Hydrogen generation from atmospheric water

Green hydrogen, produced through water splitting using renewable energy, holds significant potential as an energy carrier in pursuing a low-carbon economy. However, the geographical mismatch between renewable resources and freshwater availability poses a significant challenge. This perspective analyzes the practicality of atmospheric water as an abundant source of hydrogen. We first examine the methodologies using a classical two-step process, i.e., sorption-based atmospheric water harvesting coupled with water splitting. We then dive into the state-of-the-art one-step process where atmospheric water is harvested and split directly via photovoltaic-electrochemical, photoelectrochemical, or photocatalytic processes. This perspective provides a comprehensive summary of innovative methodologies, emphasizes applications in (semi-)arid environments and outlines the technical challenges. By providing strategic guidance for developing efficient air-fed hydrogen generation technologies, the insight from this perspective aims to accelerate the deployment of hydrogen energy, especially in off-grid, distributed, or (semi-)arid communities, and propel advancements towards achieving a low-carbon and sustainable economy. Green hydrogen, produced by water splitting with renewables, faces water scarcity issues. Atmospheric moisture, a stable source, offers an alternative. This article reviews technologies and challenges of using atmospheric water for H2 production.