Enhancing Ethanol Electrooxidation Stability over PtIr/GN Catalysts by In Situ Formation of IrO2 at Adjacent Sites

Abstract

PtIr alloy is considered as one of the most promising catalysts for ethanol electrooxidation due to its excellent C–C bond breaking and dehydrogenation abilities. However, a small amount of intermediate species produced by ethanol oxidation can still poison Pt, thereby affecting the stability of ethanol oxidation. Here, graphene supported PtIr nanoparticles (PtIr/GN) with a Pt: Ir atomic ratio of 3:1 is synthesized by a simple hydrothermal reduction and thermal annealing. The physicochemical analyses show that IrO2 is formed in situ in PtIr/GNs (O) during annealing and located adjacent to PtIr alloys. IrO2 and PtIr are evenly dispersed on GNs. The electrochemical results indicate that PtIr/GNs (O) has higher catalytic activity and stability for ethanol electrooxidation than PtIr/GNs. After 1000 voltammetric cycles, the peak current density for PtIr/GNs (O) is 2.5 times higher than that for PtIr/GNs. The outstanding electrochemical performance of PtIr/GNs (O) is derived from PtIr alloy that promotes the cleavage of the C–C bond and weakens the adsorption of Pt to intermediate species, IrO2 that improves the tolerance of Pt to CO-like species and enhances the structural stability of Pt, and PtIr alloy and IrO2 in adjacent positions that synergistically improve the stability of catalytic ethanol oxidation.