Thermal-assisted low-energy hydrogen production through a thermoregenerative ammonia-decoupled water electrolysis system

Conventional water electrolysis faces challenges due to the tight link between the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), including gas mixing risks and high energy use. This study introduces a new decoupled system using a thermoregenerative ammonia electrolyte. It enables separate hydrogen and oxygen production while significantly reducing energy consumption. The key approach is to replace the high-energy HER with electrochemical reduction of Cu 2+ , while storing protons (H + ) through the OER. A major innovation is adding ammonia gas, which reacts spontaneously with the deposited copper to reduce the stored H + and produce hydrogen. This allows "on-demand" hydrogen generation without external power. The system operates at a cell voltage about 50% lower than that of conventional water electrolysis, as low as 1.31 V. Reaction agents are recycled through low-temperature thermal breakdown of the copper-ammonia complex, achieving a specific energy consumption for hydrogen production as low as 5.02 kWh·m −3 H 2 , matching top-tier performance. By separating energy input from hydrogen output in time and space, this research offers a new direction for flexible and efficient hydrogen production.