The scientists examined how to make hydrogen without pollution by using wind or solar power to make electricity and then split water into hydrogen, creating what's known as "green hydrogen." Water electrolysis is a crucial way to make hydrogen emission-free. They studied two methods, alkaline water electrolysis and proton exchange membrane water electrolysis, analyzing their technical details and development stages. In the future, water electrolysis could become the main way to produce hydrogen. The researchers suggested key directions for improving both alkaline and proton exchange membrane water electrolysis techniques.