The Rational Design of a Single‐Component Photocatalyst for Gas‐Phase CO<sub>2</sub> Reduction Using Both UV and Visible Light

Hoch, Laura; Wood, Thomas E.; O’Brien, Paul G.; Liao, Kristine; Reyes, Laura M.; Mims, Charles A.; Ozin, Geoffrey A.

doi:10.1002/advs.201400013

Cited by 195 publications

(179 citation statements)

References 49 publications

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“…S3), this trend in photocatalytic activity remains. We attribute this effect to a decrease in the number of active defect sites, specifically surface hydroxides and oxygen vacancies, within the material (18). In a separate study, which combined theoretical simulations and kinetics experiments, we have confirmed that both hydroxides and oxygen vacancies are needed at the active site to facilitate the reduction of CO 2 to CO (17).…”

Section: Resultssupporting

confidence: 49%

“…4B). Our previous work with these materials has shown that CO 2 binds weakly to the surface of defected indium oxide, generally as carbonate, bicarbonate, and formate species (17,18). These weakly adsorbed species could impact the relaxation dynamics by altering the energetics of the surface.…”

Section: Resultsmentioning

confidence: 99%

“…Previously, our group has demonstrated that highly defected nanostructured In 2 O 3-x (OH) y functions as an effective gas-phase photocatalyst for the reduction of CO 2 to CO via the reverse water-gas shift reaction (RWGS) (17)(18)(19)(20). Notably, the photocatalytic activity was found to be strongly correlated to the number and the type of defects present in the material.…”

mentioning

confidence: 99%

“…It has a relatively high conduction band, and common defects such as oxygen vacancies (O v ) have been shown to cause electron accumulation on its surfaces (15), both of which could aid in facilitating electron transfer to adsorbed molecules such as CO 2 . Additionally, indium oxide is also very stable under illumination, unlike other similarly promising semiconductors such as metal sulfides, which can degrade under illumination, particularly in the presence of water (6, 16).Previously, our group has demonstrated that highly defected nanostructured In 2 O 3-x (OH) y functions as an effective gas-phase photocatalyst for the reduction of CO 2 to CO via the reverse water-gas shift reaction (RWGS) (17)(18)(19)(20). Notably, the photocatalytic activity was found to be strongly correlated to the number and the type of defects present in the material.…”

mentioning

confidence: 99%

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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.

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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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Section: Resultssupporting

confidence: 49%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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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.

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“…7,17,18 Though the In 2 O 3 NPs still retain significant oxide character, they gained hydroxide moieties, likely through hydration from ambient water vapor. Peaks corresponding to oxygen vacancies, as seen in other, similar systems, 19,20 were not observed in any of these spectra.…”

