High Hydrogen Evolution Reaction (HER) and Hydrogen Oxidation Reaction (HOR) Activity Rh x S y Catalyst Synthesized with Na 2 S for Hydrogen-Bromine Fuel Cell

Yuanchao Li and Trung Van Nguyen
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Yuanchao Li: Chemical and Petroleum Engineering Department of University of Kansas, University of Kansas, Lawrence, KS 66045, USA
Trung Van Nguyen: Chemical and Petroleum Engineering Department of University of Kansas, University of Kansas, Lawrence, KS 66045, USA

Energies, 2020, vol. 13, issue 15, 1-17

Abstract: A Rh x S y /C catalyst with high mass-specific electrochemical surface area (ECSA/mass), high hydrogen oxidation reaction (HOR)/hydrogen evolution reaction (HER) activity, and high Nafion ® ionomer-affinity was synthesized and evaluated. A new sulfur source, Na 2 S instead of (NH 4 ) 2 S 2 O 3 , was applied to prepare the rhodium sulfide precursor Rh 2 S 3 that resulted in a Rh x S y catalyst with higher HOR/HER catalytic activity after thermal treatment. The higher activity was attributed to the higher quantity formation of the more active phase Rh 3 S 4, in addition to the other active Rh 17 S 15 phase, in the Rh x S y catalyst. Using this new sulfur source, carbon substrate functionalization, and the mass-transfer-controlled nanoparticle growth process, the average particle size of this catalyst was reduced from 13.5 nm to 3.2 nm, and its ECSA/mass was increased from 9.3 m 2 /g-Rh to 43.0 m 2 /g-Rh. Finally, by applying the Baeyer–Villiger and ester hydrolysis process to convert the Nafion ® ionomer-unfriendly ketone group on the carbon support surface to the Nafion ionomer-friendly carboxylic group, which increases the Nafion ® affinity of this catalyst, its use in the hydrogen electrode of an H 2 -Br 2 fuel cell resulted in a performance that is 2.5× higher than that of the fuel cell with a commercial Rh x S y catalyst.

Keywords: hydrogen-bromine fuel cell; rhodium sulfide catalyst; hydrogen evolution; hydrogen oxidation catalyst (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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