Adding refractory 5d transition metal W into PtCo system: an advanced ternary alloy for efficient oxygen reduction reaction

Abstract

Tungsten (W), as a refractory 5d transition high-valency metal with unique physical and chemical properties, can substantially improve Pt-based alloys, providing a superior electrocatalytic performance for the oxygen reduction reaction (ORR), which is considered a key cathode process in fuel cell automotives or portable devices. In this study, we developed a graphene-supported Pt–Co–W ternary alloy, by using a facile one-pot polyol co-reduction of the above three metals. In 0.1 M HClO₄ solution, the obtained Pt–Co–W ternary alloy exhibited a surprisingly high specific activity of 3.41 mA cm⁻², which is 4.3 times higher than that of the well-known Pt–Co binary alloy (0.80 mA cm⁻²) and 13 times more than that obtained by the state-of-the-art Pt/C (0.27 mA cm⁻²). The mass activity of the alloy was 2.25 A mg_Pt⁻¹, which is 4.2 times higher than that of the Pt–Co binary alloy (0.53 A mg_Pt⁻¹) and 12 times higher than that obtained by the state-of-the-art Pt/C (0.19 A mg_Pt⁻¹) at 0.9 V versus a reversible hydrogen electrode (RHE). The remarkably enhanced ORR activity could be attributed to the incorporation of a small amount of W into the Pt–Co alloy system at an atomic level. The added W atoms could not only strengthen the chemical adsorption of oxygen molecules but also significantly facilitate desorption of the oxygenated species on the active Pt sites in this ternary alloy, because W has a stronger electronegativity, higher unsaturated 5d orbitals, and higher valency coordinated with these oxygenated groups. Therefore, introducing cheap refractory transition metals, like W, into Pt-based binary alloys may open a door to fabricate efficient next-generation ternary catalysts for the ORR.