We carried out computational simulations to further understand the mechanism of VC-GO reduction. The mechanism of VC-GO reaction has been reported previously, where hydroxyl and epoxy groups on GO are mainly removed by VC, however, the detailed reaction processes are still unclear. Here, we performed density functional theory (DFT) calculations to gain insights into the mechanism of the reduction. These calculations were performed using the PW6B95-D3BJ exchange-correlation functional, which has been extensively benchmarked and found to provide excellent performance for both reaction energies and barrier heights. For full computational details, see the Supplementary note 2. The Gibbs free potential energy surface (PES) in a simulated aqueous environment is shown in Figure , as well as the located local minima and each transition structure. Gibbs free reaction energies (∆G298) and barrier heights (∆G ‡ 298) are given relative to the separated VC and GO nanosheet with a single epoxy functional group (labeled as free reactants). We find that the reduction of the epoxy group proceeds via a multistep reaction mechanism, which involves two consecutive proton transfers associated with relatively low-lying transition structures. The barrier for the first proton transfer (TS1) is 54.2 kJ/mol relative to the free reactants, while that of the second proton transfer (TS2, can be considered as the reduction of hydroxyl group on GO) is 55.6 kJ/mol, which is practically barrierless relative to the intermediate complex (IC) formed in the first step (see Figure ). Accordingly, there is no clear rate-determining step in this stepwise reaction mechanism. The final step is highly exergonic, which provides the entire reaction the thermodynamic driving force, also noticing the product complex shows dramatically lower energy as much as 173.1 kJ/mol than the free reactants. The computational results demonstrate that the reduction of GO with VC is a highly exergonic process associated with low-lying transition structures and will therefore proceed rapidly at room temperature.