Characterization of electrocatalysts for the oxygen evolution reaction OER: a bi-metal study IrM oxides (Ru, and Au)

Abstract The costs of producing electrocatalysts needed for proton exchange membrane water electrolyzers can be reduced by using less expensive metals, such as ruthenium, instead of the commercially used IrO. This reduction is needed for two reasons: 1) although South Africa has the central reserves globally, iridium is a scarce element that is mined with other platinum group metals (PGMs), and 2) iridium is 4 times more expensive in comparison to platinum. Hence, efficient bimetallic (IrM oxides where M = gold or ruthenium) electrocatalysts are needed for water splitting in acidic conditions. This paper reports on the commercial benchmark IrO and compares its electrocatalytic activity to the lab-synthesized IrRu and IrAu oxide composite mixtures. The benchmark catalyst IrO reported an onset potential of 1.23 V compared to the IrRu blended mixtures, with an average overpotential of 0.15 V. The IrAu oxide composites reported a slightly higher value of 0.28 V. The Tafel slopes for IrO were found to be 69.6 mV/decade, the IrAu oxides prepared reported an average of 52.61 mV/decade and the IrRu oxides an average of 65.65 mV/decade. Therefore, the IrAu showed good activity and OER stability compared to the commercial catalyst.