Chemical modification of graphene oxide for CO2 capture: Impact on structure, defects, and adsorption behavior

Abstract

Graphene oxide (GO) and its chemically modified derivatives (mGO) offer tunable surface chemistry and processability for CO2 adsorption, yet the individual roles of heteroatom doping and film architecture remain unclear. In this study, the objective was to systematically decouple and quantify the impact of two factors on the reversible CO2 uptake in GO-derived thin films: (i) chemical structure, via water, nitrogen and sulfur functionalization, and (ii) film morphology, via controlled mass loading. The objective of the present study was to ascertain how these factors influence reversible CO2 uptake in GO-derived thin films. The GO was synthesized by Tour´s method and identical low-temperature hydrothermal treatments were applied, using N- and S-precursors. A range of analytical techniques, including UV–Vis, FTIR, Raman, XPS, and SEM characterization were utilized to map alterations in surface functionality, defect density, and film topology. Concurrently, a quartz crystal microbalance was employed to measure CO₂ uptake (3–50 Torre) on films deposited at 2 600–20 600 µg/cm². Whilst the present study does not aim to deliver a record‑setting adsorbent for real‑world deployment, we did observe that nitrogen‑doping (4.5 at % N, C/O = 4.0–5.1) introduces Lewis‑basic sites that increase uptake to 1.25 wt % at 45 Torr, whereas sulfur‑modification yields moderate gains through enhanced porosity. Varying film mass revealed that thicker deposits prolong equilibration, identifying an optimal thickness for balanced capacity and kinetics. These mechanistic design rules clarify how isolated modifications in chemical functionality and physical architecture control CO2 capture under rigorously controlled conditions.