Breaking through the peak height limit of the volcano-shaped activity curve for metal catalysts: role of distinct surface structures on transition metal oxides

The volcano-shaped activity curve has long been used to reveal the activity trends among different catalysts and is a fundamental tool for catalyst screening. Although generally the peak height of the curve is considered as the highest possible activity, the understanding for its origin and inherent constraints is still a comparatively open issue. Herein, on the basis of microkinetic analysis and first-principles calculations, we quantitatively demonstrate that the peak height is strongly affected by the structural features of catalyst surfaces and could be largely improved by reducing the intercept of the Brønsted–Evans–Polanyi (BEP) relation. Focusing on various transition metal oxides (TMOs), we explore the BEP relations for the dissociation of small molecules, and the intercepts are shown to be smaller than those of flat metals. This reduction in intercept originates from the distinct local structure of oxide surfaces, which contributes to the weak binding ability and more final-state-like transition state. Taking NO oxidation as an example, we illustrate that the activity curve of rutile-type oxides is obviously higher than metals at typical medium–high temperatures, suggesting that rutile-type oxides possess inherently superior activity. Furthermore, general application of TMOs in breaking through the activity limit of metals for molecule dissociation is discussed.