Work Function Studies of Carbon Nanospikes for Electrochemistry by UPS

Carbon nanospikes show excellent energy and selectivity for electrochemical conversion of CO₂ to ethanol¹ and N₂ to NH₃.² Reactivity is attributed to physical structure more than composition. A spike geometry concentrates the electric field, promoting local electroreduction of reaction molecules. Using UPS, we have measured the work function of carbon nanospikes transferred to vacuum after extraction from a N₂-saturated LiClO₄ electrolyte at a range of potentials. The work function exhibits a general decrease with increasing negative emersion potential. The decrease is not 1:1 eV/V to the applied potential, nor is it linear. This may reflect imperfect double layer retention during transfer through air and into vacuum. In most cases, UPS spectra were typical, with an obvious low-energy cutoff. However, for several samples, including the pristine nanospikes, two cutoffs appeared to exist, one suggesting a much lower work function. The nature of the low-energy cutoff and possible connection to the geometry will be discussed.

1. Y. Song, et al., ChemistrySelect 1 (19), 6055 (2016).
2. Y. Song, et al., Sci. Adv. 4 (4) (2018).