The objective of this project is to study nanomanufacturing technologies to produce high-quantity graphene with drastically low cost and high efficiency for energy conversion and storage. Clean and sustainable energy technologies, such as fuel cells, metal-air batteries and water-splitting, are currently under intensive research and development because of their high efficiency, promising large-scale applications, and virtually no pollution or greenhouse gas emission. At the heart of these energy devices, there are critical chemical reactions that determine the efficiencies of energy conversion and storage. These reactions, however, are sluggish and require noble metal catalysts (e.g., platinum). The limited resources and high cost of platinum have hampered the commercialization of these technologies. Carbon nanomaterials have been demonstrated to be promising metal-free catalysts to replace expensive noble metals in fuel cells, metal?air batteries and water-splitting. However, there is a lack of design principles or descriptors to quantitatively predict the catalytic activities of carbon nanomaterials. To accelerate the search for highly active metal-free carbon-based catalysts, it is critical to identify a descriptor for correlating material structures to its catalytic activity. In this project, we have demonstrated that catalytic activities for various carbon-based materials primarily correlate to their structures. Such descriptors have predictive power to provide insights into the structure-activity relationship and enabled us to effectively design new catalysts with enhanced activities.

Intellectual Merits: We have developed a series of atomic models for different materials to describe their catalytic activities in fuel cells to generate electricity, metal-air batteries to store electric energy, and water splitting for hydrogen generation. The materials studied in this project includes doped carbon nanomaterials, doped carbon nitrides, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and core-shell metal structures. The electronic structures and reaction pathways on these materials were calculated systematically by the density functional theory (DFT) method to predict their electrocatalytic activities. Descriptors and design principles for different materials have been developed to accurately predict the electrocatalytic activities. The descriptor includes the dopant and its bonding environmental information, which provides detailed guide to the rational design and screening of high-performance catalysts. A ?volcano? relationship between the descriptor and the electrocatalytic activity was established, from which the most active dopant elements and related structures were identified. The design principles provide a theoretical base for catalysis science and can be used as a powerful guidance to develop various new earth-abundant, cost-effective catalyst materials.

Broader Impacts: This work should open the door to the rational design and nanomanufacturing of novel highly-efficient catalysts for clean energy technologies such as fuel cells, metal-air batteries and water splitting. The new materials design concepts, computer codes, and computational methods developed in this project can potentially be used for the design of new cheaper, effective catalysts. This will promote the commercialization of the clean energy technologies by lifting the barrier to the technologies hindered by expensive noble metal catalysts.

      The participating students at all levels, including high school students, undergraduate and graduate students, were trained to do cutting-edge research. Under the support of the NSF grant, two graduate students have directly been involved in this research, and both of them completed their dissertation and obtained their PhD degree.  Students from under-represented groups were encouraged to participate in the research. Two high school students have been involved in the research in PI?s labs. The research activities in PI?s lab fostered their interest in science, engineering and technology, and as a result, all of them have selected engineering as their college major. The participation of high school students in our research results in more outreach in our society and broaden social network with their parents, which benefits the society. Two book chapters have been published, and 20 papers have been published in top scientific journals. The project also yielded two PhD dissertations. The related work has been presented in national and international conferences.

Last Modified: 05/10/2019
Modified by: Zhenhai Xia