My research is focused in five areas, 1) environmental interfaces, specifically atmospheric reactions that occur on mineral dust surfaces with trace pollutant gases and the development of materials for efficient nutrient recovery from wastewater streams, 2) the conversion of natural gas to alternate fuels via gas phase photochemistry, 3) development of laboratory experiments for mass distribution either as an outreach project or high school/undergraduate laboratory experiment, 4) using a combinatorial approach to identify semiconducting materials that can efficiently split water into hydrogen and oxygen using sunlight or reduce carbon dioxide into a useable fuel sources, and 5) developing learning progressions for students from middle school to introductory collegiate courses that are centered around quantitative reasoning in ecology and environmental literacy.
I. Environmental Interfaces
Aerosol Atmospheric Reactions
Our interest in environmental chemistry occurs at both atmospheric interfaces (e.g. clay mineral reacted with methane, SO2, and CO2) as well as solid/solution interfaces that occur in the environment. A lack of understanding exists on the role these interfaces in the environment, especially under irradiation. A reaction chamber has been built to investigate the solid/gas and the solid/liquid/gas interfaces under irradiation.
Our laboratory uses a number of instruments such as Attenuated Total Reflectance (ATR)-Fourier transform infrared spectroscopy (FTIR) and Gas Chromatograph-Mass Spectrometry (GC/MS) as well as UV-VIS Spectroscopy, X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) to characterize natural and synthetic samples. By better understanding the properties and reactions that occur that these interfaces and the products that are produced, we can better inform atmospheric modelers to improved understanding of climate change
Materials for Efficient Nutrient Recovery from Wastewater Streams
In collaboration with Dr. Jonas Baltrusaitis from Lehigh University, we have been working on one of the key forthcoming global challenges which will be maintaining a clean, useable natural water supply. Anthropogenic wastewater is an unavoidable result of population growth and societal development; therefore the treatment of wastewater is of the utmost importance. The mineral struvite (magnesium ammonium phosphate hexahydrate, MgNH4PO4·6H2O) is a crystalline material that occurs naturally in decomposing organic materials and been observed in sludge derived from the anaerobic digestion of animal farming liquid wastes and treated wastewater sludge. The accumulation of struvite on pipe walls and equipment surfaces has plagued the wastewater treatment industry though the formation of struvite prior to the treatment process could potentially provide a pathway for the sustainable recovery of the major nutrients nitrogen (N) and phosphorus (P). Current methods of nutrient removal from wastewater are mostly based on insoluble Fe, Al and Ca salt formation followed by landfill disposal without returning them to the environment. Struvite is one of the most promising chemical platforms for recovering nutrients, which previously was done using expensive water-soluble magnesium salts. Recently our objectives were to examine the potential of low solubility, naturally abundant magnesium inorganic materials (MgO and MgCO3) for the utilization of nutrient recovery from wastewater via time resolved ex situ XRD, ATR-FTIR and Raman analyses, and SEM measurements. We have synthesized and characterized struvite made from the reaction of dibasic ammonium phosphate ((NH4)2HPO4) and different magnesium precursors (MgO, MgCO3, and MgCl2) at various concentrations and time points. Our manuscript to ACS Sustainable Chemistry & Engineering (http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.6b02327), which was recently accepted. We are continuing to monitor these reactions under more complex, realistic systems.
II. Natural Gas Conversion
In another collaboration with Dr. Jonas Baltrusaitis, we are to studying the conversion of natural gas to halogenated products under mild condition. Natural gas is envisioned as the primary source of hydrocarbons in the foreseeable future. With the high cost of transporting natural gas in its gaseous form, methodologies are being investigated to perform catalytic CH4 conversion using direct sunlight to a liquid that can be easily and inexpensively transported from remote natural gas extraction sites (i.e. shale gas sites). We are currently in the process of trying to determine if there is an affordable, straightforward method by which natural gas can be electro- or photo(electro)catalytically be converted to a more transportable fuel. This could lead to a new route for C-H bond activation and potentially impact the natural gas industry as a whole. Gas Chromatography/Mass Spectrometry (GC-MS) was used to analyze the products produced in a reaction chamber. We have investigated a variety of pH solutions for both chlorine and bromine salts.
III. Development of Laboratory Experiments
I am currently the International Coordinator for the Solar Army and co-PI of Outreach for the National Science Foundation (NSF) funded Center for Chemical Innovation (CCI) Solar Fuels (http://www.ccisolar.caltech.edu/). The mission of CCI Solar Fuels is to target the critical science underpinning the solar-driven decomposition of water into hydrogen and oxygen, with the focus being the efficient and economical conversion of solar energy into stored chemical fuel. The current outreach effort coined “The Solar Army” (http://thesolararmy.org/) consists of the following projects: Solar Energy Activity Lab (SEAL), Juice from Juice (JfJ) and Heterogeneous Anodes Rapidly Perused for Oxygen Overpotential Neutralization (HARPOON).
