Semiconductor/Mixed-Conducting-Oxide Heterojunction for Photo-electrochemical H2O & CO2 Splitting at Elevated Temperatures

PI: Chueh， william提案编号：1336835机构：斯坦福大学标题：高温下光电化学H2O和CO2分裂的半导体/混合导电-氧化物异质结使太阳能在需要的时间和地点可用对提高其利用率至关重要。将蒸汽和/或二氧化碳分解成化学燃料是储存太阳能的一种很有前途的途径。这项工作的目标是设计一种新型的光电电化学电池，利用全固态设计，在500至700摄氏度而不是室温下工作。利用由半导体光吸收剂和混合氧离子和电子导电氧化物组成的氧化物异质结，光吸收剂带隙上下入射的太阳能转化为热能，从而提高太阳能-燃料效率。与传统的基于光伏的方法不同，这里的太阳能转化为燃料的效率随着温度的升高而增加，而不是降低。由氧化物如铁、钒和钛氧化物组成的薄膜异质结将评估其在高温光电化学水和二氧化碳分解中的潜力。具体目标是确定一种材料的组合，这种材料可以提供数千小时的高太阳能-燃料效率和可靠性。本研究的核心部分是理解和控制在半导体氧化物和混合离子和电子导电氧化物之间的异质结在明显高于环境温度下的电荷产生、分离和重组。在涉及氧化物的光电化学中，离子缺陷（如空位）必须发挥重要作用，但尚未得到很好的理解。通过结合快速材料筛选、光电电化学和原位同步加速器x射线表征氧化物异质结，本研究旨在了解极端条件下不同固体交界处的界面化学和电子性质。这项研究旨在提高在化学键中储存间歇性太阳能的可行性，并增加太阳能的全球利用。除了能源产生和存储，对异质结电荷传输的深入了解将有利于催化和高温电子等科学领域，以及极端环境下固体氧化物燃料电池和传感器等应用。项目工作还为一名研究生在项目期间提供研究机会。除了将研究结果纳入本科和研究生课程外，PI还将开发一个独特的“天黑后的太阳”推广项目。人类与阳光的互动是日常生活中最普遍的现象之一，也是提高学生对科学和工程兴趣的绝佳途径。

PI: Chueh, WilliamProposal Number: 1336835Institution: Stanford UniversityTitle: Semiconductor/Mixed-Conducting-Oxide Heterojunction for Photo-electrochemical H2O and CO2 Splitting at Elevated TemperaturesMaking solar energy available when and where it is required is crucial towards increasing its utilization. Dissociating steam and/or carbon dioxide to chemical fuels is a promising route for storing solar energy. The objective of this work is to design a new class of photo-electrochemical cells that operates at 500 to 700 deg. C rather than at room temperature by utilizing an all solid-state design. Using an oxide heterojunction consisting of a semiconducting light absorber and a mixed oxygen ion and electron conducting oxide, incident solar energy above and below the band gap of the light absorber is converted to thermal energy, which in turn increases the solar-to-fuel efficiency. Unlike conventional photovoltaic-based approaches, here the solar-to-fuel efficiency increases, rather than decreases, with temperature. Thin-film heterojunctions consisting of oxides such as iron, vanadium, and titanium oxides will be evaluated for their potential in elevated temperature photo-electrochemical water and carbon dioxide splitting. The specific objective is to identify a combination of materials that delivers high solar-to-fuel efficiency and reliability over thousands of hours.The central component of this research is understanding and controlling charge generation, separation, and recombination at the heterojunction between a semiconducting oxide and a mixed ionic and electronic conducting oxide, at temperatures significantly above ambient. In photo-electrochemistry involving oxides, ionic defects such as vacancies must play an important role, yet it is not well understood. By combining rapid material screening, opto-electrochemical and in-situ synchrotron X-ray characterizations of oxide heterojunctions, this research aims to understand the interfacial chemistry and electronic properties at the junction of dissimilar solids under extreme conditions.This research seeks to enhance the viability of storing intermittent solar energy in chemical bonds, and increase the global utilization of solar energy. Beyond energy generation and storage, advanced understanding of charge transport at heterojunctions will benefit scientific fields such as catalysis and high temperature electronics, and applications such as solid-oxide fuel cells and sensors in extreme environments. The project work also provides research opportunities for one graduate student over the duration of the project. In addition to incorporating the results into undergraduate and graduate curriculums, the PI will develop a unique "Solar After Dark" outreach program. Human interaction with sunlight is one of the most ubiquitous phenomena in daily life and is an excellent vehicle to raise student interest in science and engineering.