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The connection between the active components and supports in a catalyst is important for the high activity and long‐term stability during catalysis. Here, Co3O4 nanoparticles embedded in F, N‐doped graphene (Co3O4/F, N‐doped G) are synthesized by silicon‐hydrogen bond reduction. F and N atoms doped graphene interacts with Co3O4 nanoparticles to optimize oxygen reduction reaction (ORR) catalytic activity. The optimal Co3O4/F, N‐doped G‐2 catalyst with Co loading of 3.38 wt% shows a half‐wave potential of 0.852 V vs RHE in 0.1 M KOH solution. Furthermore, Co3O4/F, N‐doped G‐2 catalyst outputs an extremely high open circuit voltage of 1.47 V and an excellent power density of 280 mW cm−2 at current density of 450 mA cm−2 when applied to the primary Zn‐air batteries. Due to the synergetic effects from Co3O4 and supports (F, N‐doped G), Co3O4/F, N‐doped G‐2 catalyst also shows excellent stability and anti‐toxicity, and has good practical application prospects. [ABSTRACT FROM AUTHOR]

[Display omitted] • The facile and outstanding route were introduced for decorating Co 3 O 4 on GQDs to form the X% (Co 3 O 4)/GQDs composites. • The Co 3 O 4 nanoparticles with ultra-small sizes were uniformly decorated on the GQDs. • The resultant composites are applied as the robust photocatalysts for the conversion of N 2 to NH 3. • The kinetics and the concentration of produced ammonia on the surface of X% (Co 3 O 4)/GQDs composites were studied in details. • The mechanism of ammonia production is discussed in details. The crises related to energy and pollutants in the present century have led to the special look toward clean and sustainable energies. Material science plays a significant role in the way to achieve the world's envisioned sustainability. This paper introduces an outstanding and facile route for decorating cobalt oxide (Co 3 O 4) on graphene quantum dots (GQDs) to form the X% (Co 3 O 4)/GQDs composites. The 5% Co 3 O 4 /GQDs, 10% Co 3 O 4 /GQDs, and 20% Co 3 O 4 /GQDs composites are formed with the aid of ultrasound irradiation, followed by the pyrolysis of citric acid employing a bottom-up approach. Decoration of Co 3 O 4 nanoparticles with various weight percentages of 5%, 10%, and 20% is uniformly performed into the GQDs with the size distribution of 4.4, 4.6, and 4.8 nm, respectively. The resultant composites are applied as the robust photocatalysts for the conversion of N 2 to NH 3. In this report, GQDs decorated by three ratios of 5%, 10%, and 20% of Co 3 O 4 are formed to evaluate the effect of decorated Co 3 O 4 weight percentage on the production of ammonia. In addition, the kinetics and the concentration of the produced ammonia are studied using these composites. Based on the comparative analysis, the 5% Co 3 O 4 /GQDs photocatalyst not only optimizes the production of ammonia related to 10% Co 3 O 4 /GQDs, and 20% Co 3 O 4 /GQDs photocatalysts but also indicates the faster kinetics of ammonia production. These results can be attributed to the more uniform distribution and the lower size of nanoparticles in 5% Co 3 O 4 /GQDs photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we report the preparation of Co3O4 nanoparticles anchored on the surface of selectively oxidized graphene flakes with KMnO4 and O3 ‐ Co3O4@GF_KMnO4 and Co3O4@GF_O3 nanocomposites ‐ and the study of their electrocatalytic performance towards the oxygen reduction (ORR) and oxygen evolution reactions (OER). Both nanocomposites displayed ORR and OER electrocatalytic activity in alkaline medium. For ORR, onset potentials of 0.79 V and 0.82 V vs. RHE were achieved for Co3O4@GF_ KMnO4 and Co3O4@GF_O3, respectively. Both nanocomposites presented excellent tolerance to methanol and, in the case of Co3O4@GF_O3, a superior long‐term stability with a current retention of 96.8% after 20 000 s. For OER, the overpotential was 0.44 and 0.45 V for Co3O4@GF_KMnO4 and Co3O4@GF_O3, respectively. Additionally, Co3O4@GF_O3 presented higher current densities, Faradaic efficiencies, and long‐term stability (current loss of 32% after 15 000 s). The superior bifunctional ORR/OER electrocatalytic activity displayed by Co3O4@GF_O3 arises from the stronger chemical coupling between Co3O4 nanoparticles and specific oxygen surface groups of GF_O3 flakes. [ABSTRACT FROM AUTHOR]

Using a hydrothermal method, a composite of Co3O4supported on graphene nanosheets (Co3O4-GNs) was prepared. Morphological characterization revealed that the Co3O4nanoparticles with a size of 100–200 nm were dispersed randomly on the planes of GNs. As an anode material for lithium-ion batteries, Co3O4-GNs composite shows an improved electrochemical performance in the initial coulombic efficiency (57%), reversible capacity (657 mAh g−1after 100 cycles at a current of 50 mA g−1) and cycling stability, which is much better than bare Co3O4and GNs electrodes. The superior results can be attributed to high surface area and good electronic conductivity of GNs. [ABSTRACT FROM PUBLISHER]