Thermal Annealing Process, Water Storage, and Water Permeation Application of Graphene Oxide Membranes

Zong Jhe Hsieh^1*, Chueh Cheng Yang², Chia Hsin Wang², Ping Hung Yeh¹, Cheng Hao Chuang¹

¹Department of Physics, Tamkang University, New Taipei City, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Zong Jhe Hsieh, email:8888jojo@gmail.com

The in-situ environmental experiment is important to monitor the chemical de-oxidation and re-modification of reduced graphene oxide (rGO) due to the controllable adjustment of the surface functional groups of graphene oxide (GO). For scientific purposes, a perfect hexagonal ring of gra-phene (G) that exhibits various oxidation sites is crucial for inducing different chemical bonding responses and is effective for external gas molecules. A membrane composed of G/GO/rGO mate-rials has been fabricated for potential energy and electrical applications, as described in the report. Using ambient pressure X-ray photoelectron spectroscopy (AP-XPS), we observe the thermal evolu-tion and re-oxidation behavior of thermally reduced graphene oxide (Th-rGO) under various at-mospheric and humidity conditions. The thermal process was heated from room temperature to 300 °C in increments of 50 °C under ultra-high vacuum (5 × 10⁻⁶ mbar) and in simulated air (0.6 mbar, 80% N₂ / 20% O₂), in order to introduce the thermal energy and gas interaction into the GO mem-brane. In a vacuum environment (Th-rGO-Vac), the C–O–C and C=O groups decompose primarily as the temperature increases. Meanwhile, the C-OH and O=C–OH groups have higher ratios at low-er temperatures, but these ratios decrease after reaching 150°C. In a simulated air environment (Th-rGO-Air), C–O–C, C=O, and C-OH also decompose directly, but only the O=C–OH group has a crossover behavior during the thermal annealing process. In the water storage application, following thermal annealing in ultra-high vacuum and simulated air, an increase in water gas pressure (0.1–0.6 mbar) was applied to the same Thr-GO membranes during the AP-XPS experiment. The pro-nounced chemical bonding and bonding transfer have been observed in both the Th-rGO mem-brane with rising vapor pressure, primarily through the formation of C-O-C and C–OH groups. Even at pressures as low as 0.1 mbar, the surface of Th-rGO-Air is already saturated with adsorbed water molecules, highlighting strong water–surface interactions. In contrast, the Th-rGO-Vac mem-brane offers higher water gas storage and better chemical bonding states than the Th-rGO-Air, mak-ing it suitable for recyclable energy applications. AP-XPS experiments were conducted using the liquid cell membrane, with the main chamber maintained under ultra-high vacuum and at three dif-ferent nitrogen pressures (0.1, 0.3, and 0.6 mbar). The key aspect is to determine the rate of water molecule permeation through the GO membrane based on the pressure gradients between the main chamber and the liquid chamber. These findings reveal the crucial role of atmospheric gases and water vapor in modulating the surface chemistry and electronic properties of rGO, offering insights for sensing and electronic tuning applications.

Keywords: Graphene Oxide, Thermal reduction, Ambient Pressure - XPS, Re-oxidation, Humidity response