Photoelectrochemical Cells from Earth Abundant Materials Sheryl H. Ehrman , University of Maryland College Park, DM

1. Photoelectrochemical Cells from Earth Abundant MaterialsSheryl H. Ehrman, University of Maryland College Park, DMR 0806610 Outcome: Researchers at University of Maryland have created a semiconductor film from the earth abundant elements copper and lithium – with improved conductivity and > 1% solar to hydrogen conversion efficiency. Impact: These films absorb solar energy and use the energy to split water and generate hydrogen, a clean renewable energy. Explanation:A scalable method for hydrogen generation by splitting water via a PEC cell was studied. Copper oxide (CuO) and Li doped CuO semiconductor nanoparticles made by flame spray pyrolysis were spin coated on conducting indium tin oxide substrates and served as photocathodes for photoelectrochemical splitting of water. Professor Sheryl Ehrman (left), of the Department of Chemical and Biomolecular Engineering at the University of Maryland led the team of undergraduate, graduate and high school students. Students shown here: KosiAroh, middleand Chia Ying Chiang, right. Courtesy of Faye Levine A PEC cell based on CuO nano-photocatalysts. (courtesy of Chia-Ying Chiang)

2. Addition of Lithium Improves Performance Sheryl H. Ehrman, University of Maryland College Park, DMR 0806610 Addition of lithium is known to improve conductivity of copper oxide, and here, it is shown that Li improves photoelectrochemical performance. Samples with Li dopant have better photocurrent density compared to undoped CuO. The photocurrent density increased by ~ a factor of 5 over the undoped sample at an applied voltage of -0.55 V vs. Ag/AgCl, when 2 at% Li dopant was added. However, when the Li concentration was further increased, photocurrent density decreased. Li+ is comparable in size to Cu2+ but the difference in valency may lead to defects that serve as recombination centers for the photon generated electron and hole pairs and thus decrease the photocurrent density. Dopant concentration effects on CuO film: film with thickness of 850 nm and sintered at 450 oC for 1 hr. (courtesy of S. Ehrman)

3. Middle School Students Discussing Energy on a Global ScaleSheryl H. Ehrman, University of Maryland College Park, DMR 0806610 The integrated education and outreach effort of this project includes the development of activities for a middle school summer camp focused on nanoscience. Summer camp participants discuss energy usage in the US and in India, and discuss how energy will be used in both countries in the future with collaborators and students at Dayalbagh Educational Institute in Agra, India. Students then visit the labs of Professors Adomaitis, Zachariah and Ehrman at the University of Maryland to learn about the development of technologies for solar water splitting. Professor Ehrman with middle school UMD MRSEC Nanoscience summer camp participants, in her lab (left) and on a videoconference (right) with research collaborators and students at Dayalbagh Educational Institute in Agra, India in July 2011. Courtesy D. Hammer.