Oxygen evolution reaction on tin oxides supported iridium catalysts: Do we need dopants?

Application of oxide supports is considered as a viable approach to decrease iridium loading in oxygen evolution reaction catalysis in acid electrolyte. While the most of the promising oxides are poor conductors, the need for doping is typically taken as granted, and a representative example is tin dioxide. There are still, however, serious concerns on the feasibility of this approach as we lack consensus on any activity gain by using such oxides, while doubts on stability are numerous. In this work, a set of catalyst/support combinations including two catalysts, viz. hydrous (IrOx) and rutile (IrO2) iridium oxides, and four supports, viz. SnO2 and Sb‐ (ATO), F‐ (FTO), and In‐doped (ITO) SnO2, are synthesized and characterized by a selection of complementary experimental techniques including rotating disk electrode and on‐line inductively coupled plasma mass spectrometry. It is found that the electrochemical activity in acid media of supported Ir catalysts is essentially the same, independent on presence or absence of dopants. Sb and In dopants are shown to be unstable and cause an increased dissolution of Sn. Besides, the degradation of the doped supports results in destabilization of iridium oxides. These results raise doubts on the real need for the use of dopants in SnO2‐based catalyst supports for electrochemical water splitting.