This study investigates the thermal deoxygenation process of graphene oxide (GO) using high-resolution in situ X-ray photoemission and X-ray absorption spectroscopies. The research aims to understand the evolution of the electronic structure and the survival rate of oxygen-containing functional groups during thermal reduction. Key findings include: 1. **Edge Plane Carboxyl Groups**: These groups are highly unstable and are the first to be removed during thermal reduction. 2. **Carbonyl Groups**: These groups are more difficult to remove and persist at higher temperatures. 3. **Phenol Groups**: These groups form through the reaction of basal plane epoxide groups with adjacent hydroxyl groups at moderate temperatures (~400 °C) and survive even at 1000 °C. 4. **Density of States (DOS)**: A significant increase in DOS near the Fermi level is observed at 600 °C, indicating the progressive restoration of aromatic structure in thermally reduced GO. The study provides a comprehensive understanding of the thermal deoxygenation process and the electronic changes in GO, which is crucial for optimizing reduction processes and advancing applications in nanoelectronics.This study investigates the thermal deoxygenation process of graphene oxide (GO) using high-resolution in situ X-ray photoemission and X-ray absorption spectroscopies. The research aims to understand the evolution of the electronic structure and the survival rate of oxygen-containing functional groups during thermal reduction. Key findings include: 1. **Edge Plane Carboxyl Groups**: These groups are highly unstable and are the first to be removed during thermal reduction. 2. **Carbonyl Groups**: These groups are more difficult to remove and persist at higher temperatures. 3. **Phenol Groups**: These groups form through the reaction of basal plane epoxide groups with adjacent hydroxyl groups at moderate temperatures (~400 °C) and survive even at 1000 °C. 4. **Density of States (DOS)**: A significant increase in DOS near the Fermi level is observed at 600 °C, indicating the progressive restoration of aromatic structure in thermally reduced GO. The study provides a comprehensive understanding of the thermal deoxygenation process and the electronic changes in GO, which is crucial for optimizing reduction processes and advancing applications in nanoelectronics.