mAcm2

mA/cm^2, or milliampere per square centimeter, is a unit of electric current density used in electrochemistry and related fields. It denotes the current I flowing through an electrode surface per unit area A, expressed as J = I/A. When using this unit, I is typically measured in milliamperes and A in square centimeters, making 1 mA/cm^2 equal to 10 A/m^2.

This unit is practical because reaction rates at electrodes depend on current density, not just total current, and allows comparison across electrodes of different sizes. It is widely used in electroplating and electrolysis to specify deposition rates, in corrosion testing to report uniformity of metal loss, in battery and supercapacitor testing to characterize charge–discharge processes, and in photoelectrochemical and solar cell research to report photocurrent densities. The exact value that constitutes a "high" or "low" density depends on the chemistry, electrode material, electrolyte, temperature, and surface area.

Measurement and reporting considerations: the electrode area must be known, and the distinction between geometric area and electrochemically active area can matter, especially for rough or porous electrodes. Current density is typically controlled with a potentiostat/galvanostat, while the area is documented to enable reproducible comparisons. Conversion to SI units is straightforward: 1 mA/cm^2 = 10 A/m^2.

In summary, mA/cm^2 is a practical, widely used unit describing how much current passes per unit surface area at an electrode, serving as a key metric for reaction rates and device performance in electrochemical systems.