Hydrogen Atoms on Zigzag Graphene Nanoribbons: Chemistry and Magnetism Meet at the Edge

TL;DR

This study reveals how hydrogen atoms interact with zigzag graphene nanoribbons, demonstrating that edge magnetism influences chemical reactivity and that hydrogen chemisorption affects the magnetic properties, highlighting a complex interplay between chemistry and magnetism.

Contribution

It provides the first detailed analysis of how hydrogen adsorption affects and is affected by the edge magnetism in zigzag graphene nanoribbons.

Findings

Hydrogenation occurs preferentially at the edges due to site-dependent reactivity.

Chemisorbed hydrogen acts as a spin-1/2 paramagnetic center.

Hydrogen adsorption influences the magnetic and electronic properties of ZGNRs.

Abstract

Although the unconventional $\pi$-magnetism at the zigzag edges of graphene holds promise for a wide array of applications, whether and to what degree it plays a role in their chemistry remains poorly understood. Here, we investigate the addition of a hydrogen atom $-$ the simplest yet the most experimentally relevant adsorbate $-$ to zigzag graphene nanoribbons (ZGNRs). We show that the $\pi$-magnetism governs the chemistry of ZGNRs, giving rise to a site-dependent reactivity of the carbon atoms and driving the hydrogenation process to the nanoribbon edges. Conversely, the chemisorbed hydrogen atom governs the $\pi$-magnetism of ZGNRs, acting as a spin-$\frac{1}{2}$ paramagnetic center in the otherwise antiferromagnetic ground state and spin-polarizing the charge carriers at the band extrema. Our findings establish a comprehensive picture of the peculiar interplay between chemistry and magnetism that emerges at the zigzag edges of graphene.