Abstract
Keeping global warming at 2 degrees and below as stated in the "Paris Climate Agreement" and minimizing emissions can only be achieved by establishing a hydrogen (H(2)) ecosystem. Therefore, H(2) technologies stand out in terms of accomplishing zero net emissions. Although H(2) is the most abundant element in the known universe, molecular H(2) is very rare in nature and must be produced. In H(2) production, reforming natural gas and renewable hydrogen processes using electrolyzers comes to the fore. The key to all these technologies is to enhance production speed, performance, and system lifetime. At this point, composite membranes used in both processes come to the fore. This review article summarizes composite membrane technologies used in methane, ethanol, and biomass steam reforming processes, proton exchange membranes, alkaline water electrolysis, and hybrid sulfur cycle. In addition to these common H(2) production technologies at large quantities, the innovative systems developed with solar energy integration for H(2) generation were linked to composite membrane utilization. This study aimed to draw attention to the importance of composite membranes in H(2) production. It aims to prepare a guiding summary for those working on membranes by combining the latest and cutting-edge studies on this subject.