Effects of Phosphoric Acid Concentration on Platinum Catalyst and Phosphoric Acid Hydrogen Pump Performance

This work involves the study of the operational performance of phosphoric acid based electrochemical hydrogen pumps with a polybenzimidazole (PBI) electrolytic membrane. During characterization of the device, the power consumption was found to be highly sensitive to the water vapor pressure in the supply gas stream which affects the phosphoric acid concentration. The power requirement was 30 times higher when the supply gas stream was not humidified than when the supply gas stream was humidified to a dew point of 60 degrees C. The increase in power consumption was caused by a decrease in platinum catalyst activity due to the adsorption of a species on the platinum catalyst when the phosphoric acid concentration exceeded 72.4 wt% P2O5 (100 wt% H3PO4). The increase in power consumption can be prevented by humidifying the supply gas stream.