Effects of Field Strength and Silver Nanowire Size on Plasmon-Enhanced N₂ Dissociation

Abstract

Dissociation of the nitrogen molecule via plasmon-enhanced catalysis using noble metal nanoparticles has been investigated both experimentally and computationally in recent years. However, the mechanism of plasmon-enhanced nitrogen dissociation is still not very clear. In this work, we apply theoretical approaches to examine the dissociation of a nitrogen molecule on atomically thin Ag n nanowires (n = 6, 8, 10, 12) and a Ag19 + nanorod. Ehrenfest dynamics provides information about the motion of nuclei during the dynamics process and real-time TDDFT calculations show the electronic transitions and population of electrons over the first 10 s of fs time scale. The activation and dissociation of nitrogen are typically enhanced when the electric field strength increases. However, the enhancement is not always monotonic with field strength. As the length of the Ag wire increases, nitrogen is typically easier to dissociate and thus requires lower field strengths, even though the plasmon frequency is lower. The Ag19 + nanorod leads to faster dissociation of N2 than the atomically thin nanowires. Overall, our detailed study yields insights into the mechanisms involved in plasmon-enhanced N2 dissociation, as well as provides information about factors that can be used to improve adsorbate activation.

Effects of Nanowire Doping on Plasmon-Enhanced N2 Dissociation

“…Longitudinal excitations occur in the range of 1–2 eV, and transverse excitations occur in the range of 4–6 eV. According to previous results, the longitudinal excitation energy for the undoped Ag 6 N 2 system is 1.88 eV; HOMO → LUMO and HOMO–1 → LUMO+1 are involved in the longitudinal excitation, with the HOMO → LUMO transition being dominant . For the Ag 6 NiN 2 doped system, the longitudinal excitation energy is 1.68 eV.…”

“…According to previous results, the longitudinal excitation energy for the undoped Ag 6 N 2 system is 1.88 eV; HOMO → LUMO and HOMO−1 → LUMO+1 are involved in the longitudinal excitation, with the HOMO → LUMO transition being dominant. 41 For the Ag 6 NiN 2 doped system, the longitudinal excitation energy is 1.68 eV. HOMO → LUMO, HOMO−1 → LUMO+1, HOMO−4 → LUMO, and HOMO−4 → LUMO+1 transitions are involved in the longitudinal excitation, and again, the HOMO → LUMO transition has the greatest weight in the excited state.…”

“…A single Ehrenfest trajectory is performed for all simulations; because the initial velocities are zero, sampling is not expected to change these results. It should be noted that Ehrenfest dynamics is a mean-field approach, and several issues such as lack of detailed balance can arise because the dynamics take place on an average potential surface. , Although most studies of plasmon-enhanced catalysis have employed Ehrenfest dynamics, − , some researchers have examined individual ground and excited state potential energy surfaces or have employed other approaches such as surface hopping in order to investigate the importance of these surfaces.…”

“…The effects of doping on the plasmonic resonance characters of silver and gold nanochains have been studied using TDDFT, and previous work showed that the metal atom dopants can lead to additional electronic excitation modes in the absorption spectrum, which will then enhance the collective excitations. ,, Compared with the previous studies, our work will be more focused on how doping affects plasmon-enhanced N 2 dissociation. To study the nuclear motions in excited states, various types of nonadiabatic quantum dynamics have been applied to examine the photocatalyzed process such as small molecule activation/dissociation. − In this work, we applied mean-field Ehrenfest dynamics − to watch the evolution of N 2 when interacting with a doped plasmonic silver nanowire.…”

Connectivity between Static Field and Continuous Wave Field Effects on Excitation-Induced H2 Activation

“…Though this is a higher field strength than most experimental CW fields, this compensates in part for the short duration of the field application. Moreover, previous work has shown that smaller nanoclusters typically require stronger applied fields for adsorbate activation, but this decreases with increasing cluster size. , For RT-TDDFT calculations, the electronic step is set to 0.002 fs. For the Ehrenfest dynamics, the electronic step size is 0.00025 fs and the nuclear step size is 0.1 fs, and the initial velocity of all the systems is set as zero.…”