Alkaline Methanol Electrooxidation on Bi-Modified Pt 3 M Intermetallics: Kinetic Origins and an OH Binding Energy Descriptor

The exploration of advanced CO-free catalysts and clarifying the ambiguous kinetic origins and governing factors would undoubtedly open up opportunities to overcome the sluggish kinetics of methanol electro-oxidation and promote the development of direct methanol fuel cells. Herein, we constructed a family of Bi-modified Pt3M intermetallic catalysts (Bi–Pt3M/C) that follow a CO-free dominated pathway. More significantly, we have identified the pivotal factor governing the reaction kinetics in the CO-free pathway, namely, OH binding energy (OHBE). This is because the rate-determining step (RDS) involves both C–H bond activation and water dissociation, and the energy barriers of these processes are effectively captured by OHBE. Accordingly, OHBE can act as an activity descriptor. Specifically, Bi–Pt3In/C stands out from other Bi–Pt3M/C and delivers the mass activity of 36.7 A mgPt–1 at peak potential, far exceeding state-of-the-art Pt-based catalysts reported to date. Taking Bi–Pt3In/C as a proof of concept, we elucidate the origin of enhanced MOR activity by combining theoretical calculations, kinetic isotope effects, and formaldehyde electrooxidation. Moreover, there exhibits a volcano-type trend between OHBE and the activity of Bi–Pt3M/C. Beyond the discovery of ultrahigh-performance catalysts, these findings provide a detailed mechanistic picture of RDS and offer an innovative design principle for advanced catalysts.