Water splitting activity of oxygen-containing groups in graphene oxide catalyst in bipolar membranes

Graphene oxide (GO) is a very effective catalyst for splitting water into H⁺ and OH⁻ ions in bipolar membranes. This research investigated the catalytic activity of six oxygenated functional groups in GO for water splitting. Møller-Plesset second order perturbation method (MP2) simulations were performed to calculate activation barriers for proton acceptance and release reactions with and without an applied electric field. The relative catalytic activity for the functional groups on GO was independent of the electric field intensity and dielectric constant. The catalytic activity for accepting and releasing a proton linearly correlated with the pK_a of the functional groups. The edge carboxylate site had the highest catalytic activity for water splitting, and had activation barriers that were 0.2 to 0.4 kcal/mol higher than a model tertiary amine. This suggests that the high catalytic activity of GO results from a high catalytic site density, as opposed to a chemical effect.