Comparative Study of the Catalytic Activities of Three Distinct Carbonaceous Materials through Photocatalytic Oxidation, CO Conversion, Dye Degradation, and Electrochemical Measurements

Abstract

In order to compare the catalytic activities of reduced graphene oxide (rGO), graphene oxide (GO), and graphene, we conducted oxidation of 2-aminothiophenol (2-ATP) and reduction of nitrobenzene (NB) in their presence by using high-resolution photoemission spectroscopy (HRPES). In addition, we determined conversion rates of CO to CO₂ in the presence of these catalysts by performing a residual gas analyzer (RGA) under a UHV condition, Orange II and methylene blue degradations UV-vis spectrophotometry, and electrochemistry (EC) measurements in an aqueous solution, as well as by obtaining cyclic voltammograms and determining the change of the condition of electrodes before and after the oxidation of 2-ATP. We found that we can successively fabricate GO (oxidation) and graphene (reduction) from rGO by controlling the oxidation or reduction procedure time and then clearly comparing the critical properties among them as we perform various oxidation and reduction activities.

Figure 1

SEM and TEM images of (a,d) rGO, (b,e) GO, and (c,f) graphene, respectively at 300 K.

Figure 2. XRD patterns of the fabricated carbon based materials.

(a) rGO, (b) GO, and (c) graphene.

Figure 3

(Top panel) Raman spectra acquired at 300 K of the (a) rGO, (b) GO, and (c) graphene samples spin-coated onto silicon substrates and their corresponding optical images. (Bottom panel) HRPES measurements of the C 1s and O 1s core level spectra of the (d,g) rGO, (e,h) GO, and (f,i) graphene samples prepared on silicon substrates at 300 K.

Figure 4

(Top panel) HRPES measurements of the S 2p core level peaks of (a) 360 L 2-ATP adsorbed on rGO, (b) 360 L 2-ATP adsorbed on GO, and (c) 360 L 2-ATP adsorbed on graphene at 300 K, and of the N 1s core level peaks of (a) 360 L NB adsorbed on rGO, (b) 360 L NB adsorbed on GO, and (c) 360 L NB adsorbed on graphene at 300 K. (Bottom panel) Plots of the ratios of S3 (sulfoxide group) to S1 (thiol group), which indicate the photocatalytic activities of the samples in the oxidation of 2-ATP (left panel) and those of the ratios of N2 (aniline group) to N1 (nitro group) via the reduction of NB (right panel) as a function of molecular exposure under 365 nm UV light.

Figure 5

(Top panel) Mass spectra obtained from RGA of (a) rGO, (b) GO, and (c) graphene grown on silicon substrates after co-exposure to O₂ and CO gas (1 × 10⁻⁶ torr) at 300 K. (Bottom panel) The variations with substrate temperature in the rates of conversion of CO to CO₂ gas on (d) rGO, (e) GO, and (f) graphene.

Figure 6

(a) Degradation of Orange II (0.15 mM) and (b) methylene Blue (0.15 mM) with GO, rGO, and graphene.

Figure 7

CVs of 20 mM 2-ATP were obtained on (a) rGO, (b) GO, and (c) graphene modified glassy carbon electrodes in 50 mM tris buffer at a scan rate of 100 mV/s. Optical microscopy images before and after the reaction: (d,e) rGO, (f,g) GO, and (h,i) graphene.