入理解黄铁矿–水界面反应在早期地球环境演化中的重要作用提供了认知基础。

The generation of reactive oxygen species(ROS) at pyrite-water interface under anoxic conditions has been one of the important discoveries in surface reactivity of pyrite during the past 20 years. This reaction not only has an important influence on modern environments but has also played an important role in the evolution of the early Earth. Under anoxic conditions, the ROS produced at pyrite-water interface is a type of strong oxidants and theoretically has the ability to oxidize pyrite. However, the fact that the ROS produced at the pyrite-water interface can oxidize pyrite itself(i.e., self-oxidation of pyrite) has been overlooked. To reveal this reaction process, we used in-situ diffuse infrared Fourier transform spectroscopy(DRIFTS), quasi in-situ X-ray photoelectron spectroscopy(XPS), and density functional theory(DFT) calculations to study the initial reaction processes of the self-oxidation of pyrite under anaerobic conditions. The results indicated that:(1) self-oxidation of pyrite occurs at pyrite-water interface under anaerobic conditions, resulting in the formation of high-valent sulfur species and iron oxides;(2) the self-oxidation reaction at pyrite-water interface is accompanied by the formation and consumption of interfacial hydroxyl groups;and(3) the hydroxyl groups at the pyrite-water interface are derived from the dissociation of water molecules at the defective sites on pyrite and could be a source for ROS. These findings revealed the hydroxylation and self-oxidation processes of pyrite surfaces, providing a fundamental understanding of the importance of the reactions at the pyrite-water interface in the evolution of early Earth.