EAGER: Collaborative Research: Hybrid Quantum Dot-Metal Nanocrystals for Photoreduction of CO2: Synthesis, Spectroscopy and Catalysis

将燃烧产生的二氧化碳与燃料和化学品进行高效、可持续和经济的反应仍然是我们这个时代的主要技术挑战之一。在可持续技术中，由催化材料加速的太阳能直接转化为化学能是最具吸引力的选择之一，但受到太阳能转化为化学能的效率的限制。该项目将研究催化材料的新组合，以及构建这些材料的方法，这些材料有可能进一步提高太阳能驱动的二氧化碳反应的速度和效率。该研究还利用了一种超快光谱技术，可以为能量转换过程提供新的思路，这种知识可以扩展到光催化以外的广泛应用。该项目将产生洞察力，支持对我们国家未来能源安全至关重要的技术，同时减少碳排放。能源可持续性和环境保护迫切需要开发新的方法，有效地、有选择地、可持续地将二氧化碳转化为有价值的化学品和燃料。在现有的技术中，太阳能驱动的光还原和二氧化碳转化为碳基燃料是一种有吸引力的方法，因为它的可持续性和对环境的影响最小。高性能光催化剂是实现有效CO2光还原的关键。该合作项目将对基于半导体core@shell量子点（QDs，例如CdSe@CdS）和金（Au）纳米粒子（NPs）的混合体的太阳能驱动二氧化碳光还原的新型纳米催化剂进行原理验证研究。CdSe@CdS核壳量子点由于具有1.9 eV的低带隙和高还原导带，可以在整个紫外和大部分可见光光谱范围内有效捕获太阳能。同时，Au NPs具有较高的CO2结合亲和力和良好的反应选择性（如CO2到CO）。通过直接外延生长将CdSe@CdS半导体量子点与Au NPs耦合，有可能大大提高太阳能到化学燃料的整体转换效率。为此，该项目将探索新的合成方法，以合成量子点金属杂化纳米材料，精确控制尺寸，形状，几何形状和晶格应变。独特的HNC结构使得通过超快瞬态吸收光谱定量检测到的高效转移多个电子成为可能，从而为QD-Au之间的结构参数与电荷分离/转移过程之间的关系以及QD-Au的光催化性能提供了基本的理解。除了这个项目的技术方面，这两位研究者还将在两所大学合作组织年度活动，比如以纳米科学和清洁能源为主题的研讨会和推广日。外展活动旨在激发高中学生追求stem相关高等教育的兴趣。此外，还将组织科学研讨会，以突出与光催化二氧化碳还原有关的研究机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Efficient, sustainable, and cost-effective reaction of combustion-generated carbon dioxide to fuels and chemicals remains one of the leading technical challenges of our times. Among sustainable technologies, the direct conversion of solar energy to chemical energy, as accelerated by catalytic materials, is one of the most attractive options, but is limited by the efficiency of the solar-to-chemical energy conversion. The project will investigate a new combination of catalytic materials, and methods for structuring those materials, that has potential to further increase both the rate and efficiency of solar-driven carbon dioxide reactions. The study also utilizes an ultrafast spectroscopic technique that may shed new light on the energy conversion process - knowledge that can be extended to a wide range of applications beyond photocatalysis. The project will generate insight that supports technologies critical to our nation's future energy security while decreasing carbon emissions.Energy sustainability and environmental protection has created an urgent need to develop new methods that efficiently, selectively, and sustainably convert carbon dioxide (CO2) into valuable chemicals and fuels. Among existing technologies, solar-driven photoreduction and transformation of CO2 into carbon-based fuels represents an attractive method due to its sustainability and its minimal environmental impact. High-performance photocatalysts are the key to achieving effective CO2 photoreduction. The collaborative project will perform proof-of-principle studies of novel nanocatalysts for solar-driven CO2 photoreduction based on hybrids of semiconductor core@shell quantum dots (QDs, e.g., CdSe@CdS) and gold (Au) nanoparticles (NPs). CdSe@CdS core-shell QDs can efficiently capture solar energy in the entire ultraviolet and most of the visible spectral range due to their low bandgap of 1.9 eV as well as having a highly reductive conduction band. Meanwhile, Au NPs show high CO2 binding affinity and excellent reaction selectivity (e.g., CO2 to CO). Coupling CdSe@CdS semiconductor QDs with Au NPs through direct epitaxial growth has the potential to greatly improve the overall conversion efficiency of solar energy to chemical fuels. To this end, the project will explore new synthetic methods towards synthesizing QD-metal hybrid nanomaterials with precise control over size, shape, geometry, and lattice strain. The unique HNC structures make it possible to efficiently transfer multiple electrons as quantitatively detected by ultrafast transient absorption spectroscopy, thereby providing fundamental understanding of the relationships between structural parameters and charge separation/transfer processes between the QDs and Au, as well as photocatalytic performance of QD-Au. Beyond the technical aspects of the project, the investigators will collaborate in organizing annual events such as workshops and outreach days featuring nanoscience and clean energy at both universities. The outreach activities will be designed to stimulate the interests of students from high schools in pursing STEM-related higher education. In addition, scientific symposia will be organized with the goal of highlighting research opportunities related to photocatalytic CO2 reduction.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.