Impact of Surface Charging on Catalytic Processes

TL;DR

This paper introduces a new computational method to study the effects of surface charges on catalysts, revealing that negative charging enhances CO2 activation and can tune catalyst activity and selectivity.

Contribution

The authors develop a practical density functional approach for charged systems, enabling detailed analysis of surface charging effects on catalytic processes.

Findings

Negative surface charge significantly boosts CO2 reduction to CO.

Charging alters the activity hierarchy of transition metal catalysts.

Controlled surface charging can tune catalyst selectivity.

Abstract

Although significant insights have been obtained into chemical and physical properties that govern to the performance of catalysts in traditional thermal processes, the work on electro-, photo-, or plasma-catalytic approaches has been comparatively limited. The effect of (local) surface charges in these processes, while most likely a crucial factor of their activity, has not been well-characterized and is difficult to study in a consistent, isolated manner. Even theoretical calculations, which have traditionally allowed for the untangling of the atomic-level mechanisms underpinning the catalytic process, cannot be readily applied to this class of problems because of their inability to properly treat systems carrying a net charge. Here, we report on a new, generic, and practical approach to deal with charged semiperiodic systems in density functional calculations, which can be readily applied to problems across surface science. Using this method, we investigate the effect of a negative catalyst surface charge on CO$_2$ activation by supported M/Al$_2$O$_3$ (M = Ti, Ni, Cu) single atom catalysts. The presence of an excess electron dramatically improves the reductive power of the catalyst, strongly promoting the splitting of CO$_2$ to CO and oxygen. The relative activity of the investigated transition metals is also changed upon charging, suggesting that controlled surface charging is a powerful additional parameter to tune catalyst activity and selectivity.