Electrocatalysts

Electrocatalysts are materials that accelerate electrochemical reactions at electrodes by providing active sites that lower activation barriers and/or overpotentials. They are central to energy conversion and storage technologies, including water electrolysis, fuel cells, and metal‑air batteries. Most practical electrocatalysts are heterogeneous catalysts consisting of active solid materials dispersed on supports in contact with electrolytes. They can be metal, alloy, metal oxide, or carbon-based systems, and increasingly include single-atom catalysts and two‑dimensional materials.

Key reactions include the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting, and the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) in fuel cells. The performance is governed by metrics such as overpotential, Tafel slope, exchange current density, Faradaic efficiency, and electrochemical surface area. Stability under operating conditions, tolerance to poisons, and resistance to dissolution are critical for practical devices.

Common materials include platinum-group metals for ORR and HER, mixed-metal oxides and nitrides for OER, and earth-abundant catalysts based on Ni, Co, Fe, and Mn. Design strategies combine alloying, doping, core–shell architectures, defect engineering, and optimized supports to increase activity, selectivity, and durability. Emerging approaches such as single-atom catalysts and doped carbon frameworks aim to maximize atom utilization and lower costs, while operando characterization guides understanding of active sites.

Applications span proton-exchange membrane and alkaline electrolyzers, fuel cells, zinc–air and Li–air batteries, and carbon dioxide or nitrogen reduction electrocatalysis. Despite advances, challenges remain in achieving high performance with low cost, ensuring long-term stability, and scalable synthesis.