Biogenic Transition Metal Oxides as Water-Oxidation Electrocatalysts

生物源过渡金属氧化物作为水氧化电催化剂。加州大学戴维斯分校的R. David Britt教授获得了化学部化学催化项目的奖项，他正在研究一种新型的生物催化剂，这将有助于清洁和可再生能源技术。某些细菌利用一种酶产生一种氧化锰材料，布里特和同事已经证明这种材料可以分解水，这是利用太阳能制造廉价太阳能燃料的关键一步。布里特实验室正在不同条件下生产这种材料，并探索这种酶突变体的活性，以优化氧化锰材料的水分解活性。目标是制造一种廉价的生物材料，利用富含地球的锰来取代现有的基于昂贵稀有金属的催化剂。与该研究项目相结合的外展活动包括高中和大学的暑期研究机会，通过向学生介绍与可再生能源和环境问题相关的化学和生物学的有趣界面来激励学生。《自然》杂志选择了一种分立的氧化锰（MnOx）单元作为O2进化的催化剂——在所有的含氧光合生物中都存在的Mn4O5Ca进化氧复合体（OEC）。受OEC的启发，许多锰配合物和纳米颗粒作为水氧化反应的催化剂被合成和研究。在加州大学戴维斯分校的R. David Britt教授实验室的这个项目中，一种多铜氧化酶（MCO）， Mnx，在大气O2的氧化电位的驱动下氧化水中的Mn(II)，提供了一种以完全生物方式生成MnOx材料的方便方法。Mnx酶的生物反应性使布里特实验室能够系统地改变生成的MnOx的结构和组成，并测试哪些因素会产生最高的活性。具体来说，本项目主要集中在以下三个方面。1)探索mnx催化Mn（II）氧化的分子机理。2)通过多种技术（高场EPR、XAS、SEM等）对合成的生物源MnOx形态进行表征，并将各种形态作为水氧化电催化剂，建立构效关系。3)生物源性金属/混合金属氧化物作为催化剂：1型Cu在Mnx酶中的还原电位可以通过轴向配体的定点诱变来调节。因此，衬底的类型可以拓宽(例如Fe(II), Co（II）或Ni(II))，并且可以生成金属/混合金属氧化物并作为水氧化电催化剂进行测试。该项目对过渡金属配位化学、生物化学、电化学和光谱学的研究生和本科生甚至访问高中生的培训具有广泛的影响，并被纳入布里特教授每年教授的以能源为重点的化学课程中。

Biogenic Transition Metal Oxides as Water-Oxidation Electrocatalysts.With this award from the Chemical Catalysis Program of the Chemistry Division, Professor R. David Britt of the University of California at Davis is studying a novel type of biological catalyst which will contribute to clean and renewable energy technology. Certain bacteria use an enzyme to generate a manganese oxide material which Britt and coworkers have shown can split water, a key step in making inexpensive solar fuels, using energy from sunlight. The Britt lab is producing this material under different conditions, and exploring the activity of mutants of this enzyme, to optimize the water splitting activity of the manganese oxide material. The goal is to make an inexpensive bio-material using earth abundant manganese to replace existing catalysts based on expensive rare metals. Outreach activities coupled to this research program include summer research opportunities at both the high school and college level, motivating students by introducing them to this interesting interface of chemistry and biology that is relevant to renewable energy and environmental issues.A discrete manganese oxide (MnOx) unit was selected by Nature as the catalyst for O2 evolution - the Mn4O5Ca oxygen-evolving-complex (OEC) found in all oxygenic photosynthetic organisms. Inspired by the OEC, many manganese complexes and nanoparticles have been synthesized and investigated as catalysts for water-oxidation reaction. In this project in the laboratory of Professor R. David Britt of the University of California at Davis, a multicopper oxidase (MCO) enzyme, Mnx, which oxidizes aqueous Mn(II) driven by the oxidation potential of atmospheric O2, is offering a convenient means to generate a MnOx material in a fully biological fashion. The biological reactivity of the Mnx enzyme is allowing the Britt lab to systematically vary the structure and composition of the resulting MnOx and test what factors give rise to the highest activities. Specifically, this project is focusing on the following three aspects. 1) To explore the molecular mechanism of Mnx-catalyzed Mn(II) oxidation. 2) To characterize the resultant biogenic MnOx forms by multiple techniques (high-field EPR, XAS, SEM, etc) and employ the varied forms as water-oxidation electrocatalysts, in order to establish a structure-activity relationship. 3) Biogenic metal/mixed-metal oxides as catalysts: the reduction potential of type 1 Cu in Mnx enzyme can be tuned through site-directed mutagenesis of the axial ligand. Therefore, the type of substrates may be broadened (e.g. Fe(II), Co(II) or Ni(II)) and metal/mixed-metal oxides may be generated and tested as water-oxidation electrocatalysts. The project has broad impacts in training graduate and undergraduate and even visiting high school students in transition metal coordination chemistry, biochemistry, electrochemistry, and spectroscopy, and is being integrated into energy focused chemistry lectures that Professor Britt teaches each year.