Core-Shell Rhodium Sulfide As Catalyst for HER/HOR in HBr Solution
Authors: Li Yuanchao , Nguyen Trung Van 
Published: February 2020

Electrical energy storage technologies are needed when significant fraction of intermittent renewable energy sources such as wind and solar are integrated into the electrical grids. The hydrogen-bromine (H2-Br2) reversible fuel cell system is one of the promising technologies because of its high round-trip conversion efficiency, high power density capability and low cost. In a hydrogen bromine fuel cell, while carbon surface can be for the bromine reactions, a noble metal such as platinum is needed for the hydrogen reactions. Since platinum is not stable in HBr/Br2 environment and HBr and Br2 are expected to cross from the bromine electrode to the hydrogen electrode during operation, a more durable and active catalysts is needed for the hydrogen reactions. RhxSy catalysts have been found to be stable in the HBr/Br2 environment and as active as platinum per active area.1, 2

Commercial RhxSy catalysts have large and broad particle sizes (12-40 nm) and consequently low mass specific active area (< 10 m2/g) for HOR. To address this problem, we explore the core-shell approach used by others 3 as a way to increase the mass specific area of these RhxSy catalysts. Figure 1 shows the mass specific active surface area (ECSA) of the core-shell and commercial RhxSy catalysts, and Table 1 shows a comparison of the mass specific ECSA and durability of commercial 20 wt. % Pt/C and commercial and core-shell RhxSy catalysts. These results show that the core shell RhxSy catalyst has much higher mass specific ECSA than commercial RhxSy catalyst and superior durability over platinum catalyst. This presentation will discuss the approach used to synthesis the core-shell RhxSy catalyst and the characteristics and performance of this catalyst.

Figure 1. CV of core-shell and commercial RhxSy catalysts, measured in 1M H2SO4 at 10mV/s

KU Core-Shell RhxSy/C

20 wt.% Pt/C

Commercial RhxSy/C

Time in 1M HBr (hr)

m2/g
%
m2/g
%
m2/g
%

0
61.4
100
127.3
100
7.8
100

24
60.2
98
82.7
65

48
58.4
97
42.2
51

Table 1.
Durability in 1M HBr solution of Pt/C and commercial and core-shell RhxSy catalysts

References

Anna Ivanovskaya, Nirala Singh, Ru-Fen Liu, Haley Kreutzer, Jonas Baltrusaitis, Trung Van Nguyen, Horia Metiu, Eric W McFarland, “Transition Metal Sulfide Hydrogen Evolution Catalysts for Hydrobromic Acid Electrolysis,” Langmuir, 29(1), 480-492 (2013).

Jahangir Masud, Trung Van Nguyen, Nirala Singh, Eric McFarland, Myles Ikenberry, Keith Hohn, Chun-Jern Pan, and Bing-Joe Hwang, “A RhxSy/C Catalyst for the Hydrogen Oxidation and Hydrogen Evolution Reactions in HBr,” J. Electrochem. Soc., 162 (4), F455-F462 (2015).

Hee-Young Park, Tae-Yeol Jeon, Jong Hyun Jang, Sung Jong Yoo, Kug-Seung Lee, Yoon-Hwan Cho, Kwang-Hyun Choi, Yong-Hun Cho, Namgee Jung, Young-Hoon Chung and Yung-Eun Sunga, “Hydrogen Oxidation Reaction Activity of Sub-Monolayer Pt-Shell/Pd-Core Nanoparticles,” J. Electrochem. Soc., 160 (1), H62-H66 (2013).

Acknowledgements

The work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000262 and the National Science Foundation under Grant No. EFRI-1038234 and No. 1416874, as a sub-award from Proton Onsite.

Figure 1