Nitrogen Reducing Solar Cells

Guth, T. D.; Palmer, Miles R.; Salehi, J. Mohammad

doi:10.1007/978-1-4612-6245-9_11

Cited by 17 publications

(14 citation statements)

References 12 publications

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“…This reaction was first discovered in the 1940s by an Indian soil scientist but drifted into obscurity, perhaps due to war and the rise of industrial ammonia production. The hypothesis was revisited in the late 1970s and early 1980s with the pioneering work of Schrauzer and Guth, who demonstrated the photocatalytic production of ammonia over a variety of sterile desert sands. ,− This work was followed by several independent groups who were able to achieve similar results with titania-based catalysts, particularly when doped with transition-metals such as iron. − However, other groups were unsuccessful in reproducing these results and pointed out the thermodynamic challenges with the proposed conversion of nitrogen and water (two very stable reactants) to ammonia and oxygen (two relatively reactive products). This led to a contentious debate in Angewandte, − but no consensus was reached regarding the source of the disagreement.…”

Section: Current Progressmentioning

confidence: 99%

Photon-Driven Nitrogen Fixation: Current Progress, Thermodynamic Considerations, and Future Outlook

2017

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Over the last century, the industrialization of agriculture and the consumption of fossil fuels have resulted in a significant imbalance and redistribution in nitrogen-containing resources. This has sparked an interest in developing more sustainable and resilient approaches for producing nitrogencontaining commodities such as fertilizers and fuels. One largely neglected but emerging approach is photocatalytic nitrogen fixation. There is significant evidence that this process occurs spontaneously in terrestrial settings, and it has been demonstrated in numerous engineered systems. Yet many questions still remain unanswered regarding the rates, mechanisms, and impacts of photocatalytically producing fixed nitrogen "out of thin air". This work reviews the fascinating history of the reaction and examines current progress toward understanding and improving photofixation of nitrogen. This is supplemented by a quantitative review of the thermodynamic considerations and limitations for various reaction mechanisms. Finally, future prospects and preliminary performance targets for photocatalytic nitrogen fixation are discussed.

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Section: Current Progressmentioning

confidence: 99%

Photon-Driven Nitrogen Fixation: Current Progress, Thermodynamic Considerations, and Future Outlook

2017

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“…The correctness of this hypothesis was first verified through studies with sand from a southern California desert in 1979 (4).…”

Section: Andmentioning

confidence: 95%

“…4): TiO2 C2H2 + H20 + hv C2H4 + 1/2 02. [4] Because the photoreduction of C2H2 is significantly inhibited by N2, it was assumed (3) that both substrates are reduced at the same binding sites.…”

Section: Andmentioning

confidence: 99%

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Nitrogen photoreduction on desert sands under sterile conditions

Schrauzer

Strampach

Hui

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

107

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Sands from various geographic locations reduce N2 from the air to NH3 and traces of N2H4 on exposure to sunlight. This N2 photofixation occurs under sterile conditions on the surface of finely dispersed titanium minerals such as rutile, utilizing reducing equivalents generated through the photolysis of chemisorbed H20. Abiological N2 photofixation is suggested to be part of the nitrogen cycle in arid and semiarid regions. It is estimated that about 10 x 106 tons of N2 is photoreduced on the total surface of the earth's deserts per year.The band-gap of TiO2 of 2.9-3.2 eV (290-335 kJ/mol) is larger than the energy required for water dissociation (1.23 eV), rendering TiO2 a good substratum for water splitting into H2 and 02 on irradiation with near-UV light, as was first shown by Fujishima and Honda (1,2 As outlined elsewhere (3), the reduction of N2 to NH3 and N2H4 appears to proceed in a stepwise fashion on 2-electron reducing sites at the TiO2 surface, via chemisQrbed N2H2 as the intermediate. In similar fashion, C2H2 is photoreduced to C2H4 (Eq. 4): TiO2 C2H2 + H20 + hv C2H4 + 1/2 02.[4] Because the photoreduction of C2H2 is significantly inhibited by N2, it was assumed (3) that both substrates are reduced at the same binding sites.The fact that N2 is photoreduced even in the presence of oxygen and on exposure of the Fe-doped TiO2 powders to normal sunlight (3) and the wide distribution of titanium on the earth's crust suggested that molecular N2 is fixed photochemically on sun-exposed titanium oxide containing sands or minerals without the aid of microorganisms, notably in arid or semiarid regions of the earth. The correctness of this hypothesis was first verified through studies with sand from a southern California desert in 1979 (4).In the present paper we report that results of more extensive studies with sand samples collected from locations given in Table 1.Several theories of abiological N2 fixation were formulated, and in part substantiated experimentally, more than 30 years (7), but his theories were almost universally rejected and usually are not mentioned in the contemporary literature. Because Dhar used sand from the Jumna River near Allahabad for N2 photofixation experiments in 1951 (6), we included a sample from this location in our studies. We found it to be rich in rutile and photocatalytically active under our experimental condi-tions. The sands were tested for photoreducing activity under sterile conditions on exposure to sunlight, using '5N2-enriched N2 as the substrate. Experiments were also performed with UV light as the light source with N2 as well as with C2H2 as the substrate.The sands were also tested for N2 photooxidation activity. Bickley and Vishwanathan (8) reported that H202-pretreated TiO2 powder promotes the photooxidation of N2 to a chemisorbed species yielding NO on thermolysis. The mechanism of this reaction is unknown. However, NH3 is known (9) to be photooxidized on TiO2 surfaces in the presence of 02 without requiring H202 pretreatment. Hence, under our experiment...

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“…A good example is the photochemical fixation of dinitrogen (into ammonia or nitrate), a notion still obscure to geoscientists despite “significant evidence that this process occurs spontaneously in terrestrial settings” . It has been suggested that 10 Tg of N year –1 can be photochemically fixed on the Earth’s deserts, which is comparable to what is fixed by lightning (2–20 Tg of N year –1 ), , and an appreciable amount relative to total biological fixation across land ecosystems, estimated at 100–290 Tg of N year –1 , 150 Tg of N year –1 , or 40–100 Tg of N year –1 . Photochemical fixation may be more consequential in places where biological fixation is low: an estimate for deserts of up to 20 kg of N ha –1 year –1 based on measurements with sands is similar to biological fixation estimated at 5–11 kg of N ha –1 year –1 .…”

mentioning

confidence: 99%

The Abiotic Nitrogen Cycle

Doane

2017

ACS Earth Space Chem.

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Natural environments on Earth are amenable to a diverse array of chemical reactions that can convert one form of nitrogen into another, often with the participation of additional substances such as minerals, dissolved metals, and organic compounds. These processes collectively define a natural chemical nitrogen cycle, analogous to the familiar biologically driven cycle but even more intricate with respect to the number of pathways by which nitrogen can be transformed and transported across land, air, and water. The fully assembled abiotic nitrogen cycle manifests a landscape rich in opportunities for investigation either with or without parallel attention to biological processes.

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Nitrogen Reducing Solar Cells

Cited by 17 publications

References 12 publications

Photon-Driven Nitrogen Fixation: Current Progress, Thermodynamic Considerations, and Future Outlook

Photon-Driven Nitrogen Fixation: Current Progress, Thermodynamic Considerations, and Future Outlook

Nitrogen photoreduction on desert sands under sterile conditions

The Abiotic Nitrogen Cycle

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