Unlocking the catalytic potential of tungsten carbide coordinated with 3d transition metals in oxygen electrochemistry

Abstract

As one of the keystones of electrochemistry, the oxygen reduction reaction (ORR) offers an enthralling approach to oxygen monitoring, and energy conversion/storage. At present, only 3d transition metals (TMs)-based catalysts have proven to be reliable options for electrochemical O2 activation, while non-3d TM catalysts such as 5d tungsten (W) typically exhibit much lower electrochemical ORR activities. Herein, we propose a simple and controllable approach for accelerating the ORR and oxygen evolution reaction (OER) on the surface of tungsten carbides coordinated with 3d metal, i.e., TM3W3-xC (TM=Mn, Fe, Co, Ni, and Cu). Among them, Mn3W3-xC is found to display exceptional ORR activity (Eonset = 0.83, and E1/2 = 0.73 V), which is on par with that of the commercial Pt/C catalyst (Eonset = 0.84, and E1/2 = 0.75 V) in alkaline media. Furthermore, Mn3W3-xC has outperformed Pt/C in terms of durability and methanol resistance due to the carbon shell protecting the metal nanoparticles from agglomeration or dissolution in alkaline media. The coordination of Mn centers to the W3-xC surface not only allows the precise regulation of the electronic structure of W ions but also creates dual-metal sites (MnW) to facilitate interfacial charge transfer. Such electron transfer enables the MnW surface more electrophilic, in turn increasing its affinity for hydroxide ions. As a result, the MnW coordinated with the carbide surface has OER-favorable MnW-oxo and MnW-hydroxo configurations within their oxidized surfaces. Overall, this research discovered that the catalytic potential of inactive W elements in oxygen electrochemistry can be unlocked by coordinating with 3d TMs.