MSE PhD Prospectus Defense: Zhaoyi Zheng

MSE PhD Prospectus Defense: Zhaoyi Zheng

TITLE: Electrodeposition and Functionalization of Reactive Polymer Thin Films for Fast CO2 Direct Air Capture

ADVISOR: Jörg G. Werner ME, MSE

COMMITTEE: Keith A. Brown ME, MSE, Physics; Sean D. Lubner ME, MSE; Chuanhua Duan ME, MSE

ABSTRACT: High direct air capture (DAC) productivity is critical for rapidly reducing CO2 concentrations in both atmospheric and confined environments; however, research investigating sorbent performance across system, structural, and material levels remain limited. This work presented a tunable, hierarchically structured sorbent platform consisting of a porous carbon fiber (CF) integrated with an amine-functionalized polymer ultrathin coating. Porous CF with tailored architectures were engineered to provide interconnected macroscopic pathways that minimize flow resistance and enable efficient gas transport. Poly (glycidyl methacrylate) (PGMA)-based reactive electrodeposition of polymer network (EPoN) was developed to achieve conformal and uniform polymer coatings on complex three-dimensional carbon substrates, with tunable film thickness (tens to hundreds of nanometers) and crosslinking density. The PGMA scaffold enabled systematic tuning of amine density and local chemical environment to simultaneously optimize CO2 binding, regulate water-polymer interactions, and enhance amine efficiency, selectivity, and adsorption rate. A spermine-modified PGMA-coated carbon fiber achieved a CO2 uptake of 1.2 mmol g-1 within 30 min under 400 ppm CO2 and 75% RH, and completed desorption within 5 min, yielding a chemical uptake capacity of 0.89 mmol g-1. Under simulated air, the sorbent maintained stable performance over 40 cycles without observable degradation, indicating the potential to achieve a CO2 removal rate of up to 40.6 mol kg-1 day-1. To establish fundamental processing-structure-property relationships, polymer analysis and discovery array (PANDA), an automated system for high-throughput electrodeposition and functional characterization of polymer films, is employed to screen a library of PGMA thin films prepared under systematically varied electrodeposition conditions. Film thickness, permeability, and chemical reactivity are quantitatively correlated with deposition parameters, enabling rational design of optimized coatings. Moreover, in situ quartz crystal microbalance with dissipation (QCM-D) measurements on planar amine-functionalized PGMA films decouple intrinsic adsorption kinetics from transport limitations, providing direct insight into amine-CO2 reaction rates and polymer network-mediated diffusion. Overall, this study developed amine-functionalized PGMA coated CF with fast kinetics and improved stability, approaching high DAC productivity and offering a novel pathway toward efficient CO2 capture systems.