Facile synthesis and characterization of γ-Al2O3 loaded on reduced graphene oxide for electrochemical reduction of CO2

Electrocatalytic reduction of CO2 to valuable organic compounds and fuels using energy efficient techniques is presently of great importance. In this work, we show the synthesis of Al2O3-decorated reduced graphene oxide (rGO) electrocatalysts and their catalytic properties for the conversion of CO2 into formate. These hybrid nanostructured materials are prepared using chemical synthesis, followed by chemical vapor deposition. The materials are characterized by X-ray diffraction and Raman spectroscopy, and the results confirm the formation of gamma-Al2O3 on defect-rich rGO. Transmission electron microscope images reveal the formation of gamma-Al2O3 with particle sizes of 8 +/- 0.3 nm on rGO sheets that are similar to 100 x 100 nm in length and width and composed of a few-layers of graphene. X-ray photoelectron spectroscopy confirms the presence of Al-O, C-C and C-O bonds in the material. The amount of Al is similar to 2.8%, as determined by inductively coupled plasma-mass spectrometry (ICP-MS). The material catalyzes the electrochemical reduction of CO2 at a potential of -0.434 V vs. RHE in 0.5 M KHCO3 solution, which is used as an electrolyte. The potential dependent bulk electrolysis shows that the reduction product is formate, which formed with a faradaic efficiency (FE) of 31.90, 37.25, 42.50, 55.10 and 91.20% at potentials of -0.434, -0.534, -0.634, -0.734 and -0.934 V vs. RHE, respectively. Based on these findings, these noble metal-free electrocatalysts may find industrial applications to convert CO2 into valuable chemicals, and thereby to mitigate CO2-related global warming issues.