The rapid expansion of renewable energy sources presents a great challenge to balance the electric grid due to their intermittent and volatile nature. The excess power can be converted into a gaseous energy carrier, hydrogen via Power-to-Gas technology. Alkaline water electrolysis can be operated in a dynamic mode using renewable energy sources on a large scale. However, the risk of gas crossover across a porous separator rapidly increases when the electrolyzer operates at a low partial load or at high pressure, leading to efficiency loss and a safety issue. Herein, we report the development of alkaline electrolyzer separator with high hydroxide conductivity and reduced gas crossover. This result will help alkaline electrolyzer systems be operated as more controllable loads.