H2+CO32- →CO2+H2O+2e (1)
H2+CO32- →2HCO3-+2e (2)
However, testing under single cell conditions using a commercially available AEM (Tokuyama Corp., Japan, A201 membrane), we discovered that feeding the anode side (OER side) with 1% K2CO3 resulted in a decreased cell voltage by up to 400 mV, compared to the traditional DI water feed. Under this new feeding condition, the cell voltage was below 2 V at current densities in excess of 200 mA/cm2. Moreover, this performance was found to be stable for prolonged operation over several hundred hours. This test, conducted by our validation partner Proton On-Site (Wallingford, CT), is in variance to conventional thinking on the negative effect of carbonate formation. We believe that feeding 1% carbonate in the anode side does not interfere with the OER mechanism but further improves the conductivity of the AEMs system.
In this study, half-cell analysis using OER and HER catalysts (PGM vs. non-PGM) was conducted, and full cell data was obtained. This presentation will provide detailed interfacial perspectives by four studies. The first study will comprise of an RDE experiment using various electrolytes containing KOH, K2CO3 and mixtures thereof. The second study will be conducted using a unique solid-state cell design to understand catalyst, ionomer and membrane interfaces. The third study will be done using a micro-electrode to combine simultaneous mass transport and kinetics at the membrane interface. The final study will compare the solid cell, or full water splitting cell using an A-201 membrane, vs. a liquid cell (H2 pump and O2pump) or half-cell using conducting carbonate/hydroxide electrolyte chamber attached to Hg/HgO reference.