Computational Identification of Perovskite Oxide (PO) Redox Mediators for Solar Thermochemical Hydrogen (STCH) Production

Morelock, Ryan Jackson

Graduate Thesis Or Dissertation

Computational Identification of Perovskite Oxide (PO) Redox Mediators for Solar Thermochemical Hydrogen (STCH) Production Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/n009w383r

Abstract

Environmental and more recent geopolitical concerns surrounding electricity production have reinvigorated the development of clean, homegrown energy technologies. The emphasis on sustainable solutions prioritizes readily available, renewable energy sources to reduce global carbon emissions and foster energy independence. Solar thermochemical hydrogen (STCH) production from water and sunlight offers advantages over non-renewable energy sources like coal and natural gas. These include facile hydrogen chemical storage and distribution, easily scalable facilities that can meet variable energy demands, i.e., from individual homes or neighborhoods to cities or regions, prospects for decentralization that could fortify our national power grid’s security, and the highest theoretical efficiency compared to other water-splitting hydrogen production methods. As a result, STCH production stands out as an incredibly promising alternative energy technology.

Several barriers currently impede the grid-scale viability of STCH production. The direct thermolysis of steam into diatomic hydrogen and oxygen occurs at 2200°C, surpassing the upper thermal stability temperature of most conventional reactor materials (~1500°C). At temperatures less than 1500°C, negligible hydrogen is produced via direct thermolysis. To overcome this challenge, steam dissociation is typically coupled to a metal oxide’s two-step reduction/oxidation cycle, which can produce significant hydrogen well below the thermal stability limit. The metal oxide must have the appropriate properties to produce STCH economically, which include being minimally expensive, having minimal phase degradation and thus not needing to be replaced frequently, and having redox thermodynamics and kinetics that maximize STCH hydrogen production. Although a few known redox mediators demonstrate some of these traits, a single material that satisfies all of these criteria remains elusive. In this thesis, I aim to identify novel metal oxide redox mediators that satisfy these criteria.

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