Low-temperature plasma (LTP) catalysis is a growing field of research, reporting synergistic effects for increased activity, yield, or selectivity compared to conventional thermocatalytic approaches. LTP can activate stable molecules such as CO2 via interactions with high-energy electrons. Still, the many effects that LTP has on surface-catalyzed reactions are multi-faceted and poorly understood at an atomistic level. It would help to understand the effects of plasma on a catalyst surface by studying each in isolation. For instance, the LTP contains many charged particles and excited electrons, and this causes a negative charge to accumulate on the exposed surface. In this work, we study the effect of surface charge due to LTP in isolation for the CO2 reduction reaction. Using density functional theory modeling, we study single-atom catalyst systems across the periodic table to understand the importance of surface charging on CO2 activation. We analyze six different metals (Co, Ni, Cu, Rh, Pd, and Ag) as dispersed metal ions. These metals are dispersed on three different supports (CeO2, TiO2, Al2O3), each with varying levels of reducibility. Our modeling approach is adapted from recent literature and applied to study the plasma’s effect on catalytic activity. We add a negative charge to the single metal atom on the catalyst surface and a counterion (H+) to the vacuum layer to maintain overall neutrality. This simulates an electric field that can be tuned by varying the distance between point charges. We predict CO2 binding energy and reaction barrier trends to characterize each system’s catalytic activity. Our results show that the adsorption and reaction trends for CO2 reduction differ between plasma and thermal catalysis, implying that insights from one field may not necessarily apply to the other.

Influence of plasma-induced surface charging on single-atom catalysis for CO2 reduction

ACS Spring 2022

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