Water oxidation is the prerequisite for dioxygen evolution in natural or artificial photosynthesis. Although it has been demonstrated that multinuclear active sites are commonly necessary for water oxidation, as inspired by the natural oxygen-evolving centre CaMn₄O₅, a multinuclear manganese cluster, whether mononuclear manganese can also efficiently catalyse water oxidation has been a long-standing question. Herein, we found that a heterogeneous catalyst with mononuclear manganese embedded in nitrogen-doped graphene (Mn-NG) shows a turnover frequency as high as 214 s⁻¹ for chemical water oxidation and an electrochemical overpotential as low as 337 mV at a current density of 10 mA cm⁻². Structural characterization and density functional theory calculations reveal that the high activity of Mn-NG can be attributed to the mononuclear manganese ion coordinated with four nitrogen atoms embedded in the graphene matrix.

水的氧化是自然或人工光合作用中产生双氧的先决条件。尽管已经证明了多核活性位点通常是水氧化所必需的，但受自然放氧中心CaMn ₄ O ₅（一种多核锰簇）的启发，单核锰是否也能有效催化水氧化一直是一个由来已久的问题。问题。在本文中，我们发现在氮掺杂石墨烯（Mn-NG）中嵌入单核锰的非均相催化剂在化学反应中的化学水氧化显示出高达214 s ^-1的周转频率，在电流密度下的电化学超电势低至337 mV 10 mA cm ^-2的。结构表征和密度泛函理论计算表明，Mn-NG的高活性可归因于与嵌入石墨烯基质中的四个氮原子配位的单核锰离子。