Co₃O₄/rGO Catalysts for Oxygen Electrocatalysis: On the Role of the Oxide/Carbon Interaction

Abstract

The reduction degree of graphene oxide substrate governs the activity and stability of Co 3 O 4 /rGO nanocomposites toward oxygen reduction reaction and oxygen evolution reaction. In this work, Co 3 O 4 nanoparticles with narrow size distribution were uniformly deposited onto graphene oxide materials with different reduction degrees, by using a microwave-assisted hydrothermal method. The physicochemical characterization of these nanocomposites indicates that oxygenated groups grafted onto a reduced graphene oxide surface allow creating strong interactions between the carbon-based substrate and Co 3 O 4 nanocrystals. The obtained results denote that the electrocatalytic activity and stability of these nanocomposites toward the ORR and OER depend on the entanglement between the strength of the carbon/oxide interaction and the electronic conductivity of the substrate.

Fe-Modified Pd as an Effective Multifunctional Electrocatalyst for Catalytic Oxygen Reduction and Glycerol Oxidation Reactions in Alkaline Media

“…To this end, Raman spectroscopy experiments were performed and the obtained Raman spectra were decomposed using pseudoband Voigt functions. Figure d–g shows that the analyzed materials exhibit the same profiles, in agreement with previous reports. ,,, Table outlines the data of interest. The graphitic G-band (G-mode, E 2g symmetry) is characterized by the peak at 1590 cm –1 (CC stretching, sp 2 -bonded C in-plane vibration, area A G ).…”

“…The graphitic G-band (G-mode, E 2g symmetry) is characterized by the peak at 1590 cm –1 (CC stretching, sp 2 -bonded C in-plane vibration, area A G ). On the other side, the band situated at 1320–1330 cm –1 is named the D-band (or D-mode, A 1g symmetry, area A D ), which is typical of the symmetry breakdown for edge C of sheets and growth when the number of defects increases in graphene lattices. ,,, The obtained values of A D / A G = 2.9 (GO), 2.3 (rGO), 2.3 (Vulcan-p), and 2.7 (Vulcan) indicate a slight change of the graphitization upon the reduction of GO or the thermal treatment of Vulcan. Correspondingly, the deduced value of L a (nm) = 15.5 (GO), 19.4 (rGO), 19.4 (Vulcan-p), and 16.8 (Vulcan) shows a modification, which suggests that the long-distance-order sp 2 group size was adversely impacted by the reduction of GO or by the heat treatment of Vulcan-p …”

“…Figure 1d−g shows that the analyzed materials exhibit the same profiles, in agreement with previous reports. 25,27,39,40 Table 1 outlines the data of interest. The graphitic G-band (G-mode, E 2g symmetry) is characterized by the peak at 1590 cm −1 (CC stretching, sp 2 -bonded C inplane vibration, area A G ).…”

“…By XRD calculation, the fabricated rGO is 1.5 nm thick, that is, four sheets. However, given the low BET surface of GO-based materials compared to other reported systems (tens to hundreds of m 2 /g), the later data by XRD are underestimated because we observed in several TEM images (Figure S4) that the thickness is not so homogeneous, leading to a much higher number of layers on some parts . Having physiochemically characterized the two supports of rGO and Vulcan, we next sought to get, in a first attempt, the crystallinity and crystallographic structure of the as-synthesized four types of nanomaterials Pd/Vulcan, PdFe/Vulcan, Pd/rGO, and PdFe/rGO.…”

Morphological and Structural Evolution of Co3O4 Nanoparticles Revealed by in Situ Electrochemical Transmission Electron Microscopy during Electrocatalytic Water Oxidation

“…The Co3O4 nanoparticles were produced through a microwave-assisted hydrothermal synthesis by modifying a protocol reported recently. 44 From a low-magnification image, we calculate the total area of the rod-like working GC electrode (Figure 1) to be ~2.8 10 -5 cm 2 . Its thickness is 60 nm.…”