The Fluid Interface Reactions, Structures and Transport (FIRST) Energy Frontier Research Center

The overarching goal of the FIRST Center, which is in its sixth year of operation, is to develop fundamental understanding and validated, predictive models of the unique nanoscale environment at fluid-solid interfaces, that will enable transformative advances in electrical energy storage and electrocatalysis. The Center is primarily based at Oak Ridge National Laboratory, and includes research at Argonne National Lab, Drexel, Penn State, Vanderbilt, and the Universities of California at Davis and Riverside, Delaware and Minnesota.  In order to achieve our goal, we integrate novel substrate and electrolyte synthesis and characterization, advanced electron (TEM) and scanning probe microscopies (SPM), neutron and X-ray scattering, and multiscale computational modeling ranging from quantum Monte Carlo to classical density functional theory approaches. Electrolytes investigated include aqueous, polar organic and room temperature ionic liquids (RTILs), representing increasing cost and electrochemical stability, and decreasing viscosity, competing factors in device performance, where charge/discharge rates are affected by viscosity, while stored energy in electrochemical capacitors increases with the square of the applied potential.  Organic solvents have the added problem of high volatility and flammability.  We investigate the interactions of these fluids with a wide range of carbon materials and recently an entirely new class of 2D transition metal carbonitrides, known as MXenes.  Like graphenic materials, MXenes can be conductive, but they can also be strongly hydrophyllic and well-suited for multivalent ion adsorption and intercalation.  Our recent efforts have focused on predicting the functionality of interfacial systems for capacitive and pseudocapacitive electrical energy storage in microdevice to grid scale applications.  The structures, dynamics and transport properties of RTILS at planar, curved and enclosed (nanopore) surfaces is intensely investigated, and we have begun investigating the role of imidazolium RTIL cations in co-catalyzing the highly efficient and selective electrocatalytic conversion of CO₂ to CO at negatively charged, post-transition-metal electrode surfaces as a first step in Fischer-Tropsch-type processes for converting CO₂ to liquid fuels and chemical feedstocks. Unique contributions of the FIRST Center include the development of 1.) Electrochemical Strain Microscopy, an SPM method that probes the expansion and contraction of both battery and nanoporous electrochemical capacitor electrodes during charging/discharging with nanometer spatial resolution; 2.) in situ, operando electrochemical flow cells S/TEM studies of ion transport and interfacial reactivity with subnanometer resolution; 3.) unique applications of neutron scattering to probe the structures and transport properties of fluids within hierarchical pore systems; 4.) onion-like carbon nanoparticles with sphereical external surfaces and graphite-like conductivity and inertness; 5.) defect-driven and selective transport of protons across large, pristine single-layer graphene sheets via a Grotthus mechanism; 6.) Electrochemical Flow Capacitor systems for grid scale applications; 7) coarse-grained models like classical density functional theory and reactive classical MD force fields to achieve fundamental and predictive understanding of interfacial system functionality at larger time and length scales; and 8.) efficient lower temperature and/or less toxic synthesis routes for a wide array of ultrahigh surface area carbon and MXene materials.