Dissociative Mechanism from NH3 and CH4 on Ni-Doped Graphene: Tuning Electronic and Optical Properties

TL;DR

This study uses multi-scale computational modeling to explore how Ni-doped graphene can enhance hydrogen production and gas sensing by facilitating dissociation of NH3 and CH4 molecules.

Contribution

It introduces a combined DFT and SCC-DFTB approach to analyze dissociation mechanisms on Ni-doped graphene, revealing its potential for catalysis and gas separation.

Findings

Ni-doped graphene improves hydrogen transmission during gas interactions.

Methane and ammonia adsorb at different sites on graphene, affecting dissociation.

Ni-doped graphene outperforms pristine graphene in gas separation and sensing applications.

Abstract

In this study, we employ a multi-scale computational modeling approach, combining density functional theory (DFT) and self-consistent charge density functional tight binding (SCC-DFTB), to investigate hydrogen (H2) production and dissociation mechanisms from ammonia (NH3) and methane (CH4) on pristine and nickel-doped graphene. These two-dimensional materials hold significant potential for applications in advanced gas sensing and catalysis. Our analysis reveals that Ni-doped graphene, validated through work function calculations, is a promising material for gas separation and hydrogen production. The samples with adsorbed molecules are characterized by calculating chemical potential, chemical hardness, electronegativity, electrophilicity, vibrational frequencies, adsorbtion and Gibbs energies by DFT calculations. Methane molecules preferentially adsorb at the hexagonal ring centers of graphene, while ammonia inter-acts more strongly with carbon atoms, highlighting distinct molecular doping mechanisms for CH4 and NH3. Dynamic simulations show that CH4 splits into CH3+H, with Ni-doped graphene facilitating enhanced hydrogen transmission, while NH3 dissociates into NH2+H, which may lead to N2H4 formation. Our non-equilibrium Green's function (NEGF) simulations demonstrate increased H-atom transmission on Ni-doped graphene during gas interactions. These findings suggest that Ni-doped graphene is superior to pristine graphene for applications in gas separation, hydrogen production, and high-sensitivity sensors.