Heme biomolecule as redox mediator and oxygen shuttle for efficient charging of lithium-oxygen batteries.

One of the greatest challenges with lithium-oxygen batteries involves identifying catalysts that facilitate the growth and evolution of cathode species on an oxygen electrode. Heterogeneous solid catalysts cannot adequately address the problematic overpotentials when the surfaces become passivated. However, there exists a class of biomolecules which have been designed by nature to guide complex solution-based oxygen chemistries. Here, we show that the heme molecule, a common porphyrin cofactor in blood, can function as a soluble redox catalyst and oxygen shuttle for efficient oxygen evolution in non-aqueous Li-O2 batteries. The heme's oxygen binding capability facilitates battery recharge by accepting and releasing dissociated oxygen species while benefiting charge transfer with the cathode. We reveal the chemical change of heme redox molecules where synergy exists with the electrolyte species. This study brings focus to the rational design of solution-based catalysts and suggests a sustainable cross-link between biomolecules and advanced energy storage.

High-energy and thermal-neutron imaging and modeling with an amorphous silicon flat-panel detector.

The Los Alamos Neutron Science Center (LANSCE) operates two spallation neutron sources dedicated to research in materials science, condensed-matter physics, and fundamental and applied nuclear physics. Prior to 1995, all thermal neutron radiography at Los Alamos was done on a beam port attached to the Omega West reactor, a small 8MW research reactor used primarily for radioisotope production and prompt and delayed neutron activation analysis. After the closure of this facility, two largely independent radiography development efforts were begun at LANSCE using moderated cold and thermal neutrons from the Target-1 source and high-energy neutrons from the Target-4 source. Investigations with cold and thermal neutrons employed a neutron converter and film, a scintillation screen and CCD camera system, and a new high-resolution amorphous silicon (a-Si) flat-panel detector system. Recent work with high-energy neutrons (En > 1 MeV) has involved storage-phosphor image plates. Some comparison high-energy images were obtained with both image plates and the a-Si panel and showed equivalent image quality for approximately equal exposure times.