Metal Loading Effect on the Activity of Co₃O₄/N‐Doped Reduced Graphene Oxide Nanocomposites as Bifunctional Oxygen Reduction/Evolution Catalysts

Abstract

The development of effective and stable reversible oxygen electrodes is of upmost importance for bringing regenerative energy storage and conversion systems to a commercial reality. However, realization of such electrodes is motivated by low activity and instability of the current electrocatalysts working for both water splitting and oxygen reduction. Herein, we report a series of Co3O4/graphene‐based catalysts with different Co mass loadings prepared by using a facile one‐step hydrothermal route. N‐doped reduced graphene oxide (NRGO) was utilized as a substrate for the deposition of oxide particles. The structural properties and surface composition of the different materials were investigated by powder X‐ray diffraction, transmission electron microscopy, and X‐ray photoelectron spectroscopy measurements. The effect of Co mass loading on the morphostructural properties of oxide nanoparticles and also on their electroactivity towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was addressed. This study revealed the optimum range for metal loading on the graphene substrate. Co3O4/NRGO with a Co mass loading of 30 wt.% exhibits the highest activity towards ORR and OER, with a reversibility criterion of 763 mV. This work is very helpful for the electrocatalysis community, and will allow effective catalysts to be developed for high‐power metal/air battery or regenerative fuel cell systems, based on earth‐abundant and scalable electrocatalysts.

Advanced graphene-based (photo & electro) catalysts for sustainable & clean energy technologies

“…Kumar et al used a simple hydrothermal approach to create a composite of cobalt oxide and nitrogen-doped reduced graphene oxide (Co 3 O 4 / NrGO). 570,571 Raman spectroscopy revealed peaks for the sp 3 carbon at 1180 cm À1 , the disordered carbon D band at 1350 cm À1 , the amorphous sp 2 carbon at 1540 cm À1 , the E 2g mode at 1590 cm À1 , and the intercalation in graphite at 1620 cm À1 . The XPS analysis confirmed that C, N, O, and Co were present in the composite.…”

Graphene-based materials as electrocatalysts for the oxygen evolution reaction: a review

“…Kumar et al fabricated a cobalt oxide/nitrogen-doped reduced graphene oxide composite (Co 3 O 4 /NRGO) via a simple hydrothermal method. 84 Raman spectroscopy exhibited a peak at 1180 cm −1 , corresponding to the sp 3 carbon, a peak at 1350 cm −1 , corresponding to the D band of disordered carbon, a peak at 1540 cm −1 , corresponding to the amorphous sp 2 carbon, G band at 1590 cm −1 , corresponding to the E 2g mode, and D band at 1620 cm −1 , corresponding to the intercalation in graphite. The XPS study confirmed that the composite contained C, N, O, and Co.…”

Facile Synthesis of Mesoporous Co3O4/CoO on rGO Nanocomposites as Highly Active and Stable Oxygen Bi-Functional Electrocatalysts

“…The cobalt oxide morphology can be easily tuned by controlling the precipitation of the corresponding precursors through varying the pH value governed by urea concentration [27]. The oxygen functionalities grafted onto GO surface (e.g., −COOH, −OH) act as ligands enabling the nucleation and growth of the cobalt oxide precursor, which leads to a strong affinity of the as-grown mesoporous cobalt carbonate and the GO surface [1,18]. Besides, during the hydrothermal treatment, GO is chemically reduced to rGO.…”

“…The binding energy of Co 2p3/2 and Co 2p1/2 photopeaks at 780.0 and 794.5 eV with energy difference of 15.2 eV indicates the co-existence of Co 2+ and Co 3+ species on the surface of the material [28]. Herein, the Co 2p spectra were processed and decomposed using two reference spectra corresponding to commercial Co3O4 (red curve) and CoO (green curve) materials [18,29]. For all the samples, the obtained spectra can be expressed as a linear combination of spectra recorded for these two reference materials, confirming therefore that the materials are composed of hybrids Co3O4-CoO.…”