Decentralized Green Hydrogen Production via Sorbent-Based Atmospheric Water Harvesting in Extreme Arid Conditions

<div style="direction: ltr;">The urgent need for decarbonizing the energy sectors has resulted in the use of green hydrogen (H₂) as a clean alternative to fossil fuels. Green hydrogen produced by water splitting using renewable energy, such as solar, stands out as a leading energy medium for a carbon-neutral world. However, splitting water using natural sunlight cannot meet the amount of H₂ needed to fully decarbonize the energy sector. Currently, state-of-the-art solar-powered green hydrogen production systems tend to suffer from two fundamental limitations. Typically, the latter systems consume a significant amount of water, limiting the deployment of such systems to places where water is available. Additionally, these systems have very low efficiencies (< 10%) due to inefficiencies in energy conversion. To enable decentralized green hydrogen production, we develop a novel method that optimizes water splitting by leveraging the ability to harvest water in arid environments using sorbent-based atmospheric water harvesting (SAWH) and solar energy. This results in a system capable of producing green hydrogen directly from the air (at relative humidity > 10%). We meticulously designed and integrated the sorbent, electrolytic cell, and PV panel, aiming to achieve a record-high system efficiency of > 20%.</div> <div style="direction: ltr;">This study investigates several critical aspects of this method: (1) Sorbent integration; (2) enchantment of PEM cell wettability by biphilic nanostructured porous media; and (3) optimizing the daily electrical and thermal energy harvesting to water and hydrogen production ratio. Detailed insights into the selection and integration of sorbent materials by isotherms and kinetics at low temperatures and compatibility with PV panels are studied. Achieving the optimal balance between sorbent properties, long-duration desorption-based PV cooling, and sufficient water production at arid conditions is critical for efficient hydrogen production. The nanostructured biphilic condenser's functionality in maintaining the PEM wetness while enhancing the water and oxygen transport is also explored. Achieving a balance between wettability and gas diffusion is essential for hydrogen production in a high vapor-enclosed system.</div> <div style="direction: ltr;">To ensure a continuous and reliable hydrogen supply, aligning the momentary electricity production from PV panels to the optimal hydrogen generation loads is crucial. Additionally, solar heating loads must be matched to daily water production to ensure continuous regulation of the PV panel temperature. Therefore, this study delves into strategies for maximizing solar energy utilization to reach maximum solar to hydrogen production efficiencies. Finally, this study presents an experimental proof-of-concept of generating green hydrogen from arid air and assesses its potential to enable a fully sustainable approach with zero emissions. As we strive towards a cleaner and more sustainable future, this innovative approach holds great promise as a viable solution for hydrogen production from the atmosphere.</div>