A novel catalyst coated membrane embedded with Cs-substituted phosphotungstates for proton exchange membrane water electrolysis

Catalyst coated membrane (CCM) is the core component of proton exchange membrane (PEM) water electrolysis and the main place for electrochemical reaction and mass transfer. Its properties directly affect the performance of PEM water electrolysis. Aiming at decreasing the polarization loss and the ohmic loss, a novel CCM embedded with Cs1.5HPA in the skeleton of the Nafion® ionomer and the Nafion® membrane was prepared and possessed functionality of improved protonic conductivity. Meanwhile, the Cs1.5HPA-Nafion ionomer content in the catalyst layers was further optimized. The SEM, EDS and pore volume distribution measurement showed that the Cs1.5HPA embedded in the CCM without agglomeration and the micropore and mesopore were well distributed in the catalyst layer. Furthermore, CCMs were tested in a PEM water electrolyser at 80 °C, beneficial effects on both the Tafel slope and the iR loss were obtained due to the improved protonic conductivity as well as the appropriate pore structure and increased specific pore volume. The performance of the electrolyser cell was obviously improved with the novel CCM. The highest cell performance of 1.59 V at 2 A cm−2 was achieved at 80 °C. At 35 °C and 300 mA cm−2, the cell showed good durability within the test period of up to 570 h.