An Electrochemical Neutralization Cell to Harvest the Water Formation Energy

Abstract

The transition from a carbon-based to a hydrogen-based economy is inevitable, given the growing global energy crisis fuelled by rising energy demands due to rapid population and economic growth. However, the widespread adoption of hydrogen economy faces challenges, particularly the high energy requirements in key stages such as hydrogen production, purification, and utilization. In this context, harvesting electrochemical water formation energy using a decoupled acid-alkali system offers significant advantages for driving electrochemical reactions in various energy conversion devices. Despite its promising thermodynamic aspects and technological implications, the water formation reaction faces barriers to its electrochemical applications due to its non-redox nature. This thesis focuses on overcoming this limitation by electrochemically harnessing water formation energy as an electromotive force using hydrogen redox. The energy derived from the water formation reaction is captured and used for various electrochemical process modulations, by exploiting the pH-dependent hydrogen redox in a decoupled acid-alkali system. By introducing a heat gradient to the water formation cell, this energy extraction process can be further enhanced due to the positive entropy change of water formation reaction pathway. A tangential dimension of harvesting water formation energy is demonstrated by hydrogen fuel purification during the delivery of electric power. This system purifies hydrogen contaminated with hydrocarbons, CO₂, and N₂—common impurities in steam reformer exhaust—at room temperature and pressure while simultaneously generating electric power. This makes the purified hydrogen immediately usable in a proton exchange membrane fuel cell (PEMFC). This process eliminates the need for energy-intensive conventional purification methods, which often hinder economic sustainability. Additionally, it utilizes poison-resistant electrocatalysts to remove contaminants like CO and sulfur compounds under ambient conditions, making the process more efficient and cost-effective. The thesis also explores a unique application of water formation energy to generate heavy hydrogen under ambient conditions while simultaneously producing electrical energy, thereby converting light hydrogen into heavy hydrogen. In summary, this thesis demonstrates strategies for utilizing water formation energy for spontaneous hydrogen purification, fuel detoxification, low-grade heat harvesting, and heavy hydrogen generation while expanding the scope of the hydrogen economy into unchartered territories.