Refined materials provide booster shot for solar energy conversion

An interdisciplinary team of Engineering at Illinois researchers has set its sights on improving the materials that make solar energy conversion/photocatalysis possible. Together, they have developed a new form of high-performance solar photocatalyst based on the combination of the TiO₂ (titanium dioxide) and other "metallic" oxides that greatly enhance the visible light absorption and promote more efficient utilization of the solar spectrum for energy applications.

"This is a fundamentally new way of approaching these matters," explained Lane Martin, who is an assistant professor in the Department of Materials Science and Engineering at Illinois. "Our research group incorporates aspects of condensed matter physics, semiconductor device engineering, and photochemistry to make new performance possible. From these materials we can imagine carbon-neutral energy production of clean-burning fuels, waste water purification and remediation, and much more.

"As a follow-up to our prior work, we expanded our discovery of new strongly absorbing energy materials," Martin added. "The overall concept is that we have developed a new form of high-performance solar photocatalyst based on the combination of the TiO₂ and 'metallic' oxides." The group's paper "Enhanced photoelectrochemical activity in all-oxide heterojunction devices based on correlated 'metallic' oxides," appears in the journal, Advanced Materials (Volume 25, Issue 43, pages 6201-6206). The researchers also have a patent application pending for this work.

According to Martin the research paper addresses the most pressing limiting factor of these materials for applications -- their poor absorption of light.

"This paper covers several new variations where we integrate chemically compatible correlated 'metallic' oxides with the model n-type, wide band gap oxide semiconductor TiO₂ to produce high-performance photocatalytic heterojunctions. These composite structures operate on the principle of hot carrier injection from the 'metallic' oxide into the TiO₂. "

These effects are made possible by harnessing the diverse range of correlated electron physics of common metallic oxide materials including n-type LaNiO₃ (lanthanum nickelate), SrRuO₃ (strontium ruthenate), and SrVO₃ (strontium vanadate) and p-type La_0.5Sr_0.5CoO₃ (lanthanum strontium cobaltite) and La_0.7Sr_0.3MnO₃ (lanthanum strontium manganite). These materials have been extensively explored (individually) for their novel electronic transport, magnetic properties, and other exotic physical phenomena and are widely utilized as epitaxial bottom electrodes in ferroic heterostructures.

Martin noted that one of the new materials studied (La _0.5Sr_0.5CoO₃-based devices) demonstrated photocatalytic activities that are 27-, 6.2-, and 3-times larger than that for a single-layer TiO₂ film, nanopowder Degussa P25 samples, and the prior report of devices based on SrRuO₃, respectively.

This work is partially supported by the College of Engineering's Strategic Research Initiatives (SRI) program which invests in promising new and emerging areas of engineering research.

"This project reflects the kinds of research endeavors that the SRI program is designed to support," explained Jennifer Bernhard, the College's associate dean for research. "It addresses key challenges in energy and the environment that face our society. The momentum of this work is tremendous. It cuts across disciplines and it has tremendous impact potential. We're all excited to see where the team takes it from here."