Vertical graphene nano-antennas for solar-to-hydrogen energy conversion

Xu, C., Bo, Z., Wu, S., Wen, Z., Chen, J., Luo, T., Lee, E., Xiong, G., Amal, R., Wee, A., Yan, J., Cen, K., Fisher, T., Ostrikov, K.
Solar Energy

Abstract

Effective separation and transfer of photogenerated charge carriers are common issues in solar energy conversion. Strong localized electric fields near functional nanostructures reduce charge recombination and boost energy efficiency and photocatalytic activity. However, common metal-based photocatalytic systems on conducting supports under-utilize infrared (IR) light energy, and suffer from unsatisfactory interface quality and stability, as well as high complexity and cost. Here we develop a photocatalytic nano-antennas simultaneously featuring localized field-enhancement in IR, high electric conductivity, and interface stability. In the nano-antennas, plasma-made all-carbon vertical graphene nanopetals (GPs) are covalently interfaced with high-performance metal-free semiconducting graphitic carbon nitride (g-C3N4) photocatalyst. The photo-induced force microscopy is used to obtain real-space images of localized electric field enhancement in the near-IR and mid-IR ranges along the vertically standing ultra-sharp GP edge nano-antennas. The photocurrent, electrochemical impedance spectra, and time-resolved photoluminescence spectra confirm that the GP edge nano-antennas significantly enhance the photogenerated charge carrier separation, accelerate carrier migration, and prolong carrier lifetime. We also demonstrate the scalability of production of the petal edge nano-antennas. The unique graphene nanoarchitecture offer exotic spectral properties, which are essential for many large-scale solar energy harvesting applications such as photocatalysis, photovoltaics, and solar-thermal water desalination and purification.

DOI: 10.1016/j.solener.2020.07.069