This review discusses recent advancements in vapor-fed photoelectrochemical (PEC) systems for hydrogen production using water vapor as a hydrogen resource. The PEC system employs a proton exchange membrane (PEM) as a solid polymer electrolyte and gas-diffusion photoelectrodes with macroporous structures. The photoelectrodes are composed of n-type oxides for oxygen evolution reactions (OER) and are paired with a Pt electrocatalyst for hydrogen evolution reactions (HER). The review covers the conceptual framework of vapor-fed PEC hydrogen production, strategic design of gas-phase PEC reaction interfaces, and development of porous photoanodes such as titanium dioxide (TiO₂), strontium titanate (SrTiO₃), tungsten trioxide (WO₃), and bismuth vanadate (BiVO₄). A significant enhancement in PEC efficiency was achieved through the application of a thin proton-conducting ionomer film on these porous photoelectrodes for surface functionalization. The rational design of PEM-based PEC cells is crucial for realizing renewable-energy-driven hydrogen production from atmospheric humidity. The review highlights the potential of using atmospheric humidity as a hydrogen source, especially in regions with limited domestic renewable energy. It discusses the challenges of using liquid water for hydrogen production, such as gas bubble formation, the need for pumping, freezing in low temperatures, and leaching of toxic components. The use of water vapor offers advantages such as reduced maintenance costs and the ability to avoid the need for liquid water pumping systems. The review also discusses the development of porous photoanodes using titanium felt as a conductive substrate, focusing on the research efforts of the authors. The review presents recent progress in vapor-fed PEM-PEC cells based on the rational design of gas-diffusion oxide photoanodes and the triple-phase boundary concept under gas-phase conditions. It also provides suggestions for future work to improve the solar-to-hydrogen (STH) energy conversion efficiency of the PEM-PEC cell. The review covers the properties of porous semiconductor electrodes, including titanium dioxide, strontium titanate, and bismuth vanadate, and their applications in PEC water splitting. The review concludes that the development of PEM-PEC systems capable of operating in a gas-phase environment has significant potential for renewable energy-driven hydrogen production.This review discusses recent advancements in vapor-fed photoelectrochemical (PEC) systems for hydrogen production using water vapor as a hydrogen resource. The PEC system employs a proton exchange membrane (PEM) as a solid polymer electrolyte and gas-diffusion photoelectrodes with macroporous structures. The photoelectrodes are composed of n-type oxides for oxygen evolution reactions (OER) and are paired with a Pt electrocatalyst for hydrogen evolution reactions (HER). The review covers the conceptual framework of vapor-fed PEC hydrogen production, strategic design of gas-phase PEC reaction interfaces, and development of porous photoanodes such as titanium dioxide (TiO₂), strontium titanate (SrTiO₃), tungsten trioxide (WO₃), and bismuth vanadate (BiVO₄). A significant enhancement in PEC efficiency was achieved through the application of a thin proton-conducting ionomer film on these porous photoelectrodes for surface functionalization. The rational design of PEM-based PEC cells is crucial for realizing renewable-energy-driven hydrogen production from atmospheric humidity. The review highlights the potential of using atmospheric humidity as a hydrogen source, especially in regions with limited domestic renewable energy. It discusses the challenges of using liquid water for hydrogen production, such as gas bubble formation, the need for pumping, freezing in low temperatures, and leaching of toxic components. The use of water vapor offers advantages such as reduced maintenance costs and the ability to avoid the need for liquid water pumping systems. The review also discusses the development of porous photoanodes using titanium felt as a conductive substrate, focusing on the research efforts of the authors. The review presents recent progress in vapor-fed PEM-PEC cells based on the rational design of gas-diffusion oxide photoanodes and the triple-phase boundary concept under gas-phase conditions. It also provides suggestions for future work to improve the solar-to-hydrogen (STH) energy conversion efficiency of the PEM-PEC cell. The review covers the properties of porous semiconductor electrodes, including titanium dioxide, strontium titanate, and bismuth vanadate, and their applications in PEC water splitting. The review concludes that the development of PEM-PEC systems capable of operating in a gas-phase environment has significant potential for renewable energy-driven hydrogen production.