Synthesis, Structure, and Electrochemical Stability of Ir-Decorated RuO₂ Nanoparticles and Pt Nanorods as Oxygen Catalysts

Abstract

One major challenge of proton-exchange membrane fuel cells, water electrolyzers, and unitized regenerative fuel cells is to increase the oxygen catalysts' stability by the systematic preparation of inhomogeneous catalyst surfaces via decoration with cocatalysts. Iridium (Ir) nanodots with a typical diameter of 2 nm were colloid chemically deposited on ruthenium oxide (RuO 2 ) nanoparticles as oxygen evolution catalyst and on platinum (Pt) nanorods to yield bifunctional oxygen catalysts. The stepwise synthesis allows a higher control of the composite nanoparticles' morphology and thus their activity and stability. The stability toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was studied with cyclic voltammetry. Structural characterization was carried out with X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) spectroscopy before and after the stability protocols. Ir nanodots as well as Irdecorated RuO 2 nanoparticles were found to be less stable toward the OER stability protocol than pure RuO 2 nanoparticles. Bifunctional catalysts made of Ir deposited on Pt nanorods showed different behavior than the individual components. Concerning the OER, the stability decreased compared to unsupported Ir (monometallic OER catalyst), whereas improved stability was observed for the ORR in comparison to pure Pt nanorods (monometallic ORR catalyst).

Facile Synthesis of Nanoporous Pt‐Encapsulated Ir Black as a Bifunctional Oxygen Catalyst via Modified Polyol Process at Room Temperature

“…For the (311) and (222) crystalline planes, the corresponding peak positions are shifted to a larger angle compared with Pt black, which can be explained by the homogeneous compressive strain of Pt nanoparticles compared with the bulk material of Pt black. The same phenomenon has been observed by Gutsche and co‐workers . Additionally, the diffractogram of Pt 55 @Ir 45 shows broadened peak patterns due to the presence of Ir black.…”

Bifunctional electro-catalytic performances of CoWO4 nanocubes for water redox reactions (OER/ORR)

“…Pt, Ir, Rh, Ru etc.) or their oxides were widely used as the electroactive electrode materials in water electrolysis process for gas evolution and reduction reactions [6][7][8][9][10][11] but their uses as commercially are limited due to very high cost. Cobalt and tungsten are the earth abundant elements and CoWO 4 electrode materials could be efficient in water electrolysis reaction compared to noble electrode materials.…”

Electrochemical Reduction of CO2 on IrxRu(1–x)O2(110) Surfaces

“…RuxIr1-xO2 (110) surfaces are excellent model mixed oxide surfaces for studying catalytic properties. RuO2 and IrO2 have been widely researched as catalysts 18,25,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] . Both oxides are good band conductors 44 as required for electrocatalysis.…”