Abstract:We report the electrochemical oxidation of ferricyanide, [FeIII(CN)6]3− and characterised the oxidation product by in-situ FTIR and XAS spectroelectrochemistry methods. Oxidation of [FeIII(CN)6]3− is proposed to proceed via a tentative Fe(IV) intermediate that undergoes reduction elimination to give cis-[FeIII(CN)4(CH3CN)2]1− as stable product in acetonitrile. Speciation of the oxidation product by DFT calculations is underpinned by good agreement to experimental data.
“…During the cathodic sweep or reverse scan, ferricyanide reduction started and reverted to ferrocyanide by accepting one electron. This continuous process shows that the ferricyanide/ ferrocyanide redox reaction is a single electron transfer process 71 , 72 . Figure 8 ( A ) Cyclic voltammetric curves taken for Bare GC, rGO, Mn 3 O 4 , and Mn 3 O 4 @RGO nanocomposite with different wt% of GO (5%, 10%, and 15%) modified GCE in 1 mM K 3 [Fe(CN)6] as analyte in 0.1 M KCl electrolyte at a scan rate of 50 mVs −1 , ( B ) the EIS studies are taken into the exact solution for bare GCE and Mn 3 O 4 , (C) rGO and Mn 3 O 4 @rGO-10% nanocomposite modified GCE.…”
Section: Resultsmentioning
confidence: 94%
“…During the cathodic sweep or reverse scan, ferricyanide reduction started and reverted to ferrocyanide by accepting one electron. This continuous process shows that the ferricyanide/ ferrocyanide redox reaction is a single electron transfer process 71,72 .…”
Mn3O4 nanograins incorporated into reduced graphene oxide as a nanocomposite electrocatalyst have been synthesized via one-step, facile, and single-pot microwave-assisted hydrothermal technique. The nanocomposites were employed as cathode material of fuel cells for oxygen reduction reaction (ORR). The synthesized product was thoroughly studied by using important characterization, such as XRD for the structure analysis and FESEM and TEM analyses to assess the morphological structures of the material. Raman spectra were employed to study the GO, rGO bands and formation of Mn3O4@rGO nanocomposite. FTIR and UV–Vis spectroscopic analysis were used to verify the effective synthesis of the desired electrocatalyst. The Mn3O4@rGO-10% nanocomposite with 10 wt% of graphene oxide was used to alter the shiny surface of the working electrode and applied for ORR in O2 purged 0.5 M KOH electrolyte solution. The Mn3O4@rGO-10% nanocomposite electrocatalyst exhibited outstanding performance with an improved current of − 0.738 mA/cm2 and shifted overpotential values of − 0.345 V when compared to other controlled electrodes, including the conventionally used Pt/C catalyst generally used for ORR activity. The tolerance of Mn3O4@rGO-10% nanocomposite was tested by injecting a higher concentration of methanol, i.e., 0.5 M, and found unsusceptible by methanol crossover. The stability test of the synthesized electrocatalyst after 3000 s was also considered, and it demonstrated excellent current retention of 98% compared to commercially available Pt/C electrocatalyst. The synthesized nanocomposite material could be regarded as an effective and Pt-free electrocatalyst for practical ORR that meets the requirement of low cost, facile fabrication, and adequate stability.
“…During the cathodic sweep or reverse scan, ferricyanide reduction started and reverted to ferrocyanide by accepting one electron. This continuous process shows that the ferricyanide/ ferrocyanide redox reaction is a single electron transfer process 71 , 72 . Figure 8 ( A ) Cyclic voltammetric curves taken for Bare GC, rGO, Mn 3 O 4 , and Mn 3 O 4 @RGO nanocomposite with different wt% of GO (5%, 10%, and 15%) modified GCE in 1 mM K 3 [Fe(CN)6] as analyte in 0.1 M KCl electrolyte at a scan rate of 50 mVs −1 , ( B ) the EIS studies are taken into the exact solution for bare GCE and Mn 3 O 4 , (C) rGO and Mn 3 O 4 @rGO-10% nanocomposite modified GCE.…”
Section: Resultsmentioning
confidence: 94%
“…During the cathodic sweep or reverse scan, ferricyanide reduction started and reverted to ferrocyanide by accepting one electron. This continuous process shows that the ferricyanide/ ferrocyanide redox reaction is a single electron transfer process 71,72 .…”
Mn3O4 nanograins incorporated into reduced graphene oxide as a nanocomposite electrocatalyst have been synthesized via one-step, facile, and single-pot microwave-assisted hydrothermal technique. The nanocomposites were employed as cathode material of fuel cells for oxygen reduction reaction (ORR). The synthesized product was thoroughly studied by using important characterization, such as XRD for the structure analysis and FESEM and TEM analyses to assess the morphological structures of the material. Raman spectra were employed to study the GO, rGO bands and formation of Mn3O4@rGO nanocomposite. FTIR and UV–Vis spectroscopic analysis were used to verify the effective synthesis of the desired electrocatalyst. The Mn3O4@rGO-10% nanocomposite with 10 wt% of graphene oxide was used to alter the shiny surface of the working electrode and applied for ORR in O2 purged 0.5 M KOH electrolyte solution. The Mn3O4@rGO-10% nanocomposite electrocatalyst exhibited outstanding performance with an improved current of − 0.738 mA/cm2 and shifted overpotential values of − 0.345 V when compared to other controlled electrodes, including the conventionally used Pt/C catalyst generally used for ORR activity. The tolerance of Mn3O4@rGO-10% nanocomposite was tested by injecting a higher concentration of methanol, i.e., 0.5 M, and found unsusceptible by methanol crossover. The stability test of the synthesized electrocatalyst after 3000 s was also considered, and it demonstrated excellent current retention of 98% compared to commercially available Pt/C electrocatalyst. The synthesized nanocomposite material could be regarded as an effective and Pt-free electrocatalyst for practical ORR that meets the requirement of low cost, facile fabrication, and adequate stability.
