Pt-Co3O4 Superstructures by One-Pot Reduction/Precipitation in Bicontinuous Microemulsion for Electrocatalytic Oxygen Evolution Reaction

Abstract

Bicontinuous microemulsions (BCME) were used to synthesize hierarchical superstructures (HSs) of Pt-Co3O4 by reduction/precipitation. BCMEs possess water and oil nanochannels, and therefore, both hydrophilic and lipophilic precursors can be used. Thus, PtAq-CoAq, PtAq-CoOi, PtOi-CoAq and PtOi-CoOi were prepared (where Aq and Oi stand for the precursor present in aqueous or oily phase, respectively). The characterization of the Pt-Co3O4-HS confirmed the formation of metallic Pt and Co3O4 whose composition and morphology are controlled by the initial pH and precursor combination, determining the presence of the reducing/precipitant species in the reaction media. The electrocatalytic activity of the Pt-Co3O4-HSs for oxygen evolution reaction (OER) was investigated using linear sweep voltammetry in 0.1 M KOH and compared with Pt-HS. The lowest onset overpotentials for Pt-Co3O4-Hs were achieved with PtOi-CoOi (1.46 V vs. RHE), while the lowest overpotential at a current density of 10 mA cm−2 (η10) was obtained for the PtAq-CoAq (381 mV). Tafel slopes were 102, 89, 157 and 92 mV dec−1, for PtAq-CoAq, PtAq-CoOi, PtOi-CoAq and PtOi-CoOi, respectively. The Pt-Co3O4-HSs showed a better performance than Pt-HS. Our work shows that the properties and performance of metal–metal oxide HSs obtained in BCMEs depend on the phases in which the precursors are present.

Dopamine‐Assisted Coral Films of Cobalt as Bifunctional Electrodes for Overall Water Splitting

“…The small oxidation peak for S1 and S2 is at 1.1 V (vs. RHE) and 1.09 V (vs. RHE), respectively, which corresponds to conversion from Co 2+ to Co 3+ state. [ 26 ] As conversion of Co 2+ /Co 3+ is involved, more active Co sites are accessible to the catalysis process. [ 27 ] It is evident from literature that the peak between 1.07 and 1.1 V is associated with conversion of Co 2+ to Co 3+ oxidation; further, Co 3+ can be considered as an active site for OER.…”

“…This peak prior to OER turn‐on is due to the oxidative formation of Co 2+ and Co 3+ active sites. [ 26 ] The absence of this in case of Ni−dopamine−Co electrodes indicates that the dopamine monolayer coverage probably prohibits the electrochemical oxidation of nickel. There is a slight increase in current density with dopamine modification.…”

Usage of Platinum Nanoparticles for Anticancer Therapy over Last Decade: A Review

“…The chemical method should also avoid aggregation of nanoparticles. Different chemical methods such as wet chemical reduction, [68] electrochemical process, [69] photochemical reduction, [70] microemulsion, [71] co-precipitation, [72] sono-decomposition, [73] thermal decomposition, [74] and chemical vapor deposition [75] are methods use to synthesize PtNPs.…”

Biomimetic Hierarchical Superstructures: Approaches Using Bicontinuous Microemulsions and Electrodeposition

“…This is of great interest because their performance often exceeds the properties associated with their monometallic counterparts; that is, the physicochemical properties of bimetallic nanomaterials are often better than those of their monometallic counterparts, which is commonly explained as synergistic effects (Notar Francesco et al, 2014). For example, by testing the same microemulsion system as described for platinum in the previous example, the synthesis of a hybrid metal-metal oxide superstructure of Pt-Co 3 O 4 was carried out (Adesuji et al, 2020a) As mentioned above, certain properties can be improved when nanoscale building blocks self-assemble into HSS. An example is the formation of self-assembled silver plasmonic nanoparticles, as shown in Figure 7.…”

“…Hierarchical superstructures (HSS) are nanometric building blocks that self-assemble to extend into one or more dimensions, with a constant and reproducible architectural design. Arrangement of nanoparticles into higher-order domains allows tuning their magnetic, optical, catalytic, or electronic responses by coupling the properties of individual building blocks (Adesuji et al, 2020a;2020b).…”