Energy and Climate Impacts of Producing Synthetic Hydrocarbon Fuels from CO<sub>2</sub>

Giesen, Coen van der; Kleijn, René; Kramer, Gert Jan

doi:10.1021/es500191g

Cited by 137 publications

(123 citation statements)

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“…ΔG°∼ 665 n kJ=mol ðARCÞ [4] combustion and, as generally proposed, would be carried out as separate unit operations, each with its attendant efficiency losses and capital and operating costs (19,20). We report here a photothermochemical process for driving the alkane reverse combustion (ARC) reaction (reaction 4) to produce C 1 to C 13 hydrocarbons in a single operation unit.…”

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confidence: 99%

RETRACTED: Solar photothermochemical alkane reverse combustion

Chanmanee

Islam

Dennis

et al. 2016

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

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A one-step, gas-phase photothermocatalytic process for the synthesis of hydrocarbons, including liquid alkanes, aromatics, and oxygenates, with carbon numbers (Cn) up to C13, from CO2 and water is demonstrated in a flow photoreactor operating at elevated temperatures (180–200 °C) and pressures (1–6 bar) using a 5% cobalt on TiO2 catalyst and under UV irradiation. A parametric study of temperature, pressure, and partial pressure ratio revealed that temperatures in excess of 160 °C are needed to obtain the higher Cn products in quantity and that the product distribution shifts toward higher Cn products with increasing pressure. In the best run so far, over 13% by mass of the products were C5+ hydrocarbons and some of these, i.e., octane, are drop-in replacements for existing liquid hydrocarbons fuels. Dioxygen was detected in yields ranging between 64% and 150%. In principle, this tandem photochemical–thermochemical process, fitted with a photocatalyst better matched to the solar spectrum, could provide a cheap and direct method to produce liquid hydrocarbons from CO2 and water via a solar process which uses concentrated sunlight for both photochemical excitation to generate high-energy intermediates and heat to drive important thermochemical carbon-chain-forming reactions.

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confidence: 99%

RETRACTED: Solar photothermochemical alkane reverse combustion

Chanmanee

Islam

Dennis

et al. 2016

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

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“…An important challenge associated with using renewable energy sources, such as solar, is their inherent intermittent nature (4)(5)(6). The emerging field of solar fuels seeks to address this issue by storing radiant solar energy in chemical bonds, which can then be released on demand and act as a drop-in replacement for traditional fossil fuels (7)(8)(9)(10)(11). By using the greenhouse gas, CO 2 , currently regarded as a waste product, as a feedstock and converting it into valuable products such as solar fuels or platform chemicals, we could simultaneously address concerns over climate change and energy security while creating significant economic benefits (12)(13)(14).…”

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confidence: 99%

Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO ₂ reduction

Hoch

Szymanski

Ghuman

et al. 2016

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

101

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In 2 O 3-x (OH) y nanoparticles have been shown to function as an effective gas-phase photocatalyst for the reduction of CO 2 to CO via the reverse water-gas shift reaction. Their photocatalytic activity is strongly correlated to the number of oxygen vacancy and hydroxide defects present in the system. To better understand how such defects interact with photogenerated electrons and holes in these materials, we have studied the relaxation dynamics of In 2 O 3-x (OH) y nanoparticles with varying concentration of defects using two different excitation energies corresponding to above-band-gap (318-nm) and near-band-gap (405-nm) excitations. Our results demonstrate that defects play a significant role in the excited-state, charge relaxation pathways. Higher defect concentrations result in longer excited-state lifetimes, which are attributed to improved charge separation. This correlates well with the observed trends in the photocatalytic activity. These results are further supported by density-functional theory calculations, which confirm the positions of oxygen vacancy and hydroxide defect states within the optical band gap of indium oxide. This enhanced understanding of the role these defects play in determining the optoelectronic properties and charge carrier dynamics can provide valuable insight toward the rational development of more efficient photocatalytic materials for CO 2 reduction.indium oxide | solar fuels | CO 2 hydrogenation | transient absorption | surface defects C oncerns over climate change and the projected rise in global energy demand have motivated researchers to develop alternative, more sustainable ways to generate energy from naturally abundant and renewable sources (1-3). An important challenge associated with using renewable energy sources, such as solar, is their inherent intermittent nature (4-6). The emerging field of solar fuels seeks to address this issue by storing radiant solar energy in chemical bonds, which can then be released on demand and act as a drop-in replacement for traditional fossil fuels (7-11). By using the greenhouse gas, CO 2 , currently regarded as a waste product, as a feedstock and converting it into valuable products such as solar fuels or platform chemicals, we could simultaneously address concerns over climate change and energy security while creating significant economic benefits (12)(13)(14). However, despite recent advances in the development of active materials that can drive the photocatalytic reduction of CO 2 into useful chemical species, much remains unknown about the fundamental physical properties that control the activity of a photocatalyst. To facilitate the rational development and improvement of photocatalytic materials, a detailed understanding of the complex interplay between chemical, optical, and electronic processes is needed.Indium oxide has many favorable optical, electronic, and surface properties that make it a compelling choice as a photocatalyst for CO 2 reduction. It has a relatively high conduction band, and common defects such as oxyge...

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“…From a climate perspective, it might be preferable to capture and store CO2 underground, using CCS technology, and not convert CO2 into a fuel that after combustion will be released to the atmosphere again (van der Giesen et al, 2014;Sternberg and Bardow, 2015). If the CO2 has been captured from burning fossil fuels, CCS will avoid increased CO2 concentration, and if the CO2 is captured from burning biomass (or from air), CCS will decrease the atmospheric CO2 concentration, ceteris paribus.…”

Section: Discussionmentioning

confidence: 99%