The effect of concentration polarization and chemical interactions on electrochemical hydrogen pump

Electrochemical hydrogen pump is expected to play an important role in, e.g., H2 extraction from natural gas pipelines, by-product hydrogen purification. The influence of typical concomitant CH4 and CO2 on electro-chemical hydrogen pump is systematically investigated in this study over a wide range of gas content (CH4 or CO2: 10-80 %) and temperature (26-60 degrees C), with the focus on two main inhibition effects, i.e., concentration polarization and chemical interaction. An Faradaic efficiency of 86-96 %, i.e., below 100 %, is obtained as to the H2/CH4 mixture separation due to concentration polarization effect, which is even lower in case of H2/CO2, due to additional chemical interactions between CO2 and Pt anode catalysts. The inhibition of concentration po-larization is more significant than that of chemical interactions, and the former can be suppressed by increasing the operating temperature and pressure due to enhance catalytic activity and proton conductivity. As to these two gas mixtures, the energy consumption ranged from 0.2 to 2.0 kWh/m3 with the increase of applied current from 125 to 1250 mA. The electrochemical pump exhibits limited H2 purity of 98.6 %-99.7 % due to the existence of nafion membrane defects, which requires to be further improved.