Development of cost-effective porous transport layers (PTLs) for polymer electrolyte membrane (PEM) electrolyzers is crucial for the implementation of clean energy systems. In this thesis, novel PTLs with through pores have been investigated. Limited mass transport in the in-plane direction was observed in through pore PTLs, using in operando synchrotron X-ray radiograph. Furthermore, the limited in-plane mass transport led to dehydration of the catalyst layer (CL). Therefore, the placement of through pores play a critical role in the performance of PEM electrolyzers. Next, through pore PTLs consisting of woven meshes were studied. The contact resistance between the woven mesh PTL and the CL dominated performance losses, and smaller pore sizes improved the contact resistance. Stacking meshes with different pore sizes resulted in inhomogeneous compression of the CL, significantly degrading the PEM electrolyzer performance. The results from this thesis contribute to the development of cost-effective PTLs for next generation PEM electrolyzers.