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Role of RGO and RGO-Pt as an attractive electrocatalyst for efficient electrochemical reduction of U(VI) in HNO3
Kuntal Kumar Pal1,2, Chanchal Ghosh3, Ramnathaswamy Pandian4
1Reprocessing Material Development Section, Reprocessing Group, Indira Gandhi Centre for Atomic Research, 603102, Kalpakkam, India. kuntal@igcar.gov.in.
Abstract:
Electrochemical reduction of U(VI) to U(IV) in nitric acid-hydrazine medium is the key process step to successfully achieve the partitioning of Pu from U in the Plutonium Uranium Reduction Extraction (PUREX) process, adopted worldwide in the spent nuclear fuel reprocessing plants. The present method for the electrochemical reduction of U(VI) to U(IV) is not viable for the large-scale production of U(VI) to U(IV) due to its several drawbacks, including very high overpotential and associated hydrogen evolution reaction. In this report, we have shown that the RGO and RGO-Pt could be an attractive electrocatalyst material for the efficient production of U(IV) from U(VI) in HNO3-N2H4 medium with a significantly lower overpotential and greater selectivity. The linear sweep voltammetry (LSV) plots and corresponding Tafel slope analysis have shown that the U reduction over RGO and RGO-Pt takes a completely different pathway as compared to the reduction over Pt and Ti, which is used in commercial plants. Moreover, the cyclic voltametric and electrochemical impedance spectroscopy studies have shown that the hydrogen evolution reaction has also been greatly suppressed over the RGO as compared to the RGO-Pt and Pt rod, thus would improve the faradic efficiency for the U(VI) to U(IV) conversion reaction at higher overpotential.
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