Effect of Carbon Substrate Pretreatment on the Ecsa and Activity of RhxSy/C Catalyst

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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 can be used 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 catalyst 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. By literatures3,4, smaller particle size can be achieved if more preferable surface for precipitation of Rh cation is provided. Figure 1 shows the mass specific active surface area (ECSA) of the catalyst with pretreated carbon and commercial RhxSy catalysts. It shows that the RhxSy catalyst with pretreated carbon material has much higher mass specific ECSA than commercial RhxSy. This presentation will discuss the approach used to synthesis the RhxSy catalyst with pretreated carbon and the characteristics and performance of this catalyst. Figure 1. CV of catalyst with pretreated carbon and commercial one , measured in 1M H2SO4 with 10 mV/s scan rate