Collaborative Research: Bandgap Engineering of Dilute Antimonide III-Nitride Nanostructures for Efficient and Stable Photocatalytic Overall Water Splitting

太阳能是化石燃料等传统能源的可持续替代品。这个项目的重点是利用阳光将水分解成氢和氧，直接使用氢作为燃料，或者进行进一步的化学反应，以产生广泛的燃料和化学品。具体来说，该项目将研究一种新型半导体材料，这种材料有可能显著提高太阳能到燃料的能量转换效率，从而实现更具成本效益的催化剂和能量转换设备。该项目将有助于我们国家的能源安全和未来的能源需求，同时还将建立一支训练有素的劳动力队伍，并为本科生、代表性不足的少数民族和K-12学生提供stem相关的外展服务。该研究将探索稀锑化氮化物，如InGaSbN纳米线，以克服传统光催化剂材料的局限性，在波长高达700 nm的光照下实现光催化整体水分解，这在可再生能源和人工光合作用中仍然是一个巨大的挑战。该研究小组最近在理论和实验上都表明，加入少量锑（Sb）后，GaN的能带隙（约3.4 eV）可以大幅降低到约2 eV。值得注意的是，掺入Sb后氮化镓能隙的减小主要是由于价带边缘的上移，这与与铟（in）合金化后导带边缘的下移形成了直接对比。该项目将从InGaSbN的能带结构、电子、光学和光催化性质的第一性原理计算开始。实验上，预测的纳米级光催化剂组合物将在低成本、大面积的硅衬底上生长，并将使用广泛的技术进行表征。InGaSbN的带隙能量和带边位置将通过独立改变In和Sb掺入量来调节，并将深入研究其在全水分解和半反应中的光催化性能。此外，InGaSbN纳米线的表面将被设计成富氮的，以防止光腐蚀和氧化，目标是实现高效，长期稳定的运行。该项目的成功也将提供理想的1.7 eV顶光吸收剂与Si底光吸收剂配对，以实现高效，低成本，高稳定的光电化学水分解。教育和推广项目包括：1)鼓励未被充分代表的少数民族和女性从事科学和工程职业；2)让本科生参与研究；3)向公众传播研究成果。这个项目将接触到更广泛的公众，特别是在纳米结构材料、催化和太阳能设备等科学和技术方面代表性不足的群体。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。

Energy from the sun offers a sustainable alternative to conventional energy sources such as fossil fuels. This project focuses on using sunlight to split water into hydrogen and oxygen, for direct use of hydrogen as a fuel, or for further chemical reactions to generate a broad range of fuels and chemicals. Specifically, the project will investigate a new class of semiconductor materials that have potential to significantly increase the efficiency of solar-to-fuel energy conversion, thereby achieving more cost-effective catalysts and energy conversion devices. The project will contribute to our Nation's energy security and future energy needs while also building a highly-trained workforce and providing STEM-related outreach to undergraduate students, underrepresented minorities, and K-12 students.The research will explore dilute antimonide nitrides, e.g. InGaSbN nanowires to overcome the limitations of conventional photocatalyst materials for achieving photocatalytic overall water splitting under light illumination up to 700 nm in wavelength, which has remained a grand challenge in renewable energy and in artificial photosynthesis. The research team has recently shown, both theoretically and experimentally, that the energy bandgap (approximately 3.4 eV) of GaN can be substantially reduced to about 2 eV with the incorporation of a small amount of antimony (Sb). Significantly, the reduction of energy bandgap of GaN with Sb incorporation is primarily due to the upward shift of the valence band edge, which is in direct contrast to the downward shift of the conduction band edge by alloying with indium (In). The project will start with first-principles calculations of the energy band structure and electronic, optical and photocatalytic properties of InGaSbN. Experimentally, the predicted nanoscale photocatalyst compositions will be grown on low cost, large area Si substrates, and will be characterized using a broad range of techniques. The bandgap energy and band edge positions of InGaSbN will be tuned by independently varying In and Sb incorporation, and their photocatalytic performance in overall water splitting and half reactions will be thoroughly investigated. In addition, the surfaces of InGaSbN nanowires will be engineered to be nitrogen-rich to protect against photocorrosion and oxidation, with the goal to achieve high efficiency, long-term stable operation. Success of this project will also provide an ideal 1.7 eV top light absorber to pair with a Si bottom light absorber to achieve high efficiency, low cost, and highly stable photoelectrochemical water splitting. The education and outreach program includes 1) encouraging underrepresented minorities and women in careers in science and engineering, 2) involving undergraduate students in research, and 3) communicating the research to the general public. This project will reach out to the broader public, particularly underrepresented groups on the science and technology of nanostructured materials, catalysis, and solar energy devices.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.