“…The electron-withdrawing ability of −NO 2 makes its interaction energy smaller than those of most metal ions, which gives rise to a labile nitroprusside. Meanwhile, it is difficult for O 2 to free CN – single-handedly because CNO – /[Fe(CN) 6 ] 4– has a relatively positive SEP, greater than +1.16 V vs the normal hydrogen electrode (NHE), − which makes it difficult to be oxidized by O 2 /H 2 O (+1.229 V vs NHE). The introduction of Cu 2+ /Cu + (+0.17 V vs NHE) will reduce the SEP of the complexed cyanide by competitive binding, and this process results in it being more easily oxidized by oxidants.…”
The secondary effluent of coking wastewater treatment plants often contains a low content but tenacious cyanides. In this study, a full-scale double physicochemical synergistic OHHO process was used to investigate the distribution of various cyanides in each unit. The cyanides tend to dissolve and be released under aerobic conditions and precipitated or be adsorbed under anaerobic/hydrolytic conditions. The toxicity and biochemical stability of cyanide conjugates bring about functional control of ammonification−nitritation−nitrification as total cyanides (TCNs) increase under polymetallic restriction. Polymetallic competitive inhibition and π bond activation between coexisting ligands (OH − , Cl − , NH 3 , and anionic dissolved organic matter (DOM)) and metal ions allowed us to maintain the balance between ionization and complexation of CN − . This paper explored the biological function and migration behavior of cyanide as an indicator in wastewater and water environments and proposed a feasible cyanide removal strategy via polymetallic competition. The synergy between competitive inhibition and activation owing to the coexistence of diverse ligands may benefit the stable occurrence of cyanides in the natural water environment, which is crucial for understanding the geochemical balance and cycle of characteristic pollutants.
“…Solution-phase HCF is a centrosymmetric molecule, and when adsorbed onto the nanorod surface, the symmetry changes and new peaks appear. 57 The interaction with the surface also leads to the broadening of the infrared peaks. The adsorption of HCF is further corroborated with the EDX spectra, thus showing Fe adsorption after HCF treatment (Figure 4F).…”
Section: ■ Results and Discussionmentioning
confidence: 99%
“…Solution-phase HCF is a centrosymmetric molecule, and when adsorbed onto the nanorod surface, the symmetry changes and new peaks appear . The interaction with the surface also leads to the broadening of the infrared peaks.…”
Plasmonic gold nanorods (AuNRs) are often employed as photoacoustic (PA) contrast agents due to their ease of synthesis, functionalization, and biocompatibility. These materials can produce activatable signals in response to a change in optical absorbance intensity or absorbance wavelength. Here, we report a surprising finding: Ag 2 S/Se-coated AuNRs have a ∼40-fold PA enhancement upon addition of an oxidant but with no change in absorption spectra. We then study the mechanism underlying this enhancement. Electron micrographs and absorption spectra show good colloidal stability and retention of the core−shell structure after potassium hexacyanoferrate(III) (HCF) addition, ruling out aggregation and morphology-induced PA enhancement. X-ray diffraction data showed no changes, ruling out crystallographic phase changes upon HCF addition, thus leading to induced PA enhancement. Attenuated total reflectance−Fourier transform infrared spectroscopy and zeta potential analysis suggest that PA enhancement is driven by the irreversible displacement of hexadecyltrimethylammonium bromide with HCF. This is further confirmed using elemental mapping with energy-dispersive X-ray analysis. PA characterization after HCF addition showed a four-fold increase in the Gruneisen parameter (Γ), thus resulting in PA enhancement. The PA enhancement is not seen in uncoated AuNRs or spherical particles. Two possible mechanisms for PA enhancement are proposed: first, the photo-induced redox heating at the Ag 2 S/Se shell−HCF interface, resulting in an increase in temperature-dependent Γ, and second, an enhanced electrostriction response due to HCF adsorption on a layered plasmonic nanoparticle surface, resulting in a high thermal expansion coefficient (β) that is directly proportional to Γ.
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