Biogenic Transition Metal Oxides as Water-Oxidation Electrocatalysts

生物过渡金属氧化物作为水氧化电催化剂获得了化学系化学催化计划的这一奖项，加州大学戴维斯分校的R.David Britt教授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。某些细菌使用一种酶来产生一种锰氧化物材料，布里特和他的同事已经证明，这种材料可以分解水，这是利用太阳光的能量制造廉价太阳能燃料的关键步骤。布里特实验室正在不同的条件下生产这种材料，并探索这种酶的突变体的活性，以优化锰氧化物材料的水分解活性。他们的目标是制造一种廉价的生物材料，使用地球上丰富的锰来取代现有的基于昂贵稀有金属的催化剂。与该研究项目相关的外展活动包括在高中和大学层面的暑期研究机会，通过向学生介绍与可再生能源和环境问题相关的有趣的化学和生物界面来激励他们。自然选择了一个离散的氧化锰(MnOx)单元作为放氧催化剂--所有产氧光合体中发现的Mn4O5Ca放氧复合体(OEC)。受OEC的启发，人们合成了许多锰络合物和纳米颗粒，并将其作为水氧化反应的催化剂进行了研究。在加州大学戴维斯分校R.David Britt教授的实验室里，一种多铜氧化酶(MCO)酶Mnx在大气O2的氧化电位的驱动下氧化水中的Mn(II)，为以完全生物的方式生成MnOx材料提供了一种方便的方法。Mnx酶的生物活性使布里特实验室能够系统地改变所产生的MnOx的结构和组成，并测试哪些因素能产生最高的活性。具体而言，本项目主要围绕以下三个方面展开。1)探讨Mnx催化氧化Mn(II)的分子机理。2)利用多种技术(高场EPR、XAS、SEM等)对生物生成的MnOx进行表征，并将其用作水氧化电催化剂，建立构效关系。3)生物金属/混合金属氧化物催化剂：可以通过轴向配体的定点突变来调节Mnx酶中第一类铜的还原电位。因此，底物的类型可以扩大(如Fe(II)、Co(II)或Ni(II))，可以产生金属/混合金属氧化物并作为水氧化电催化剂进行测试。该项目在培训研究生和本科生甚至来访的高中生方面产生了广泛的影响，涉及过渡金属配位化学、生物化学、电化学和光谱学，并被整合到布里特教授每年教授的以能源为重点的化学讲座中。

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.