Weapons of Mass Construction in the War on Climate Change: Heterogeneous Catalysis and Electro-Catalysis

Geoff’s latest opinion editorial published in Advanced Science News argues the case for using electro-catalysis and heterogeneous catalysis to transform CO2 into fuels.

The full article can be read on the Advanced Science News website.

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A Burning Question: Anthropogenic Methane!

CO2 is generally thought of as the primary contributor to climate change. Recently, however, the significance of CH4 as a greenhouse gas has been growing due to the emissions from shale-gas wells. Geoff’s latest opinion editorial published in Advanced Science News details what we can do about the rapidly increasing concentrations of CH4 and CO2 in our atmosphere.

The full article can be read on the Advanced Science News website.

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Geoff Wins the 2016 World Technology Award in Energy!

Congratulations to Geoff for winning the WTN award in the energy category!

Read more about it on the UofT News website.

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Solar Powered Reverse Water Gas Shift Reaction, CO2 + H2 + hv -> CO + H2O

In this work, published in the November 2016 issue of the Proceedings of the National Academy of Sciences, we investigate the role of oxygen vacancy and hydroxide defects on the electronic and photocatalytic properties of In2O3-x(OH)y nanocrystals that have been shown to effectively reduce CO2 to CO via the solar powered reverse water–gas shift reaction CO2 + H2+ hv CO + H2O.

To understand how such defects, affect photogenerated electrons and holes in these nanomaterials, we used transient absorption spectroscopy to study the relaxation dynamics of these nanocrystalscontaining varying concentration of oxygen vacancy and hydroxide defects.

This analysis showed that higher defect concentrations result in longer excited-state lifetimes, which are attributed to improved charge separation and correlate well with the observed trends in the photocatalytic activity.These results are further supported by density-functional theory calculations, which confirm the positions ofoxygen 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 CO2 reduction.

The full article can be viewed on the PNAS website with a subscription.

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CO2 Innovation: CO2 Chemistry and Engineering Solutions to Climate Change

Professor Ozin has written numerous opinion editorials for Materials Views about hot button issues in nanochemistry. The 55 opinion editorials published so far have been organized by Geoff into a compendium of essays focusing on CO2.

The full compendium of opinion editorials can be viewed here and here.

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Photo-desalination: There is more than One Way of Winning the Battle against Climate Change

In our Advanced Energy Materials 2016 paper, we have successfully synthesized ultra-black TiO2-x nanoparticles for water evaporation by coating and superhydrophobization of them on a stainless steel mesh. Increase of x in TiO2-x resulted in a darker material leading to more efficient solar energy to heat conversion and thus more efficient water evaporation. We believe that the high solar thermal conversion efficiency, low cost, low-toxicity, and good chemical stability make black TiO2-x nanoparticles a potentially useful material for converting solar energy to thermal energy for evaporation of seawater or brackish water in remote and rural areas where access to a centralized drinking water supply is unavailable.

The full article can be read on the Advanced Energy Materials website.

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Congratulations to Ab, Mo and Paul on the publication of their latest paper in ChemNanoCat entitled “photocatalytic properties of all four polymorphs of nanostructured iron oxyhydroxides”

In this work we report for the first time a comparative study of the physical, electronic and photocatalytic properties of all four polymorphs of nanostructured iron oxyhydroxides. In brief, we synthesized all four polymorphs of nanostructured iron oxyhydroxides, namely; goethite (α-FeOOH), akaganeite (β-FeOOH), lepidocrocite (ɣ-FeOOH), and feroxyhyte (δ-FeOOH) and fully characterized them by X-ray diffraction, electron microscopy, UV-Visible spectrophotometry, BET measurements and X-ray photoemission spectroscopy. The relationship between these iron oxyhydroxide polymorphs and their photocatalytic properties were explored by examining the extent of methylene blue (MB) degradation by each polymorph under visible light irradiation. Feroxyhyte exhibited the best photocatalytic properties and degraded 85% of the MB dye in five hours. In comparison, goethite, akaganeite and lepidocrocite degraded only 40%, 35% and 30% of the MB in five hours, respectively. In order to understand this trend, the surface area, particle size and shape, and electronic band properties were systematically studied and discussed. It was found that the rate of MB degradation relates mainly to the surface area of the FeOOH polymorphs more than any other factor. We are deeply indebted to Chenxi Qian for his graphical representation of the artscience encapsulated in our paper.

The full article can be read on the ChemNanoMat website.

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Some like it Hot: Carbon Dioxide Reduction: Visible and Near-Infrared Photothermal Catalyzed Hydrogenation of Gaseous CO2 over Nanostructured Pd@Nb2O5

Geoffry A. Ozin and co-workers demonstrate that the reverse water gas shift (RWGS) reaction, driven by a visible and near infrared responsive Pd@Nb2O5 is thermally activated with measured conversion rates as high as 1.8 mmol gcat−1 h−1, Advanced Science, 2016, DOI: 10.1002/advs.201670051. Specifically, the RWGS reaction is enabled by heat generated from thermalization of photoexcited charge carriers in the Pd nanocrystals that function as “nanoheaters” for the entire Pd@Nb2O5 assembly, through non-radiative relaxation of inter-band and intra-band conduction electron transitions. Overall this study advances our understanding of the underlying mechanism of photothermally driven CO2 reduction. Cover illustration by Chenxi Qian.

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CO2 on the Brain

Geoff’s latest Materials Views details the cognitive effects CO2 has on humans, referring back to two public health studies done in 2012 and 2015. Reductions in decision-making performance is observed in CO2 levels as low as 1000 ppm which is often exceeded in poorly ventilated rooms. With rapidly accelerating CO2 levels in the atmosphere, the concern for CO2 on public health grows with it.

The full article can be read on the Materials Views website.

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Laura Reyes, Common Sense Chemist

Laura Reyes has been featured in a recent ACCN article for her involvement in green chemistry. Her role with the Green Chemistry Initiative (GCI) at UofT and her PhD project focused on investigating how CO2 and H2 interact with the surface of metal oxides are also presented.

The full article can be read on the ACCN website.

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