Hi Tali,
I see that you are looking for a PEM electrolyser block in the Simulink Library browser. However, please note that Simulink does not include a built-in PEM (Proton Exchange Membrane) electrolyzer block in its standard library. You can nevertheless achieve the same by modelling it and them using the corresponding model as a subsystem in your original project.
Please refer to the following documentation about modelling PEM : https://www.mathworks.com/help/simscape/ug/pem-electrolysis-system.html
Hope this helps
