Geometry-enhanced ultra-long TiO2 nanobelts in an all-vanadium photoelectrochemical cell for efficient storage of solar energy

Abstract Direct capture and storage of abundant but intermittent solar energy using storage devices are of paramount importance in development of sustainable energy, yet the daunting challenge is to enhance the conversion efficiency. Here we report an all-vanadium (all-V) photoelectrochemical storage cell (PESC) using geometry-enhanced ultra-long TiO 2 nanobelts (TNBs) to significantly improve solar energy storage efficiency. The TNBs are synthesized using a simple stirring-assisted hydrothermal method, where the stirring speed is adopted to effectively tune the geometry and structure of the TNBs. We demonstrate that highly efficient solar energy storage is realized by ultra-quick oxidization and reduction reaction of vanadium ions with, respectively, holes and electrons produced on the TNB surface. The obtained incident photon-to-current efficiency (IPCE) is ~22% at 350 nm without any external bias, double that of commercial P25 TiO 2 (~11%). The observed improved efficiency results from enhanced photoactivity and charge separation in the semiconductor, and mass transport of vanadium ions in the photoelectrode.