Improved polymer electrolyte membrane water electrolyzer performance by using carbon black as a pore former in the anode catalyst layer

Abstract

The porosity of anode polymer electrolyte membrane water electrolyzer catalyst layers (CLs) is usually low due to the use of an unsupported catalyst. By adding carbon to the Ir catalyst ink, which is then oxidized in-situ, the CL porosity can be increased from 58% to 77% while the number of CL cracks is decreased. The electrochemical surface area (ECSA) also increases from 21.5 to 28.3 m2/g. Cell performance improves substantially for cells with carbon at both low and high current densities. At 1.8 V, the current density increases from 3.16 to 3.70 A/cm2 with increasing carbon content. Volcano-shaped cracks, observed in used CL without carbon, disappear with the addition of carbon. These cracks are hypothesized to be caused by high gas pressures within the CL, which are reduced due to improved mass transport. The degradation rate also improves from 626 to 522 μV/h with carbon addition. Anode electrodes with and without carbon are also fabricated with a low electrically conductive IrOx catalyst. Results also show increased porosity, ECSA, and performance at low current density, however no improvement was observed at high current density.