watersplitsing

Watersplitsing, or water splitting, is the chemical process of decomposing liquid water into hydrogen and oxygen. The most common method is electrolysis, but water splitting can also occur via photolysis using light energy or by high-temperature thermolysis. The primary motivation is the production of hydrogen as a clean energy carrier and as a chemical feedstock.

Electrolysis involves passing an electric current through water (often with an electrolyte) between two electrodes. The cathode produces hydrogen while the anode releases oxygen. The overall reaction is 2 H2O -> 2 H2 + O2. Efficiency is limited by overpotentials, resistance, and water purity; practical systems use membranes and catalysts to reduce energy losses and separate the gases.

Photocatalytic or photoelectrochemical water splitting uses light-activated catalysts to drive the reaction, potentially directly from sunlight. Thermolysis relies on high temperatures to provide the energy for water decomposition. These approaches aim to reduce electricity demand or enable solar-driven hydrogen production, but challenges include catalyst stability, material cost, and achieving competitive efficiency.

History: The first electrolysis of water was demonstrated in 1800 by William Nicholson and Anthony Carlisle. Faraday later formalized the relationship between electric charge and the amount of substance produced (Faraday's laws). Since the late 20th century, research has focused on durable catalysts, membrane technologies, and integration with renewable energy.

Applications and challenges: Green hydrogen produced from water splitting can support decarbonization of industry and transport, and serve as energy storage. Barriers include the high electricity input required, capital costs for electrolyzers, durability of materials, and safe storage of hydrogen. Advances in catalysts, materials, and process design continue to address these issues.