Synergistic effect of tunable oxygen-vacancy defects and graphene on accelerating the photothermal degradation of methanol over Co3O4/rGO nanocomposites

A series of Co3O4/rGO (reduced graphene oxide) nanocomposites with tunable oxygen vacancy defect concentrations were synthesized via a simple alkali etching and applied for photothermal degradation of methanol. In the samples without alkali etching, the Co3O4/rGO nanocomposite showed higher photothermal catalytic performance than Co3O4 due to the thermal auxiliary effect of rGO. Among the Co3O4/rGO nanocomposites, the nanocomposite etched by 0.64 g NaOH (denoted as Co3O4/rGO-N0.64) exhibited the highest photothermal catalytic performance (methanol conversion of 96%, CO2 yield of 91%) as well as excellent durability under the solar irradiation. The superior activity was mainly attributed to the synergistic effect of the thermal auxiliary effect of rGO and the abundant oxygen vacancy defects. The reaction mechanism confirmed that both of gas phase oxygen and lattice oxygen were activated and participated in this reaction process. The enrichment of oxygen vacancy defects in Co3O4/rGO-N0.64 can boost the circulation of oxygen species, which played a crucial role in the continuous and effective photothermal catalytic oxidation of methanol.