# Unveiling active sites and the cooperative role of non-thermal plasma and copper–zinc catalysts in the hydrogenation of CO2 to methanol

## TL;DR

This paper explores how non-thermal plasma and copper-zinc catalysts work together to convert CO2 into methanol, revealing new reaction pathways and mechanisms.

## Contribution

The study reveals a novel CO hydrogenation pathway and the role of Cu/ZnO interfaces in enhancing methanol yield under non-thermal plasma conditions.

## Key findings

- Zn enhances Cu dispersion and forms active Cu/ZnO interfacial sites that enable an additional CO hydrogenation route.
- Non-thermal plasma promotes gas-phase CO2 dissociation to CO, bypassing the reverse water–gas shift step.
- NTP stabilizes reduced Cu species, preventing re-oxidation and maintaining catalytic activity.

## Abstract

Methanol synthesis via non-thermal plasma (NTP) catalytic CO2 hydrogenation provides a sustainable approach to chemical and fuel production with potential in carbon emissions reduction. However, the underlying mechanisms remain unclear. Here we evaluate the mechanism of NTP-catalytic CO2 hydrogenation over Cu–Zn/ZSM-5 through operando X-ray absorption spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and in situ X-ray pair distribution function. We found that Zn enhances Cu dispersion and reducibility, as well as forming active Cu/ZnO interfacial sites. Beyond the conventional formate pathway on metallic Cu, these interfaces enable an additional CO hydrogenation route, enhancing methanol yield. NTP also promotes gas-phase CO2 dissociation to CO, bypassing the reverse water–gas shift step required in thermal catalysis. No Cu/Zn alloy formation was observed, underscoring the importance of metallic Cu and Cu/ZnO interfaces under NTP conditions. Furthermore, NTP stabilizes reduced Cu species, preventing re-oxidation and ensuring sustained catalytic activity. These findings advance the mechanistic understanding of NTP-assisted catalysis.

Plasmas can unlock unconventional reactivity for established catalytic systems, but understanding the resulting mechanistic changes is a complex endeavour. Here in situ characterization techniques allow us to rationalize the promotional role of non-thermal plasma on the catalytic hydrogenation of CO2 to methanol on Cu–Zn systems.