Pt-Ru and Pt-Mo electrodeposited onto Ir-IrO2 nanorods and their catalytic activities in methanol and ethanol oxidation

Pt-Ru and Pt-Mo electrocatalysts are prepared via pulse electrodeposition of Pt, Ru, or Mo on a reduced IrO2 nanorod (Ir-IrO2NR) array. High-resolution TEM analysis shows the 3-6 nm Ir nuclei are preferentially aligned, with Ir(110) lattice fringes parallel to the growth direction of the IrO2 rod. XPS analysis indicates Pt, Ru and Ir on the catalytic surface exist in the metallic state, and Mo is in the 4+ and 6+ oxidation states. The grains of Ir, nucleated by IrO2 reduction, initiate the catalytic activity, as evidenced in the emergence of a prominent COads oxidation peak in a broad potential range (0.36-0.90 V). The COads oxidation activity is strongly influenced by the later electrodeposited Pt-Ru and Pt-Mo, and so are the activities toward methanol and ethanol oxidation. The Ru decoration narrows down the broad COads oxidation potential range and shifts the peak to a lower potential so that PtRuIr- (at high voltage) and RuPtIr-IrO2NR ( at low voltage) exceeds the performance of a commercial catalyst. The Mo decoration changes the activity such that PtMoIr- and MoPtIr-IrO2NR catalysts are more suitable for ethanol oxidation, even though the Mo promotion on COads oxidation is moderate.