Photoelectrochemical Hydrogen Production from Urea - TOPIC AREA: Electrochemical Power Production and Energy Storage
Abstract
The objective of the proposed research is to enable the photoconversion of urea to hydrogen gas in a photoelectrochemical reactor employing high surface area, mesoscopic semiconductor electrodes coupled with a urea electrocatalyst. Urea is the dominant component of human and animal urine and is generated at quantities tons/day globally. Sustainable approaches to the production of chemical fuels and clean water are both recognized as Grand Challenges by the National Academy of Engineers, which we aim to accomplish synergistically through the proposed waste-to-fuel process, and furthers the DoD mission toward sustainable energy harvesting and conversion. The proposed research for the first time represents a viable approach toward harnessing sunlight to convert a renewable waste stream into stored chemical fuel using visible light absorbing semiconductor nanocrystals. The research objective will be accomplished through a robust experimental design, and the research is expected to yield new insights into synergistic approaches for the direct conversion of sunlight to stored chemical energy. Visible light absorbing semiconductors undergo photocorrosion in aqueous environment unless a sacrificial donor is introduced to stabilize the semiconductor. This research is aimed at suppressing the photocorrosion surface reaction through two approaches: (1) use of urea as sacrificial electron donor and (2) incorporation of a thin dielectric barrier layer to block water-mediated surface corrosion. The solution-based techniques to fabricate mesoscopic photosensitized electrodes with well-designed dielectric blocking layer will create a practical route to block photocorrosion reactions while synergistically promoting improved spatial separation of charge carriers and thus lower rate of recombination. Hydrolysis of organometallic precursors will be employed to deposit the dielectric barrier while controlling the film thickness and quality through catalytic control of the reaction rate. A new optical spectroscopy method will be deployed to quantitatively probe the relationship between binary semiconductor surface chemistry and adsorption of the organometallic precursor to fabricate high-quality dielectric layers. Charge transfer kinetics are the predominant driver of charge separation in photosensitized electrodes, thus elucidating the charge carrier behavior enables the rational design of the semiconductor-barrier-catalyst interface for maximum efficiency. Femtosecond transient absorption spectroscopy will be used to probe interfacial charge transfer and recombination kinetics. Electrodes will be employed in a photoelectrochemical reactor to evaluate their effectiveness in the conversion of urea to hydrogen gas without deleterious photocorrosion effects. The proposed research will advance fundamental understanding of (1) solution-based deposition of nanoscopic dielectric layers in mesoscopic electrode architectures, (2) the role of charge carrier kinetics in the design of coupled semiconductor-electrocatalyst assemblies, and (3) the relationship between the transient charge carrier kinetics and the steady state photoelectrode response.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 04, 2018
- Source ID
- W911NF1610580
Entities
People
- James Radich
Organizations
- Army Contracting Command
- Auburn University
- United States Army