(124f) Discovery of Intermetallic Electrocatalysts for CO Reduction Viaelectronic Structure Engineering

The electrochemical reduction of CO₂ enables carbon-neutral fuels and chemicals to be produced using intermittent renewable electricity. However, monometallic Cu is the only electrocatalyst capable of selectively driving the reaction and it does so with an inadequate energy efficiency to make the process economically viable. The unique ability of Cu to catalyze this reaction has been attributed to its moderate CO adsorption energy, which is unique among transition metals. This unique adsorption energy is a direct result of the unique d-band structure of Cu. Thus, the unique d-band structure of Cu may be what enables it to catalyze this reaction. As a result, systematic electronic structure tuning provides a viable route toward the discovery of novel electrocatalysts with superior activity. Electronic modifications of this magnitude can be induced through intermetallic bonding between electronically dissimilar metals. Interestingly, several Cu-free intermetallic alloys have been shown to exhibit Cu-like electronic structures, chemical reactivities, and catalytic activities for a variety of other reactions, such as methanol synthesis and steam reforming.

In this presentation, we will explore the impact of systematic electronic structure modifications on the CO reduction activity of several Pd-based intermetallic alloys. We find that such alloys exhibit nearly identical d-band structures and chemical reactivities as Cu. However, we also observe that such alloys instantaneously segregate upon air exposure, preventing their electrocatalytic activity to be accurate probed using conventional approaches. To circumvent this challenge, we propose and validate a generic experimental methodology that protects intermetallic surfaces from segregation using a sacrificial passivating overlayer that can be easily and selectively removed in an electrochemical environment under potential control. We then demonstrate the impact of electronic structure modifications on the CO reduction activity of these Pd-based intermetallic alloys.