# Multi-Scale Modeling for Plasma-Enhanced Ammonia Decomposition over Carbides and Nitrides

## TL;DR

This paper explores how non-thermal plasma can enable efficient ammonia decomposition at lower temperatures using cobalt-based carbides and nitrides as catalysts.

## Contribution

A novel multiscale modeling framework is introduced to study plasma-enhanced ammonia decomposition over Co-based catalysts.

## Key findings

- Co3C(001) and Co3N(001) show significantly lower required temperatures for ammonia decomposition compared to Ru and Co under thermal conditions.
- Plasma-induced vibrational excitation shifts the rate-limiting step to NH3(v1) dissociation, increasing turnover frequencies by up to six orders of magnitude.
- Co-based carbides and nitrides are identified as promising plasma-active catalysts for energy-efficient hydrogen production.

## Abstract

Ammonia is a carbon-free hydrogen carrier, but its decomposition
typically requires high temperatures over costly Ru-based catalysts
due to the large barrier for NN bond formation. We develop
a multiscale framework combining density functional theory, zero-dimensional
plasma kinetics, and microkinetic modeling to elucidate how non-thermal
plasma (NTP) enables low-temperature NH3 decomposition
over Co-based carbides and nitrides, benchmarked against Ru and Co.
Under thermal conditions, all catalysts are limited by NN
bond formation, with Co3C­(001) most active owing to its
negatively charged surface, strong N* binding, and low activation
barriers of NN bond formation. Plasma-induced vibrational
excitation of NH3 and its reactive radicals promotes a
radical-driven •NH2–N* coupling pathway that
dominates on Co3C­(001) and Co3N­(001), shifting
the rate-limiting step to NH3
(v1) dissociation, increasing turnover frequencies by up to 6 orders
of magnitude, and reducing the temperature needed to reach a turnover
frequency of 5 s–1 from >680 °C (Ru and
Co
under thermal condition) to 267 °C (Co3C) and 415
°C (Co3N). These results identify Co-based carbides
and nitrides as promising plasma-active catalysts for energy-efficient
hydrogen production from ammonia.