electrocatalysis

Electrocatalysis is the acceleration of electrochemical reactions at electrode surfaces through the use of electrocatalysts. It involves electron transfer at a solid–liquid interface and often a sequence of elementary steps that include adsorption of reactants, surface reactions, and desorption of products. Electrocatalysis aims to reduce activation barriers and overpotentials, improve reaction rates, and enable selective product formation in systems driven by an applied electrical potential.

Key principles include the Sabatier principle, which states that an optimal catalyst binds intermediates neither too weakly nor too strongly. Reactions frequently proceed via proton-coupled electron transfer and through complex surface pathways that depend on catalyst structure, electronic properties, and the local reaction environment. The performance of an electrocatalyst is described by metrics such as exchange current density, Tafel slope, overpotential, activity, selectivity, and stability, all of which are influenced by mass transport and the electrochemical double layer.

Common reactions studied in electrocatalysis include the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), as well as electrochemical CO2 reduction and nitrogen reduction. Catalysts span noble metals (e.g., platinum, iridium), transition metal oxides and chalcogenides, perovskites, carbon-based materials, and single-atom or nano-structured systems designed to optimize active sites and electron transfer.

Techniques such as rotating disk electrode methods, cyclic voltammetry, electrochemical impedance spectroscopy, and in situ spectroscopies are used to probe activity, kinetics, and mechanisms. Applications span energy conversion and storage, including water splitting, fuel cells, metal–air batteries, and sustainable chemical synthesis. Challenges include catalyst cost, stability, selectivity, and a detailed understanding of active sites and reaction mechanisms.