Section: Resultsmentioning

confidence: 72%

Enhanced Carbon Dioxide Reduction Activity on Indium-Based Nanoparticles

White

Bocarsly

2016

J. Electrochem. Soc.

102

105

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Nanoparticles of indium, indium hydroxide, and indium oxide were synthesized and evaluated for their electrocatalytic abilities in the reduction of CO 2 to formate. These nanoparticles were characterized with several microscopic and spectroscopic techniques in order to investigate their structure and surface features. Their electrochemical behavior was also probed through voltammetry and bulk electrolysis. faradaic efficiencies approaching 100% were achieved on these particles at potentials as positive as −1.3 V vs. Ag/AgCl, which represents a significant decrease in the overpotential compared to that observed using bulk indium electrodes. The nanostructuring of the particles and the partial surface oxidation of the indium nanoparticles to yield catalytic surface indium hydroxide species are implicated in the high efficiencies at low overpotentials. Recent decades have seen the rapid rise in the amounts of carbon dioxide, a greenhouse gas, present in both the atmosphere and the oceans, as well as a concomitant increase in global temperatures. 1This heating trend is predicted to amplify if net CO 2 emissions from fossil fuels continue to grow unabated, leading to a mean surface temperature increase of up to 4• C by 2100. 2 Therefore, a move away from fossil fuels toward renewable sources of energy such as wind and solar is essential for the long-term maintenance of the environment.The reduction of carbon dioxide to fuels and chemicals is an important component of a future energy portfolio based on renewable sources that seeks to mitigate carbon levels. The formation of useful chemicals from CO 2 rather than petroleum decreases the net CO 2 emissions and reduces reliance on oil. Generating high energy density carbon-based fuels, though only carbon-neutral and not carbonnegative, aids in load-leveling with intermittent power sources, leading to the production of fuels during periods of high output and the consumption during periods of low output.The electrochemical reduction of CO 2 on metal electrodes in aqueous solution has been studied for decades.3 Heavy post-transition metals, including indium, tin, lead, and bismuth yield predominantly formate, with small amounts of CO and H 2 as well. These metals have high overpotentials for water reduction, which allows them to be more selective for CO 2 reduction than most transition metals. However, the CO 2 reduction overpotentials are also fairly large, typically on the order of 1 V, significantly decreasing the energy efficiency of conversion. These metals have been proposed to reduce CO 2 in a oneelectron rate-determining step to the weakly adsorbed or free CO 2•− radical anion, which can then be protonated and reduced by another electron to yield formate.3 However, the formal redox potential for this process is −1.85 V vs. SHE, 4 considerably more negative than the potentials at which products are formed.Recent, more in-depth investigations on the mechanism of formate production on these metals have led to a greater understanding of the role of surface species in th...

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Frustrated Lewis Pairs Accelerating CO₂ Reduction on Oxyhydroxide Photocatalysts with Surface Lattice Hydroxyls as a Solid‐State Proton Donor

Wang

Lü

Wang

et al. 2018

Adv Funct Materials

116

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Light-driven CO 2 reduction into high value-added product is a potential route to convert and store solar energy. Here, using the hydroxyls on an oxyhydroxide photocatalyst, CoGeO 2 (OH) 2 , as solid-state proton source to reduce the CO 2 into CH 4 is proposed. It is found that under irradiation, the lattice hydroxyls on surface of CoGeO 2 (OH) 2 are oxidized by photogenerated holes, resulting in the generation of oxygen vacancies (O Vs ) and protons. The photoinduced O Vs (Lewis acid) and its proximal surface hydroxyls (Lewis base) are more likely to form the frustrated Lewis acid-base pairs, which can capture, activate, and reduce CO 2 with the assistance of protons into CH 4 . The surface lattice hydroxyls are able to regenerate when the catalyst is exposed to the water molecule-containing atmosphere, thus achieving a sustainable CO 2 conversion. The proposed CO 2 reduction by self-breathing surface hydroxyls may open a new avenue to use photocatalysis for energy conversion.

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The Rational Design of a Single‐Component Photocatalyst for Gas‐Phase CO₂ Reduction Using Both UV and Visible Light

Cited by 195 publications

References 49 publications

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

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

Enhanced Carbon Dioxide Reduction Activity on Indium-Based Nanoparticles

Frustrated Lewis Pairs Accelerating CO₂ Reduction on Oxyhydroxide Photocatalysts with Surface Lattice Hydroxyls as a Solid‐State Proton Donor

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The Rational Design of a Single‐Component Photocatalyst for Gas‐Phase CO2 Reduction Using Both UV and Visible Light

Cited by 195 publications

References 49 publications

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

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

Enhanced Carbon Dioxide Reduction Activity on Indium-Based Nanoparticles

Frustrated Lewis Pairs Accelerating CO2 Reduction on Oxyhydroxide Photocatalysts with Surface Lattice Hydroxyls as a Solid‐State Proton Donor

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The Rational Design of a Single‐Component Photocatalyst for Gas‐Phase CO₂ Reduction Using Both UV and Visible Light

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

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

Frustrated Lewis Pairs Accelerating CO₂ Reduction on Oxyhydroxide Photocatalysts with Surface Lattice Hydroxyls as a Solid‐State Proton Donor