Catalyst coated diaphragms for enhanced alkaline water electrolysis

To improve alkaline water electrolysis, catalyst coated diaphragms are prepared on Zirfon UTP 500 using polyvinylalcohol as a binder and Raney Ni and Pt (20% Pt/C; nanoparticular Pt) as catalysts to enhance the hydrogen evolution reaction. The catalyst coated diaphragms are tested under close to industrial conditions to assess their electrochemical performance and stability (60+ h). Raney Ni loaded diaphragms show 200 mV cell potential reduction at low temperature, and 150 mV at high temperature throughout the entire current density range. Nanoparticulate Pt and Pt/C loaded diaphragms perform well at low current densities (<30 mA/cm 2 ), where a overpotential reduction of 150 mV is attained. At higher current densities (>30 mA/cm 2 ) the reduction is smaller at only 50–100 mV throughout the entire temperature range, caused by an increase in Tafel slope. Long-term measurements and SEM/EDX show that the catalyst layers become unstable after several hours of experiments. • Pt and Raney Ni coated diaphragms with PVA tested were under industrial conditions. • Flow cell measurements showed cell potential improvement of 100–150 mV. • Tafel slope for Pt in 27 wt% KOH small at low currents and large at high currents. • Raney Ni performed excellent throughout all temperature and current ranges. • Stability tests of up to 60 h were conducted.