(726g) Rational Design of Intermetallic Electrocatalysts for CO Reduction

The electrochemical reduction of CO₂ offers a potential means of storing intermittent renewable electricity in the form of energy dense carbon-neutral chemical fuels that are compatible with our existing energy infrastructure. Unfortunately, the electrocatalysts currently available for CO₂ reduction are neither active nor selective enough to make the process industrially viable. Furthermore, research efforts aimed at discovering new electrocatalysts have failed to identify materials with superior activity or selectivity to pure metallic copper. However, recent studies have demonstrated that CO₂ can be efficiently reduced to CO, an intermediate in the reduction of CO₂ to hydrocarbons and alcohols over copper, and that the efficiency of CO reduction over copper increases concomitantly with the pH of the electrolyte. Despite these observations, no studies have attempted to identify alloy electrocatalysts capable of efficiently catalyzing the reduction of CO to hydrocarbons and alcohols in alkaline electrolytes.

In this presentation we will outline a rational means of designing Cu-free intermetallic electrocatalysts for CO reduction in alkaline media that utilizes the d-band valence electronic structure as the descriptor of electrocatalytic activity. We will demonstrate how the d-band valence electronic structure of transition metals can be systematically modified via the formation of strong intermetallic bonds with electronically dissimilar metals and how such modifications impact their electrocatalytic activity. We will demonstrate that composition gradients form in the near-surface region of such intermetallic alloys upon air exposure using both x-ray photoelectron and ion scattering spectroscopies. Unfortunately, these previously unidentified near-surface composition gradients cast doubts on the conclusions of prior studies of the electrocatalytic activity of similar intermetallic systems for CO and CO₂ reduction. Finally, we will present a novel experimental methodology that enables the formation of these near-surface composition gradients to be completely avoided.