Electrolyzers

An electrolyzer is a device that uses electrical energy to drive the electrolysis of water, producing hydrogen and oxygen. It consists of an electrolyte or membrane, electrodes, and a separator to prevent gas mixing. When current is applied, water is oxidized at the anode to form oxygen, while at the cathode protons or water molecules are reduced to form hydrogen. The specific design depends on the electrolyte and operating conditions.

There are several main types. Alkaline electrolyzers use a liquid electrolyte (often potassium hydroxide) and nickel-based electrodes. Proton exchange membrane (PEM) electrolyzers employ a solid polymer electrolyte that conducts protons and typically use noble-metal catalysts. Solid oxide electrolysis cells (SOEC) operate at high temperatures and use a ceramic electrolyte to reduce water with steam, potentially improving efficiency but presenting materials durability challenges. Anion exchange membrane (AEM) electrolyzers, using a solid anion-conducting membrane, are an emerging variant.

Efficiency and operation vary by technology and conditions. Electrical-to-hydrogen efficiency is commonly in the range of about 60% to 75% (LHV), with higher-temperature or high-pressure operation offering trade-offs. PEM systems are typically responsive to dynamic power input, while SOECs offer potential efficiency gains when heat integration is feasible but require robust materials. Hydrogen produced can be delivered at ambient pressure or pressurized for storage and transport; oxygen is typically vented or captured for industrial use.

Applications include on-site hydrogen production for industrial processes, fueling hydrogen-powered vehicles, and seasonal or grid balancing when integrated with renewable electricity. Economics depend on electricity costs and capital expenditure, and ongoing research targets lower materials costs, longer lifetimes, and better integration with energy systems. Safety considerations address hydrogen handling, gas separation, and proper ventilation.