Surface states engineering carbon dots as multi-band light active sensitizers for ZnO nanowire array photoanode to boost solar water splitting

Abstract

Efficient capture of solar photons is crucial in photo-electrochemical (PEC) water splitting devices for converting solar energy to hydrogen as an energy-dense carrier. Herein, we first reported the unique multi-band light absorption character on carbon dots (CDs) with controllable surface states and built an efficient photoanode by bonding such CDs as favorable solar photosensitizers on one-dimensional (1D) ZnO nanorod arrays (NRAs) for the PEC solar-to-hydrogen (STH) conversion. The multi-transition models related to surface CO, and COH states with different energy levels were identified to dominate the CDs' multi-model optical absorption covering the full-range visible region in the solar spectrum, which renders an excellent advantage of CDs in serving as the solar photosensitizer for photoelectric systems. Moreover, the fabricated ZnO@CDs heterostructure photoanode with the functionalized CDs used to harvest solar photons along with subsequent charge separation at heterointerface and transport along 1D directional channels was demonstrated to boost the photocurrent output and the photoconversion efficiency for solar water splitting.