Oxygen Evolution Reaction on Tin Oxides Supported Iridium Catalysts: Do We Need Dopants?

Abstract

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 (IrO x ) and rutile (IrO 2 ) iridium oxides, and four supports, viz. SnO 2 and Sb-(ATO), F-(FTO), and In-doped (ITO) SnO 2 , are synthesized and character-ized 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 SnO 2 -based catalyst supports for electrochemical water splitting.

Oxygen Evolution Reaction Activity and Stability Benchmarks for Supported and Unsupported IrOx Electrocatalysts

“…The instability of ATO supports in high potential conditions has been ascribed to the preferential leaching of Sb atoms segregated at their surface. 16,32,[44][45][46][47] .…”

Enhancing Iridium Nanoparticles’ Oxygen Evolution Reaction Activity and Stability by Adjusting the Coverage of Titanium Oxynitride Flakes on Reduced Graphene Oxide Nanoribbons’ Support

“…Another difference in Ir catalysts' stability is related to the oxidation state of the nanoparticles. The hydrous (amorphous) IrO x is less stable than rutile (crystalline) IrO 2 , [57,69,91,92] and it was previously shown that on the same support (ATO), IrO x was dissolving more during cleaning cycles than its IrO 2 counterpart. [57] In our case, Ir XRD diffraction peaks of the "asprepared" samples are similar (Figure 1), which suggests that all samples contain Ir with the same oxidation state.…”

Effect of the Morphology of the High-Surface-Area Support on the Performance of the Oxygen-Evolution Reaction for Iridium Nanoparticles

“…Additionally, the stability and electronic catalyst–support interactions, as well as the economic criteria, need to be taken into account. 11 , 14 − 16 Given the stated requirements, a promising substitute for carbon is titanium oxynitride (TiON x ), which can be prepared from titanium dioxide (TiO 2 ) 17 or titanium nitride (TiN) 18 in the form of various nanostructures. 19 − 21 There are different synthesis methods to choose from.…”