The SEAL kit, developed by Gates and Jay Winkler at Caltech, is described in the Journal of Chemical Education (http://pubs.acs.org/doi/abs/10.1021/ed300574x). The JCE manuscript was selected by the American Chemical Society for the National Chemistry Week 2013 celebration with the theme of "Energy! Now and Forever” in September 2013 (http://pubs.acs.org/page/jceda8/ncw2013.html). The HARPOON kit, developed in collaboration with Professor Shannon Stahl's lab at UW Madison (funded by the Henry & Camille Dreyfus Foundation and the National Science Foundation) is also described in the Journal of Chemical Education (http://pubs.acs.org/doi/abs/10.1021/acs.jchemed.5b0059).
Most recently, were highlighted in the news magazine of the International Union of Pure and Applied Chemistry (IUPAC) Chemistry International, Vol. 38, Issue 6, November-December 2016 (https://www.degruyter.com/view/j/ci.2016.38.issue-6/issue-files/ci.2016.38.issue-6.xml).
IV. Combinatorial Search for Semiconductors
Catalysts for Solar Water Splitting
This area of research is a known as a “materials problem”. We are performing combinatorial searches for potential mixed-metal oxides (likely semiconducting materials) that are inexpensive, stable, light-absorbing and earth-abundant materials that can be used to split water into its elemental components hydrogen (H2) and oxygen (O2) using only sunlight (NSF-funded). Alternatively, these potential catalysts could also be used to efficiently and inexpensively reduce carbon dioxide (CO2) into useable fuels if the material is deemed to have the proper band alignments and catalytic activity.
Students in my lab are working to discover and optimize materials that have been identified as potential “hits” or highly performing combination. This research area has stemmed out of my research on developing educational outreach projects. With the mission of the CCI Solar Fuels being to target the critical science underpinning the solar-driven decomposition of water into hydrogen and oxygen, discovery of materials to split water are of the utmost importance. Currently few materials will accomplish this process and none will do it inexpensively or efficiently.
The most promising results are the addition of cobalt or molybdenum to a ternary combination consisting of Aluminum:Nickel:Iron (4:4:2 or 1:8:9 ratios) to create an active quaternary combination. Potentially active materials are characterized using a variety of technique including X-ray Fluorescence Spectroscopy (XRF), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) at UWO.
We continue to examine unique combinations on HARPOON. Recently, we have begun to investigate combinations discovered as “hits” on HARPOON versus “hits” discovered on SHArK/SEAL. HARPOON results indicate oxygen has evolved whereas SEAL/SHArK show photocurrent produced by the catalyst which could signal a possible material for oxygen evolution. We are investigating whether or not photocurrent is a reliable method for searching for catalysts for oxygen evolution.
V. Quantitative Reasoning in the Sciences and the Development of Learning Progressions
This is a collaborative project that was a NSF-funded Mathematics and Science Partnership project entitled The Culturally Relevant Ecology, Learning Progressions and Environmental Literacy that aimed to establishing learning progressions for environmental science. Studying the trajectory of learning that leads to the development of environmentally literate citizens capable of making informed decisions has not been widely investigated in terms of the quantitative reasoning that one must use to “be informed”. This project was a collaboration of six universities; four Long Term Ecological Research (LTER) Sites and LTER partner school districts that ended in 2013. Research teams were established at partner universities (UW Oshkosh is included here) to lead efforts on study of three strands (i.e., carbon, water, and biodiversity) and three themes (i.e., quantitative reasoning, citizenship, and cultural relevance) within environmental literacy.
The Quantitative Reasoning team, Drs. Robert Mayes and Kent Rittschof (Georgia Southern University), Jennifer Harris Forrester (University of Wyoming), and Franzi Peterson (University of Maine), developed a learning progression on quantitative reasoning by creating and collecting assessment data on students around the country in the areas of biodiversity, water and carbon. Thus far, we have been able to identify four areas of development for students: the Act of Quantification, Quantitative Literacy, Quantitative Interpretation, and Quantitative Modeling.
QR is of special interest due to the ever increasing need for problem solving citizenship. While scientists have been investigating human impact on the environment for centuries, the need for quantitatively literate citizens who can make informed decisions about environmental issues has become imperative for those outside of the scientific community to understand how human impact within the local, regional, and global environments alter and shape environmental issues.
This work has resulted in the following peer-reviewed journal publications: (Numeracy (http://scholarcommons.usf.edu/numeracy/vol7/iss2/art5/ and http://scholarcommons.usf.edu/numeracy/vol8/iss2/art4/) and the International Journal of Science Education (http://www.tandfonline.com/doi/full/10.1080/09500693.2013.819534), and a peer-reviewed article in the WISDOMe Monograph: Quantitative Reasoning and Mathematical Modeling: A Driver for STEM Integrated Education and Teaching in Context.