Effect of alkane adsorption on the electrochemical properties of graphene†

The surface characteristics of graphene, such as hydrophilicity and adsorptivity, have clear impact on the surface charged state and the transport of electrons. Recent studies have shown that alkane molecules are readily adsorbed on graphene surfaces exposed to air, decreasing its hydrophilicity. Consequently, it raises a question of the effects of the adsorbed alkane on the electrochemical properties of graphene. In this study, ab initio molecular dynamics simulation combined with machine learning is used to investigate the adsorption behavior of alkane molecules on the graphene surface and the impact of alkane molecules on the electrical double-layer structure. It is found that longer-chain alkane molecules have greater adsorption energy, and the alkane molecules adsorbed on the graphene surface cause the equilibrium position of Na⁺ to move farther away from the graphene surface and alter the distribution of interfacial water that is unfavorable for hydrogen evolution reaction. This leads to the reduction of the graphene electrode capacitance and the widening of the voltage window, which is consistent with our experimental results in this study. This study emphasizes the impact of alkane molecules on the electrochemical properties of graphene and the importance of surface treatment.