The Mallouk Group is interested in several problems in materials chemistry, including photoelectrochemistry, electrochemical energy conversion, low-dimensional physical phenomena, and motion on the nanoscale. Our approach involves the synthesis of materials that contain molecular and/or solid state components, and the study of their structure, assembly, and properties by a variety of physical techniques.
Overview of current research projects in the group
Solar and Electrochemical Energy Conversion. An important goal of this aspect of our research is to develop new kinds of nanomaterials that will lead to more efficient and less expensive energy conversion devices. Dye-sensitized solar cells, developed over three decades ago by Michael Gratzel and coworkers, generate electricity from sunlight through light absorption by molecular dyes. By incorporating catalysts that enable water oxidation into dye sensitized solar cells, it is now possible to split water to hydrogen and oxygen using visible light. We use biomimetic principles to control electron and proton transfer reactions in these cells and transient electrochemical and spectroscopic techniques to measure their kinetics. These studies have recently led to a better understanding of system-level problems in the photoelectrolysis of water, to the design of more efficient electrolyzers for converting CO2 to fuels and chemicals, and to novel membrane and electrocatalyst concepts for alkaline fuel cells and redox flow batteries. The Mallouk group is part of the CHASE solar fuels hub project, and the CABES energy frontier research center on alkaline electrochemistry.
Nanowires and Nanomotors. Several projects in the group use porous membranes and colloidal crystals as templates for making nanomaterials. In collaboration other research groups at Penn and Penn State, we are studying the movement of asymmetric metallic and semiconducting nanoparticles that are powered by spontaneous catalytic reactions. These catalytic swimmers were the first examples, outside of biological systems, of autonomously powered nano- and micromotors. In many ways, they resemble living microbial motors and exhibit similar kinds of collective behavior. The principles of catalytically driven movement have now been used to design microscale pumps and rotors, and to study the powered motion of individual enzyme molecules. In collaboration with colleagues at ESPCI in Paris, we discovered that micron-size metal “rockets” undergo a range of autonomous and cooperative motion when propelled by acoustic waves. Microswimmers that contain on-board acoustic resonators can be propelled at remarkable speeds and with directional control in three dimensions. These new swimmers are biocompatible and function at ultrasonic power densities that are typically used in medical imaging.
Layered and Porous Inorganic Solids. We are developing a set of soft chemical reactions that topochemically interconvert different structural families of layered and three-dimensionally bonded oxides. Layer perovskites, metal phosphates, clays, and other lamellar solids can be grown layer-by-layer and converted to other interesting nanoscale morphologies (such as nano-scrolls and tubes) by means of intercalation, exfoliation, and restacking reactions. We are devising new ways to intercalate and exfoliate metal dichalcogenides, boron nitride, and graphite, without using redox cycles that damage the sheets. These unilamellar compounds are of particular interest as novel low-dimensional electronic conductors, as catalyst supports, as electrode materials for batteries, and as ionic conductors. In collaboration with research groups at Penn, Penn State, and other institutions, we are also synthesizing and studying the emergent properties of materials that are porous on different length scales. We use porous colloidal crystals as templates to synthesize and study metalattices of semiconductors, ferromagnets, and other materials.
Positions Available. We are currently seeking applications for two postdoctoral fellows who will work on our DOE-supported projects on photochemical and electrochemical energy conversion.
The Mallouk group includes high school students and teachers, undergraduates, graduate students, and postdoctoral fellows who work on a diverse set of intellectually stimulating research projects. Please see the links below for scholarships and fellowships that support student, teacher, and postdoctoral research at Penn.
Undergraduate students can receive independent study credit for research by registering for Chem 299 (freshman/sophomore) or 399 (junior/senior). Please click here for details.
National Science Foundation GRFP
National Defense Science and Engineering Fellowship (NDSEF)
United Negro College Fund (UNCF)
National Organization for the Advancement of Black Chemists and Chemical Engineers (NOBCChE)
Penn’s Postdoctoral Fellowship for Academic Diversity program
VIEST Postdoctoral Fellowship
High School Teachers:
Research Experiences for Teachers
Mutual Respect and Cooperation. We are committed to following the code of mutual respect and cooperation. The 12 principles of the code are:
- Treat everyone equally and with respect
- Be courteous
- Be ready to communicate
- Encourage others and share your expertise
- Give and accept constructive criticism
- Be receptive to change
- Be a team player
- Get involved
- Have a positive attitude
- Be honest and accept responsibility
- Recognize other people’s priorities
- Strive to do your best