Water ozone decomposition in graphitic and graphene based catalytic materials: Kinetics of catalyst deactivation

Decomposition of ozone in water in the presence of five different materials based on graphene and graphite has been studied with the aim of stablishing the catalytic reaction and catalyst deactivation kinetics of paramount importance in treatment sustainability, catalyst design optimization, risk assessment and economics. Ozone is considered as a poison of the catalytic process and, as a consequence, catalyst deactivation has been assumed to be dependent on the ozone concentration. An apparent activity property has been considered as the ratio of decomposition rates of ozone at any time and that at start of reaction. Among materials studied, commercial graphene presents the highest catalytic capacity to decompose ozone due to its high surface area and pore volume. Ozone treatment of graphene to increase surface oxygen groups does not lead to any significant advantage. Due to nearly null surface area and pore volume, commercial graphite gives rise to a slight increment of ozone decomposition rate if compared to the free catalytic decomposition run. Ball milling of graphite leads to an increase of catalytic ozone decomposition that is further increased with a subsequent ozone treatment. In both graphite -based materials, an increase of surface oxygen groups and pore volume was observed. However, catalyst activity of graphene materials was much higher. The kinetics study leads to determine rate constants of both catalytic ozone decomposition reaction and catalyst deactivation. These rate constants follow a potential relationship with catalyst concentration in the range 0.01 to 0.15 g L-1.