rGO/PEDOT:PSS/NiMn₂O₄ Nanohybrid: An Inexpensive Anode Catalyst for Methanol and Ethylene Glycol Electro-Oxidation

Abstract

Present work reports the development of a mesoporous ternary nanohybrid (GPN) based on NiMn2O4, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and reduced graphene oxide (rGO) for methanol (MeOH) and ethylene glycol (EG) oxidation. Initially, NiMn2O4 nanoparticles have been synthesized using solvothermal-assisted calcination and then polymerization of EDOT monomer has been done in presence of rGO nanosheets and NiMn2O4 nanoparticles to form GPN nanohybrid. The current densities of 70.4 mA cm−2 at an onset potential of 0.21 V in 0.5 M MeOH and 53 mA cm−2 at an onset potential of 0.32 V in 0.5 M EG solution have been recorded at GPN modified indium tin oxide (ITO) electrode. This electrode exhibits a current retention of 87% in 0.5 M MeOH and 81% in 0.5 M EG solution after 700 cycles. The improved electrocatalytic activity and cyclic stability of GPN can be attributed to the presence of rich binary active sites of Ni and Mn species, large surface area and high electrical conductivity of rGO and uniform dispersion of NiMn2O4 nanoparticles over PEDOT:PSS. This work demonstrates the potential of GPN nanohybrid as an alternative to platinum towards MeOH and EG electro-oxidation.

Hybrid 2D‐1D nanostructure of NiO composited with PEDOT : PSS and rGO : Bifunctional electrocatalyst towards methanol oxidation and oxygen evolution reaction

“…The FTIR spectrum of NiO nanostructure (Figure S3ii) shows a strong peak at 416 cm −1 related to NiO stretching. Additionally, the peak observed at 572 cm −1 corresponds to NiOH stretching vibration 48 . Apart from NiOH vibration, two other bands observed at 3437 and 1633 cm −1 (Figure S3ii) corresponds to OH stretching vibrations and H‐O‐H bending vibrations mode, respectively.…”

“…The characteristic XRD peaks in PEDOT:PSS are seen at 17.7° and 26.2°, attributing to the interlayer distance of 5 and 3.4 Å, respectively. The small intense peak of PEDOT:PSS at 17.7° appears due to amorphous PSS chain structure and the broad peak at 26.2° arises owing to π‐π interchain stacking between (010) planes 48 . In Figure S3i, well‐defined XRD peaks of NiO are observed at 35.3°, 41.5° and 61°, signifying (111), (200) and (220) planes of NiO crystals, respectively.…”

“…The peaks at 1638, 1525, 1197 and 1065 cm −1 are assigned CC alkane stretching, CC aromatic stretching, COC stretching and CCO stretching, respectively. The signature peaks of PEDOT:PSS seen at 834, 672 and 1321 cm −1 correspond to CS stretching of thiophene ring and SO 3 H group of PSS, respectively 48,49 . The FTIR spectrum of NiO nanostructure (Figure S3ii) shows a strong peak at 416 cm −1 related to NiO stretching.…”

“…The sharp Raman band at 1432 cm −1 is assigned to C α = C β (C α is the adjacent to sulphur atom, while C β is adjacent to C α ) symmetrical stretching, while the bands at 1503 and 1560 cm −1 are attributed to C α = C β antisymmetric stretching and quinoid structure, respectively 51 . However, a small intense band around 2876 cm −1 arises owing to existence of CH stretching vibration 48 . The dominant Raman bands of rGO, D band at 1345 cm −1 represents breathing modes of carbon ring or K‐point phonons of A 1g symmetry that associated with defects present in carbon structures and G band at 1581 cm −1 is attributed to in plane stretching vibration caused by E 2g phonon mode of sp 2 bonded C atoms.…”

“…Furthermore, the existence of sulphur atoms from PEDOT and PSS is confirmed in S 2p spectrum (Figure 3E). The deconvoluted peak at 163.8 corresponds to S 2p 3/2 state, while the peak at 165 eV is assigned to S 2p 1/2 state of thiophene ring in PEDOT 48 . The peak at 168.3 eV is related to S 2p 3/2 electronic configuration of sulfonate (SO 3− ) and peak at 168.9 eV is attributed to S 2p 1/2 state of sulfonic acid groups (SO 3 H) in PSS, respectively 48 …”