Abstract
The University of Central Florida invention helps decrease the overall cost of storing, transporting, and using hydrogen. UCF researchers developed a new electrolyzer design, which introduces a screening gas diffusion layer (GDL). The invention can greatly reduce impurities in the crude feedstock. As a result, hydrogen-containing organic compounds such as methanol can be converted directly into hydrogen, eliminating the need for costly purification steps. Thus, the technology helps to significantly lower hydrogen production costs and carbon intensity.
Though it is an important tool for decarbonization of several sectors, including manufacturing and electric utilities, hydrogen storage and transportation are obstacles to widespread adoption. Hydrogen-containing organic compounds that exist as liquid at ambient temperature and pressure, such as methanol, formic acid, or dimethyl ether, are high-density, low-cost hydrogen carriers more conducive and safer for transportation and storage than hydrogen gas. However, they require conversion to hydrogen gas at the point of use, and thus, the energy efficiency of sourcing hydrogen from these media affects its economic feasibility. Electrolysis is a common approach used to convert the organic chemicals to hydrogen and CO2. Yet, the catalysts used for the electrolyzers can experience performance degradation due to impurities in the feedstock.
As a solution, the UCF technology (GDL design, electrolyzer assembly, and electrolysis method) permits smaller molecules, such as methanol, to pass through while excluding larger organic contaminants from reaching the catalyst surface, which are more detrimental to catalytic performance. In the electrolyzers, the GDL is set between the proton exchange membrane and the graphite plates.
Technical Details: Made of polymeric or crystalline materials, the UCF screening GDL lets its pore size determine the size and type of molecules that can pass through. By replacing non-crystalline carbon materials with ones formed of a thin crystalline material such as zeolite, polymeric membrane, or metal-organic frameworks (MOFs), the invention selectively allows small molecules to traverse through the gas diffusion layer. The design excludes larger molecules by tuning the aperture, solubility/ diffusivity, and pore sizes of these microporous materials. Thus, the GDL minimizes the energy penalty caused by larger organic impurities, i.e., raised cell potential needed to generate hydrogen at a fixed rate. This maintains the cell potential below the threshold where catalysts are oxidized while still preserving industrially relevant current densities (>200 mA cm-2).
In one embodiment of the invention, a selective gas diffusion layer protects the catalyst from being poisoned by the organic impurities in crude liquid organic hydrogen carrier (LOHC) feedstocks while allowing methanol or similarly small LOHC molecules to cross, reducing the cost of distillation of crude feedstock or the cost of frequent catalyst replacement.
Partnering Opportunity: The research team is seeking partners for licensing, research collaboration, or both.
Benefit
Significantly lowers purification steps for upgrading crude feedstock to grade feedstockMinimizes energy needed to convert organic feedstock to hydrogen at the point of useCan reduce the electricity consumption of the electrolyzer by about 50 percent, compared to water electrolysis per kg H2 producedMarket Application
Companies that focus on methanol electrolysis or methanol fuel-cellsSmall-scale hydrogen generation at locations where electricity cost is highChemical purification in catalyst-driven processes where larger organic species are present and can poison the catalyst
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