A membrane electrode assembly (MEA) is a layered electrochemical component built around an ion-conducting membrane and functional electrode layers. In proton-exchange-membrane fuel cells and electrolyzers, the MEA brings together the membrane, anode catalyst layer, and cathode catalyst layer; gas-diffusion or porous transport layers are often adjacent components in the assembled cell.

A catalyst-coated membrane (CCM) is an ion-conducting membrane with catalyst layers deposited directly onto one or both sides. It is widely studied in proton-exchange-membrane fuel cells and water electrolyzers because the direct membrane–catalyst interface can support short ionic pathways and compact assembly. Its performance depends on membrane integrity, catalyst-layer structure, and the quality of each interface.

A catalyst layer is a thin, engineered region containing catalytic material and supporting components that enable electrochemical reactions. It is commonly integrated into fuel-cell electrodes, water-electrolysis electrodes, and other electrochemical devices. Its performance depends on more than catalyst chemistry: thickness, porosity, ionomer distribution, electrical contact, wetting, and adhesion also shape the accessible reaction area.

A catalyst ink is a formulated suspension or dispersion containing catalytic material and a liquid medium, often with ion-conducting polymer, binder, or other additives. It is applied to a substrate to create a catalyst layer for electrochemical devices and research electrodes. Ink formulation strongly affects deposition, drying, microstructure, adhesion, and ultimately the measured electrode response.

Faraday's law connects the amount of chemical change at an electrode with the total electric charge passed through an electrochemical system. It is used to estimate deposited mass, gas production, reactant conversion, and current efficiency. In research and process development, it helps connect electrical operating conditions to expected material production.

The Nernst equation relates an electrode's equilibrium potential to the standard potential and the activities or concentrations of the chemical species involved. It explains why measured electrochemical potential changes with concentration, temperature, and reaction composition. For laboratory researchers, it provides a bridge between thermodynamics and the conditions present in a real electrochemical cell.