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Oxygen Production and Delivery on Demand

Description:

TECHNOLOGY AREA(S): Bio Medical 

OBJECTIVE: To develop an efficient technology for medical grade oxygen generation with water as the feedstock and to provide a potential solution (deliverable prototype hardware) for the Armys medical oxygen requirement (or other DoD requirement). 

DESCRIPTION: Oxygen is a necessary substance for human beings and has been widely used for the patient in the battlefield; it is a life-saving capability regulated as a drug by the FDA. In terms of the medical-level oxygen, high purity without any contamination is essentially required. On another hand, the safety and the transportation size have to be considered for the military purpose. For example, the conventional high pressure gas cylinders have safety related issues and concerns. At the present time, oxygen is often produced using pressure swing absorption (PSA) or vacuum swing adsorption (VSA) techniques. The limitations of these techniques include the large foot print, heavy weight, and high power consumption. Moreover, since air is used as the feedstock, the oxygen purity has often remained a concern, particularly on a battlefield. As a result, further purification is often required. Alternatively, high-purity oxygen can be obtained through the electrolysis of water, which can produce ultrapure oxygen at low pressure. One limitation of this technique is the use of deionized water in conventional electrolyzers and the requirement of significant electrical power. Recent advances in photoelectrochemical (PEC) water splitting has shown that it is possible to produce large quantities of oxygen directly from water and sunlight. In general, the reaction of water-splitting includes two half reactions: the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), which can be driven by solar energy and/or electrical energy.1-4 In this process, high purity hydrogen is also separately generated and can be used as fuels in the battlefield. Various materials and approaches have been developed for PEC water splitting. The scope of this project is to identify the suitable photoelectrode materials for long-term stable oxygen generation from water and to demonstrate a compact prototype unit that is able to deliver high purity oxygen with a flow rate of 10 to 20 liters per minute. The system weight, power consumption, and maintenance requirements need to compare favorably to the conventional VSA or PSA technologies. Moreover, the water requirement should be no higher purity than typical bottled drinking water. Considering the specificity and complexity of military situation, the long-term stable operation needs to be evaluated and compared to alternative technologies. 

PHASE I: To demonstrate oxygen generation with water as the feedstock, and to determine the technical feasibility for achieving a flow rate of 10-20 liter per minute. Detailed analysis of the predicted performance needs to be developed. The water requirement needs to be identified with goal of using purified water (without distilling or deionizing) as a source, and the effect of water on the efficiency of oxygen generation and the purity level of oxygen needs to be thoroughly evaluated. For patient use, the oxygen produced would need to meet US Pharmacopeia standards for medical oxygen. 

PHASE II: To develop, test, and demonstrate a prototype to produce medical grade oxygen with typical drinking water as the feedstock, and to further define field test objectives and perform limited testing of the system efficiency and stability. The minimum oxygen generation rate should be in the range of 10 to 20 liter per minute, and the system size, weight, and power consumption should be compared favorably with the conventional VSA and PSA equipment. Compliance with FDA medical regulations would also need to be pursued once the standards on the water quality are developed. Oxygen quality monitoring procedures would be developed in accordance with regulatory authorities. 

PHASE III: Continued research and development toward high efficiency (expected up to 20% within 5 years) and reliability. Manufacturable process and epitaxial growth considerations for oxygen generating materials should be made and pursued, beyond prototype stages of development. Life testing and generation rate capabilities should be assessed for production systems, including potential for system scale-up to as much as 120 liters per minute to meet the requirements of a deployed intensive care unit. 

REFERENCES: 

1: Hisatomi, T.; Kubota, J.; Domen, K., Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting. Chem. Soc. Rev. 2014, 43 (22), 7520-7535.

2: Gratzel, M., Photoelectrochemical cells. Nature 2001, 414 (6861), 338-344.

3: Kibria, M. G.; Mi, Z., Artificial photosynthesis using metal/nonmetal-nitride semiconductors: current status, prospects, and challenges, J. Mater. Chem. A 2016, 4, 2801-2820.

4: Hu, S; Shaner, R. M.; Beardslee, J. A.; Lichterman, M.; Brunschwig, R. S.; Lewis, N. S., Amorphous TiO2 coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation, Science, 2014, 344 (6187), 1005-1009.

 

KEYWORDS: Oxygen, Water Splitting, Photoelectrochemical, Water Oxidation, Photoelectrode, Semiconductor 

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