Systematic Study of Oxygen Evolution Reaction Activity and Stability of SnnSbmNblOx Ternary Oxide-Supported IrO2 Catalysts

Abstract

Supporting IrO2 with conductive oxides has proven to be a practical way to increase the conductivity of the catalyst layer as well as decrease the anode IrO2 loading in proton exchange membrane electrolyzers. In this work, we proposed a high-throughput aerogel synthesis method to fabricate Sn–Sb–Nb ternary oxide supports. Their thermal stability, conductivity, and acidic stability were then systematically investigated; the results show that Nb addition decreases the ternary oxide’s conductivity by eliminating charge carriers. At the same time, Nb doping improves the thermal stability and increases the specific surface area of the ternary oxides; acidic stability is also increased with 5 at % Nb addition. IrO2 nanoparticles are deposited on selected oxide aerogels via the Adams fusion method to synthesize 50 wt % IrO2/SnnSbmNblOx catalysts. The catalytic performance and stability of catalysts with various supports were compared, revealing a boosted intrinsic activity than unsupported IrO2. The optimal ternary oxide support employed in this work was Sn80Sb15Nb5Ox. Its supported catalyst counterpart has a mass activity of 467 A g–1 at 1.6 V (vs reversible hydrogen electrode) and a Tafel slope of 43.43 ± 0.43 mv dec–1. Compared with other Nb doping amounts, 5 at % Nb catalyst dissolves Ir the least during the oxygen evolution reaction test, which we ascribed to Nb sacrifice. Moreover, the surface area of the supporting materials shows more remarkable influence on the resistance of the catalyst layer than their conductivity, which matters only when the supported catalysts have an approximate surface area. This finding also puts forward a strategy for the screening of supporting materials and provides valuable data for the design and prediction of supporting materials.