Is the catalytic current always proportional to the surface area of an electro-catalyst?

Benchmarking electrocatalytic nanoparticles typically assumes that the current is proportional to the surface area of the active material. We theoretically and experimentally demonstrate using numerical simulations and hydrazine oxidation on gold nanoparticles that only a limited range of active material coverage obeys this assumption. We provide guidelines to correctly assess the electrocatalytic activity of dispersed materials.