Collaborative Research: Solar-Driven Hydrogenation of CO2 using Hierarchically Porous TiO2 with Spatially Isolated Au and Pt Nanoparticles

利用太阳能从二氧化碳(CO2)中生产甲醇等燃料，有可能将暂时可用的太阳能以化学燃料的形式储存起来，用于运输和其他应用。高效、低成本地生产太阳能燃料仍然是一个科学和技术挑战，存在效率、成本和材料耐用性等问题。这一合作项目旨在设计能够将二氧化碳和氢气转化为甲醇的创新材料，利用自然阳光作为唯一的能源输入。这类材料将由多个组件组成，包括两种类型的金属纳米催化剂，它们分别放置在催化剂系统的多孔纳米结构中。通过收集光线，其中一个金属纳米粒子催化剂将产生热电子和热电子来激活二氧化碳分子。另一种金属催化剂将氢分子分解成氢原子，这也是将二氧化碳转化为甲醇所需的氢原子。通过该项目获得的成果将为利用太阳能实现二氧化碳低温转化为液体燃料提供基本的见解和实用的指导方针。这项研究将纳入高中教师和学生的外展活动以及本科生的暑期研究活动。将为新英格兰地区的当地高中生和K-12科学教师设计和提供关于纳米科学和清洁能源的研讨会。在二氧化碳利用的方法中，利用二氢作为电子供体和质子源将二氧化碳还原为高价值燃料的加氢方法因其可持续性和对环境的低影响而特别令人感兴趣。然而，二氧化碳的加氢通常需要在高温下操作，因为即使在催化剂存在的情况下，也需要大量的能量输入来激活二氧化碳。这项合作的重点是设计一种新型的分级混合光催化剂，可以利用可见光在室温下调解二氧化碳的加氢反应。本项目的第一个目标是合成由多孔二氧化钛和空间隔离的金和铂纳米颗粒组成的杂化光催化剂。等离子体金纳米粒子将获得可见光，随后将光子转换为热能，并产生热电子以激活二氧化碳。铂纳米颗粒将促进氢的吸附和解离。本项目的第二个目标是研究复合光催化剂在协同催化二氧化碳活化和氢气溢出以实现二氧化碳的太阳能加氢方面的作用。将利用原位红外光谱进行机理研究，以建立杂化材料的纳米结构与其催化性能之间的关联。使用这些复合光催化剂的太阳能驱动加氢的结果将展示一种利用可再生能源将二氧化碳转化为液体燃料的新途径。

Solar-powered production of fuels such as methanol from carbon dioxide (CO2) offers the potential to enable solar power, which is available on a transient basis, to be stored in the form of a chemical fuel for transport and other applications. Efficient and cost-effective production of solar fuels remains a scientific and technological challenge with issues of efficiency, cost, and materials durability. This collaborative project aims to design innovative materials that are capable of converting carbon dioxide and hydrogen to methanol using natural sunlight as the only energy input. This class of materials will consist of multiple components, including two types of metal nanoparticle catalysts that are separately placed within porous nanostructures of the catalyst system. By harvesting light, one of the metal nanoparticle catalyst will produce both heat and hot electrons to activate the carbon dioxide molecules. The other metal catalyst will split hydrogen molecules into hydrogen atoms, which are also needed for converting carbon dioxide to methanol. Results obtained through this project will offer fundamental insights and practical guidelines to achieving low-temperature conversion of carbon dioxide to liquid fuels using solar energy. The research will be incorporated into outreach activities for high school teachers and students as well as summer research activities for undergraduate students. Workshops on nanoscience and clean energy will be designed and offered to local high school students and K-12 science teachers in the New England area. Among the methods for carbon dioxide utilization, hydrogenation which employs dihydrogen as an electron donor and proton source to reduce carbon dioxide to high-value fuels is of particular interest, due to its sustainability and low environmental impact. Hydrogenation of carbon dioxide, however, often requires operation at high temperature because a large energy input is needed to activate carbon dioxide, even in the presence of catalysts. The focus of this collaborative effort is to design a new class of hierarchical hybrid photocatalysts that can harness visible light to mediate hydrogenation of carbon dioxide at room temperature. The first objective of this project is to synthesize hybrid photocatalysts consisting of porous titanium dioxides and spatially isolated nanoparticles of Au and Pt. The plasmonic Au nanoparticles will harvest visible light and subsequently convert photons to thermal energy and generate hot electrons for carbon dioxide activation. The Pt nanoparticles will facilitate hydrogen adsorption and dissociation. The second objective of this project is to investigate the hybrid photocatalysts in cooperatively catalyzing carbon dioxide activation and hydrogen spillover to achieve solar hydrogenation of carbon dioxide. Mechanistic studies using in situ infrared spectroscopic studies will be conducted to establish correlations between nanostructures of the hybrid materials and their catalytic performance. The outcome of solar-driven hydrogenation using these hybrid photocatalysts will illustrate a new pathway to convert carbon dioxide to liquid fuels by utilizing renewable energy sources.