Effects of catalyst mass loading on electrocatalytic activity: An example of oxygen evolution reaction

The evaluation of the intrinsic activity of catalysts is the most basic in searching energy- and cost-efficient catalyst materials for various applications. The accurate determination of the intrinsic activity is essential for identifying efficient catalysts. While a huge number of studies of electrocatalysis for various applications have been reported, the effects of electrode loading on the apparent intrinsic activity obtained experimentally have been rarely discussed. With a high mass loading on the electrode, not all the catalyst surfaces can be electrochemically active because not all the surfaces can be wetted by the electrolyte. The loading also affects the transport of electrons over the electrode as well as the transport of ions in the electrolyte, and thus affects the kinetics. These lead to the derivations of the apparent intrinsic activity from the real intrinsic activity. Herein, for better understanding the derivations, we evaluate and discuss the effects of electrode mass loading using oxygen evolution reaction as an example.