Lateral Size Effects of Two-dimensional IrO2 Nanosheets towards the Oxygen Evolution Reaction Activity

The oxygen evolution reaction of anode catalyst is an important reaction in polymer electrolyte membrane water electrolysis. Recent research has focused on understanding the factors governing the catalytic properties of nanostructured IrO2 in order to decrease the use of expensive and precious IrO2. We demonstrate here the equivalent diameter (D-e) effect (lateral size effect) of IrO2 nanosheets for the oxygen evolution reaction. IrO2 nanosheets with four different D-e from 110 to 260 nm and same thickness (similar to 1.5 nm) were prepared. The electrical double layer capacitance, which should be proportional to the electrochemically active surface area, of IrO2 nanosheets was independent of D-e. On the other hand, the pseudo-capacitance, which is related to surface redox processes, and the oxygen evolution reaction activity increased with decreasing D-e. The enhanced oxygen evolution reaction activity is discussed based on the electrochemically active surface area and edge effect. (C) The Electrochemical Society of Japan, All rights reserved.