Two
hybrid electrocatalysts formulated as Rh/RhO
x
-Ni(OH)2-rGO and Rh/RhO
x
-Ni(OH)2-Y/rGO were synthesized using zeolite-Y and reduced
graphene oxide (rGO) as solid support and hard templating agents.
The hybrid composites served as effective electrocatalysts for the
electrochemical oxidation of both methanol and ethanol. X-ray photoelectron
spectroscopic analysis predicted for the creation of metallic rhodium,
Rh(0), sites that helped in reducing the CO poisoning during electrocatalytic
decomposition of the C1 and C2 alcohols. The zeolite-Y-embedded electrocatalyst,
Rh/RhO
x
-Ni(OH)2-Y/rGO, showed
high CO tolerance in comparison to Rh/RhO
x
-Ni(OH)2-rGO and Pt/C. This was further evident from the
CO stripping experiment. The zeolite-Y matrix was found to have significant
impact in enhancing the current density and durability of the electrocatalysts
in both methanol and ethanol oxidation reaction (MOR and EOR) by stabilizing
the low valent Rh species. The maximum current density in the case
of MOR was found to be 5.6 A/mg, while that in the case of EOR was
found to be 7.1 A/mg. The zeolite-Y-supported electrocatalyst exhibited
stability up to 1000 cycles, which was retained for 13.8 h during
MOR/EOR without any significant loss in the current density. The creation
of mesoporous channels in zeolite-Y after its post-modification helped
in high mass transfer and allowed to follow a diffusion-controlled
mechanism. The linear relationship between current density and the
square root of the scan rate also suggested a diffusion-controlled
process. The catalysts also exhibited good methanol and ethanol tolerance
with the maximum concentration up to 4 and 3 M, respectively.
The influence of two different surface matrices, that is, zeolite‐Y and multi‐walled carbon nanotubes (MWCNTs), on the electrocatalytic ability of Ni(OH)2 combined with MnO2 has been studied. The Ni and Mn loaded in different ratio exhibited different current density with respect to the change in the nature of support. The MnO2−Ni(OH)2 catalyst decorated like a fish in a net‐stock at the interface of the zeolite‐Y and the MWCNT with high Ni(II) content provided the highest current density of 3.8 Amg−1 and 3.6 Amg−1 with platinum and graphitic rod as counter electrode, respectively. The study revealed that both the concentration of the Ni(II) as well as the nature of the support influenced the electrochemical behaviour of MnO2−Ni(OH)2. The electrochemical surface area as well as the durability of the catalyst having two different supports showed higher values in comparison to those in single matrix. The plot of current density vs. square root of scan rate showed diffusion control methanol oxidation process. The results predicted that the MnO2−Ni(OH)2 catalyst containing both zeolite‐Y and MWCNT surface indicated that under the highly basic condition it can withstand for long period without significant loss in current density during the methanol oxidation reaction process.
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