A facile one-step synthesis of single crystalline hierarchical WO3 with enhanced activity for photoelectrochemical solar water oxidation

Hierarchical architectures consisting of one-dimensional (1D) nanostructures are of great interest for potential use in energy and environmental applications in recent years. In this work, hierarchical tungsten oxide (WO3) has been synthesized via a straightforward, template-free, hydrothermal route from ammonium metatungstate hydrate and implemented in photoanode fabrication for solar water oxidation in photoelectrochemical cells and photocatalytic oxidation of organic pollutant. The flower-like WO3 micro-patterns are constructed by self-organized nanoscale length 1D building blocks, which are single-crystalline in nature, grown along (001) direction and confirm an orthorhombic crystal phase. Time-dependent experiments have been conducted to demonstrate their morphology evolution. The hierarchical architecture based photoanodes produce higher photocurrent (2-fold high) than the nanoparticles based photoanodes from solar water oxidation. The photon to current conversion efficiency achieved with the hierarchical architectures is 45% at 400 nm. The enhanced activity can be attributed to improved charge-separation by superior charge transportation through single-crystalline 1D building blocks.