Catalyst coated diaphragms for enhanced alkaline water electrolysis
Maximilian Demnitz, Daan Wim van Kessel, Kristiaan Chpilevski, J. van der Schaaf, Matheus T. de Groot
Abstract
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.