EAGER: Reduction of Carbon Dioxide to Methane

通过催化转化二氧化碳实现燃料的可持续生产是一个研究领域，它有可能加强国家能源安全，同时提供一种机制，最大限度地减少二氧化碳的直接排放。以前关于二氧化碳光还原为燃料的研究都使用了基于二氧化钛的催化剂。利用二氧化钛作为光催化剂进行二氧化碳光还原的一个主要挑战是通过光照射形成的电子-空穴对的快速复合。需要电子才能通过二氧化碳的还原产生产物。最大限度地减少电荷复合对于增强产品形成至关重要。尽管过去使用金属和非金属改性剂对二氧化钛催化剂进行了改性，但公布的数据显示，有用产品的产率相对较低。典型的产品包括CO和有价值的燃料产品，如CH4和CH3OH。几种催化剂导致了多种产物的形成，导致在实际应用中需要气体分离技术。亚利桑那州立大学让·安迪诺教授的实验室初步实验表明，RGO-TiO2、还原石墨氧化物和二氧化钛的复合催化剂是有希望的。当光激活二氧化钛时，RGO可能有助于最大限度地减少电荷复合，从而使更多的电子可用于表面二氧化碳还原反应。使用还原氧化石墨的一个潜在挑战是，层间间距是否足以使二氧化钛驻留在RGO层之间。增加层间距的改进的RGO结构将缓解这一担忧。此外，如果与碳氢化合物相比，RGO的改性剂能够选择性地吸引二氧化碳，那么这可能允许增强功能性。已公布的数据表明，离子液体对二氧化碳有很强的吸引力。Andino假设离子液体(IL)功能化的RGO-TiO2会吸引二氧化碳，在TiO2光还原反应中产生足够的电荷分离(使电子可用于CO2光还原反应)，并拒绝产生的碳氢化合物，如CH4，从而减少分离需要。Andino已经进行了初步工作，以合成IL-RGO/TiO2光催化剂，并测试该催化剂在水蒸气存在下将CO2还原为碳氢化合物的性能。结果表明，在无CO存在的条件下，IL-RGO/TiO2光催化剂能够快速、选择性地生成CH4。二氧化碳光还原产生甲烷的速率是任何其他研究小组发表的结果的30多倍。结果(结合文献数据)表明，新开发的IL-RGO/Ti02催化剂产生CH4的速度远远优于现有的任何其他催化剂。这是获得这一热切奖项的理想基础。研究人员通常使用GC技术来量化数据，而不是使用漂移红外光谱技术。此外，需要知道氧气存在对产品产量的影响。拟议的EIGER奖将提供必要的数据来证实观察结果，并产生额外的数据来支持全面调查。这一EARGER预计将在催化领域产生几个更广泛的影响，并将扩大该领域的参与。首先，将产生的数据将有助于确定IL-RGO/Ti02催化剂在直接和选择性地产生有价值的燃料(CH4)方面的有用性。这项工作可能会对国家能源安全和控制二氧化碳排放产生重大影响。拟议的项目将部分用于资助两名传统上代表性不足的化学工程研究生。参与这个与社会联系紧密的项目的经历如何？S的宏大挑战已经激励了这些学生，并有望帮助他们在科学和工程领域留住他们。预计这两名学生将取得足够的进展，以便至少提交一篇同行评议的论文，并在当地以及2013年美国化学学会、美国化学工程师学会或空气与废物管理协会的年度会议上发表演讲。

Sustainable generation of fuels through the catalytic conversion of CO2 is an area of research that has the potential to enhance national energy security while simultaneously providing a mechanism to minimize direct CO2 emissions. Previous studies on CO2 photoreduction to fuels have utilized TiO2-based catalysts. A major challenge that exists with utilizing TiO2 as a photocatalyst for CO2 photoreduction is the fast recombination of electron-hole pairs which are formed by light irradiation. Electrons are needed to generate products via reduction of CO2. Efforts to minimize charge recombination are critical for enhancing product formation. Despite past efforts at modifying the TiO2-based catalysts using both metal and non-metal modifiers, published data shows relatively low production rates for useful products. Typical products include CO and valuable fuel products such as CH4 and CH3OH. Several of the catalysts resulted in the formation of multiple products, resulting in the need for gas separation technologies when the catalyst is implemented in a real-world scenario.Preliminary experiments in the laboratories of Professor Jean Andino at Arizona State University have shown promise for a composite catalyst of RGO-TiO2, reduced graphite oxide and titania. The RGO can potentially assist in minimizing charge recombination when TiO2 is activated by light, thereby making more electrons available for a surface CO2 reduction reaction. A potential challenge with using reduced graphite oxide is whether the interlayer spacing would be sufficient to allow TiO2 to reside between the RGO layers. A modified RGO structure with increased interlayer spacing would alleviate this concern. Moreover, if the modifier for the RGO is capable of selectively attracting CO2 as compared to hydrocarbons, then this may allow for enhanced functionality. Published data show that CO2 is strongly attracted to ionic liquids. Andino hypothesizes that an ionic liquid (IL) functionalized RGO-TiO2 would result in the attraction of CO2, sufficient charge separation within the TiO2 (making electrons available for the CO2 photoreduction reaction), and rejection of the produced hydrocarbons, such as CH4, thus reducing separation needs.Andino has performed preliminary work to synthesize the IL-RGO/TiO2 catalyst and to test the characteristics of the catalyst for the reduction of CO2 to hydrocarbons in the presence of water vapor. The DRIFTS studies showed the IL-RGO/TiO2 catalyst appears to lead to the selective and fast formation of CH4 in the absence of any CO. The CH4 production rate from CO2 photoreduction is more than 30 times higher than that which was published by any other research group. The results (taken in conjunction with literature data) suggest that the newly developed IL-RGO/TiO2 catalyst produces CH4 at a rate that is far superior to any other existing catalyst.This is an ideal basis for this EAGER award. Researchers typically use GC techniques to quantify the data and not the DRIFTS IR spectroscopy technique. Furthermore the impact of oxygen presence on product yield needs to be known. The proposed EAGER award will provide the necessary data to confirm the observation and generate additional data to support a full investigation.This EAGER is expected to have several broader impacts in the catalysis area and will broaden participation in the field. First, the data that will be generated will help to establish the usefulness of the IL-RGO/TiO2 catalyst in the direct and selective generation of a valuable fuel (CH4). This work could have significant impacts in the areas of national energy security and the control of CO2 emissions. The proposed project would be used to partially fund two traditionally underrepresented chemical engineering graduate students. The experience of working on the proposed project that has a strong connection to society?s grand challenges has already inspired these students, and is expected to help retain them in science and engineering. The expectation is that both students will make sufficient progress so that at least one peer-reviewed paper will be submitted and presentations made locally and also at annual meetings of either the American Chemical Society, the American Institute of Chemical Engineers, or the Air and Waste Management Association in 2013.