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Electrochemical investigation of urea oxidation reaction on β Ni(OH)2 and Ni/Ni(OH)2.
- Source :
-
Electrochimica Acta . Jul2018, Vol. 278, p405-411. 7p. - Publication Year :
- 2018
-
Abstract
- Urea oxidation is the key limiting reaction in energy conversion devices based on this molecule. Ni-based catalysts are widely used to catalyze this reaction via the intermediate formation of reactive NiOOH from nickel hydroxide. In this study, β Ni(OH) 2 urea oxidation activity is compared to that of Ni/Ni(OH) 2 . Electrochemical active surface area, exchange current density, rate constant, and capacitance are estimated for these catalysts to mechanistically probe the reaction. A quantitative electrochemical analysis of urea oxidation on these catalyst surfaces yields important reaction parameters. The reaction orders of β Ni(OH) 2 with respect to KOH and (NH 2 ) 2 CO are 1.22 and 0.26, respectively, at a kinetically-controlled potential of 1.43 V vs. RHE. The reaction order with respect to KOH decreases gradually with potential and it is almost constant with urea. The similar trends in reaction order are observed with Ni/Ni(OH) 2 . Electrochemical impedance measurements displayed lower charge-transfer resistance of β Ni(OH) 2 indicative of faster urea oxidation kinetics. It is observed that at the potential of 1.43 V, the charge transfer resistance of β Ni(OH) 2 (87.3 Ω cm ECSA 2 ) lowered by a factor of ∼1.23 compared to Ni/Ni(OH) 2 (107.6 Ω cm ECSA 2 ). The electrochemical surface area normalized heterogeneous rate constant of β Ni(OH) 2 is ∼2 times higher than that of Ni/Ni(OH) 2 , in line their high intrinsic urea oxidation activity, capacitance and higher electrochemical phase stability. Moreover, the electrochemical chemical mechanism is observed on both catalysts in support with earlier report [ 1 ]. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00134686
- Volume :
- 278
- Database :
- Academic Search Index
- Journal :
- Electrochimica Acta
- Publication Type :
- Academic Journal
- Accession number :
- 129847129
- Full Text :
- https://doi.org/10.1016/j.electacta.2018.05.049