Pt–Ru and Pt–Mo electrodeposited onto Ir–IrO2nanorods and their catalytic activities in methanol and ethanoloxidation

Abstract

Pt–Ru and Pt–Mo electrocatalysts are prepared via pulse electrodeposition of Pt, Ru, or Mo on a reduced IrO₂nanorod (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 IrO₂reduction, initiate the catalytic activity, as evidenced in the emergence of a prominent CO_adsoxidation peak in a broad potential range (0.36–0.90 V). The CO_adsoxidation 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 CO_adsoxidation 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 CO_adsoxidation is moderate.