CAS: Green Graphitic Carbon from Natural Precursors Using Graphene Oxide Additives: A Combined Experimental and Atomistic Approach

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Non-technical summaryGraphite is a critical raw material for the green transition and demand is increasing in markets including electric vehicles and green energy storage. Based on current production, demand from these markets will result in a significant supply shortfall unless new sources are identified. Unfortunately, petroleum-derived graphite is a nonrenewable resource and requires intensive energy for conversion to graphite while the supply of mined graphite is limited and insufficient to meet the growing demand. In contrast, bio-based resources (e.g., the lignin byproduct from papermaking, cellulosic materials) are renewable and sustainable precursors for conversion into graphite but these bio-based precursors contain oxygen which fosters non-graphitizing structure. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Professors Randy Vander Wal and Adri van Duin and their research groups at Penn State University will explore an innovative process towards the graphitization of bio-based precursors called reactive templating in which graphene oxide additives and controlled heating will enable the formation of desired graphitic crystalline structure. Atomistic-scale simulations will be used to identify time and temperature constraints for this template-assisted conversion into graphite. The templated conversion may also lower the temperatures required for conversion of bio-based materials into graphite, saving energy while reducing CO2 emissions associated with the manufacturing. This project promotes K-12 STEM by contributing demonstrations to science camps held during summers at Penn State and developing science engagement activities for after-school events. By hosting first year women undergraduates during the academic year this project contributes to diversity in the STEM pipeline. Instructional materials for secondary and post-secondary educators contribute to workforce development. You tube videos highlighting the high temperature material conversion into graphite facilitates public connections with the research. Engagement of an industrial advisor on the project provides market-based feedback to the project.Technical summaryGraphitic carbons are ideally suited as electrode materials for battery-based energy storage systems given their low cost, high electrical conductivity, stable physicochemical properties, and long cycle life. A bio-based, renewable and sustainable precursor would displace the oil or coal derived compounds presently used in the manufacture of carbons for energy storage while reducing CO2 emissions associated with their production. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, investigates the hypothesis that the addition of graphene oxide to biopolymers redirects the carbon structure from non-graphitizing to graphitizing during high temperature treatment stages. The postulate is that the biopolymer matrix radicals cross-link with those on the graphene oxide, rather than with other biopolymer sited radicals, thereby templating to the graphene oxide and forming graphitic structure upon higher heat treatment. The targeted biopolymers include cellulose and extracted lignin, which are both commercially available. The timescales and temperatures over which structure emerges are delineated by a combined experimental and atomistic-scale simulation approach. Reactive molecular dynamics simulations reveal the underlying mechanistic steps and relative contributions of biopolymer type, O-atom content on GO, and explore reaction parameters such as temperature over a far broader space than experimentally feasible, therein providing further experimental guidance for component fractions and elemental contents. This study also contributes the first direct comparison between carbon graphitization kinetics via high resolution transmission electron microscopy (HRTEM) and atomistic model simulations—with connection to electrical conductivity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.