Reversible zinc oxidation as a route to on-demand hydrogen delivery

The transition to green hydrogen is limited by the absence of efficient synthetic pathways for on-demand, high-purity hydrogen at decentralized locations. Most solar and wind resources are located far from demand centres, and the infrastructure costs of hydrogen pipelines make them economically unfeasible for widespread deployment. Here we report a reversible energy vector-mediated synthetic pathway that uses metallic zinc for hydrogen distribution. Machine learning-guided screening identified lactate as a ligand that outcompetes hydroxide for Zn(II) coordination in alkaline media, doubling the soluble Zn(II) concentration to 1.12 M and enabling self-sustained, circuit-free hydrogen production. The system operates between 0 and 80 °C with approximately 99% Faradaic efficiency and achieves a volumetric hydrogen capacity of 137.9 to 218.4 kg H 2  m −3 , exceeding, to the best of our knowledge, many established and state-of-the-art carriers. This approach offers improved safety and practical deployment compared with existing carriers, providing on-demand green hydrogen for remote communities, mobile platforms and off-grid industrial sites.