The photogeochemical cycle of Mn oxides on the Earth's surface
The photogeochemical cycle of Mn oxides on the Earth's surface
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地球表面锰氧化物的光地球化学循环
DOI：
10.1180/mgm.2021.10
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发表时间：
2021
影响因子：
2.7
通讯作者：
Changqiu Wang
中科院分区：
文献类型：
--
作者：
Anhuai Lu;Yan Li;Feifei Liu;Yuwei Liu;Huan Ye;Ziyi Zhuang;Yanzhang Li;Hongrui Ding;Changqiu Wang
摘要锰氧化物在大氧化事件之前就已普遍存在于地球上，锰循环是地球表面最重要的地球化学过程之一。在阳光照射的自然环境中，已经发现Mn氧化物的光化学能够在地质和生物系统中实现太阳能的收集和转换。最广泛的锰氧化物之一是水钠锰矿，它是一种半导体层状矿物，在自然界中积极驱动锰的光化学循环。生物光系统II（PSII）中的放氧中心也是Mn 4CaO 5的Mn簇，其在光催化放氧过程中转变为水钠锰矿样结构。这一现象在有机和无机世界之间绘制了Mn功能化光反应的潜在平行。Mn光氧化还原循环涉及Mn（II）的光氧化和Mn（IV/III）氧化物的光还原溶解。在自然界中，Mn（IV/III）光还原的发生通常伴随着天然有机物的氧化降解。对于Mn（II）氧化成Mn氧化物，已经提出了由微生物（例如恶臭假单胞菌和芽孢杆菌属物种）介导的生物催化和由半导体矿物或活性氧物种介导的非生物光反应的机制。特别是，厌氧Mn（II）光氧化过程已被实验证明，这揭示了锰氧化物出现在地球上的大气氧化之前。本文综述了自然界中锰氧化物光氧化还原循环的最新研究进展，并对广泛存在于地球表面的半导体锰氧化物的光化学性质进行了全新的探讨。
Abstract Manganese (Mn) oxides have been prevalent on Earth since before the Great Oxidation Event and the Mn cycle is one of the most important biogeochemical processes on the Earth's surface. In sunlit natural environments, the photochemistry of Mn oxides has been discovered to enable solar energy harvesting and conversion in both geological and biological systems. One of the most widespread Mn oxides is birnessite, which is a semiconducting layered mineral that actively drives Mn photochemical cycling in Nature. The oxygen-evolving centre in biological photosystem II (PSII) is also a Mn-cluster of Mn4CaO5, which transforms into a birnessite-like structure during the photocatalytic oxygen evolution process. This phenomenon draws the potential parallel of Mn-functioned photoreactions between the organic and inorganic world. The Mn photoredox cycling involves both the photo-oxidation of Mn(II) and the photoreductive dissolution of Mn(IV/III) oxides. In Nature, the occurrence of Mn(IV/III) photoreduction is usually accompanied with the oxidative degradation of natural organics. For Mn(II) oxidation into Mn oxides, mechanisms of biological catalysis mediated by microorganisms (such as Pseudomonas putida and Bacillus species) and abiotic photoreactions by semiconducting minerals or reactive oxygen species have both been proposed. In particular, anaerobic Mn(II) photo-oxidation processes have been demonstrated experimentally, which shed light on Mn oxide emergence before atmospheric oxygenation on Earth. This review provides a comprehensive and up-to-date elaboration of Mn oxide photoredox cycling in Nature, and gives brand-new insight into the photochemical properties of semiconducting Mn oxides widespread on the Earth's surface.