Tag: Shannon Boettcher

Non-Platinum Group Metal Anodic Catalysts in Anion-Exchange-Membrane Electrolysis

Presenter: Sarah Beaudoin − Chemistry

Faculty Mentor(s): Shannon Boettcher, Grace Lindquist

(In-Person) Poster Presentation 

Electrolysis, also known as water splitting, consists of two half-reactions occurring within an electrolytic cell that make possible the extraction of storable and non-pollutive hydrogen gas. Anionexchange-membrane water electrolyzers (AEMWEs) in principle operate without soluble electrolyte using earth-abundant catalysts and cell materials and thus lower the cost of green H2. However, the degradation methods of specific catalysts when used in the electrolyzer are still unclear. This study outlines the durability and activity of five commercially available non-PGM catalysts in an AEMWE system. In-situ and ex-situ characterization of each catalyst explores its electrochemical performance, conductivity, and interaction with the polymer membrane. Initial results indicate that electrical conductivity of the catalyst is a significant factor in its performance as a water oxidation catalyst in pure water. More specifically, Co3O4 catalyst nanoparticles show the greatest potential to compete with the current industry standard, IrOx, in both stability and activity. Further development of cobalt oxide catalysts, through synthesis and characterization, is required to achieve competitive durability in industrially relevant operating conditions for a pure water membrane-electrode assembly (MEA).

Characterization of InxGax-1P grown by Close-Space Vapor Transport

Presenter: Benjamin Bachman

Faculty Mentor: Shannon Boettcher, Annie Greenaway

Presentation Type: Poster 45

Primary Research Area: Science

Major: Chemistry

Funding Source: UROP Mini-grant, University of Oregon, $1000

Indium gallium phosphide (InxGa1-xP) has shown promise as a potential material for photoelectrochemical (PEC) hydrogen generation through water-splitting, as well as for use as a passivation layer for high-efficiency gallium arsenide (GaAs) solar cells. We seek a better understanding of the growth conditions and source material preparation optimal for depositing InGaP2 onto GaAs using close-space vapor transport (CSVT). CSVT is a promising method for depositing materials such as InGaP2, because it uses less toxic precursors and has the potential to be scaled up to an industrial level. Using CSVT to deposit InGaP2 onto GaAs could potentially reduce the cost of manufacturing GaAs devices as well as reduce the risks involved that are inherent in status quo growth techniques such as metal-organic chemical vapor deposition. To characterize the InGaP2 we will utilize x-ray diffraction, x-ray fluorescence, Hall effect, SEM, non-aqueous photoelectrochemistry, and Mott-Schottkey analysis. Further work will determine if these devices would be well suited for PEC water-splitting or solar energy generation.

Energetic Loss From the Use of Hole Scavengers to Measure Photoelectrochemical Cell Efficiency Limits

Presenter(s): Adrian Gordon − Chemistry

Faculty Mentor(s): Shannon Boettcher

Poster 38

Research Area: Natural/Physical Science

Funding: Vice President for Research and Innovation (VPRI) Undergraduate Fellowship

Photoelectrochemical cells, which split water into hydrogen, a clean fuel, and oxygen, have shown great potential for efficiently storing solar energy. In these cells, the oxygen evolution half reaction (OER) limits the efficiency of the entire solar water splitting process. Therefore, accurate OER efficiency measurements are critical in evaluating electrode catalyst materials. Currently efficiency is measured using solution species known as hole scavengers. These species are assumed to collect all photogenerated holes, and thus indicate the energy conversion efficiency of the system. However, this assumption does not hold true for an entire class of OER catalysts, including two promising catalysts, nickel and iron, because of their “conductivity switching” behavior. Hole scavengers introduce energetic losses in these electrodes.
To quantify these energetic losses, in situ electrical measurements were taken to isolate electronic properties of the catalyst from those of the semiconductor on model photoanodes. Dual Working Electrode technique was used to collect data on two model systems: silicon and hematite coated with impermeable and permeable catalysts, respectively. It was found that hole scavengers hold surface catalysts, such as Ni, in their reduced state, thus creating an extraction barrier for holes generated in the semiconductor, and lowering the efficiency of electrochemical cells.

Semiconductor-Electrocatalyst Interfaces on Photoanodes Designed for Photoelectrochemical Cells

Presenter(s): Adrian Gordon

Faculty Mentor(s): Shannon Boettcher

Oral Session 3 S

Solar water splitting using photoelectrochemical cells is a promising method for storing solar energy in the form of hydrogen bonds. Photoelectrochemical cells consist of two surfaces, the photocathode and photoanode, at which hydrogen and oxygen evolve from an electrolyte solution. Thin metal or metal-oxide electrocatalyst films are often deposited onto silicon based photoanodes in order to catalyze the oxygen evolution reaction and to protect the silicon from corrosion. Previous research has shown that thinner electrocatalyst films are correlated with more efficient photoanodes. However, the underlying physical processes driving this correlation remain unclear. This research uses an electrodeposition technique combined with cyclic voltammetry and atomic force microscopy to gain a deeper understanding of the semiconductor-electrocatalyst interface on photoanodes.

Ultrathin Iridium Oxide Catalyst on a Conductive Support for the Oxygen Evolution Reaction in Acid

Presenter(s): Nathan Stovall—Chemistry

Faculty Mentor(s): Shannon Boettcher, Raina Krivina S

ession 5: The Bonds that Make Us

Anthropogenic climate change has driven interest in the research and development of clean
energy alternatives . Great advancements in renewable energy production have been made, but its intermittent nature requires the development of a large-scale storage technology . Water electrolysis is a promising solution to the storage dilemma, via the state-of-the-art proton exchange membrane (PEM) electrolyzers that can convert renewable energy into hydrogen fuel . However, the acidic operating conditions of PEM cells results in slow kinetics of the oxygen evolution reaction (OER) . Iridium oxide is the only catalyst capable of withstanding these harsh conditions, but its low abundance and high costs limit large-scale implementation . My research focuses on designing a novel sub-monolayer-thick iridium oxide catalyst on an inexpensive conductive support that would allow to decrease iridium loading while maximizing activity . We have developed a novel synthetic method for adhering a cheap commercially available iridium precursor (IrCODCl dimer) to the surfaces of inexpensive acid-stable metal oxide nanoparticles . The mechanism of the assembly was investigated with UV-vis spectroscopy, X-ray photoelectron spectroscopy, and NMR . We discovered that the dimer attaches in a surface-limited manor allowing for precise control over the catalyst’s thickness . The determination of the mass loadings was accomplished via x-ray fluorescence and ex-situ inductively coupled plasma induced mass spectroscopy . Electrochemical measurements conducted in pH 1 have shown exceptionally high intrinsic activity at significantly reduced mass loadings . We are currently working on improving the catalyst’s stability which might in the future allow for industrial-scale implementation of water electrolysis as renewable energy storage .