Development of partially hydrophobic surfaces to enhance the efficiency and durability of electrodes for alkaline water electrolysis

• Development of catalytic coatings by codeposition of PTFE and Ni catalyst using a scalable method • Low surface free energy of the electrodes was achieved by PTFE incorporation • Fast growth and bubble release were promoted by the hydrophobic electrode surface • Significant fall of HER and OER overpotentials were achieved by hydrophobic electrodes • High energy efficiency of water splitting was achieved by whole-cell operating with hydrophobic electrodes Hydrogen gas is a fuel with a reduced environmental impact, and its production is currently promoted by water electrolysis. However, the growth and release of bubbles on the surface of electrodes involved in hydrogen and oxygen evolution reactions (HER and OER) affect the overpotential of the electrolysis process. Therefore, the study of gas bubble behavior and management has become a crucial aspect to consider when seeking to improve energy efficiency in the water-splitting process. This work shows that integrating porous electrodes partially coated with hydrophobic material (PTFE) reduces overpotentials for both HER and OER, showing excellent catalytic activities in stationary tests. Physical characterization of electrodes indicates that the PTFE particles are distributed as nodules, providing a larger electrochemical surface area with low surface free energy. At a current density of 400 mA cm -2 , the PTFE-modified electrodes exhibit overpotentials of 193 mV for HER and 230 mV for OER, compared to 230 mV and 278 mV, respectively, for the electrodes without PTFE. Furthermore, the full cell assembled with PTFE-modified electrodes achieves a low operating voltage of 1.60 V at 400 mA cm -2