Candle-soot template-mediated synthesis of nanoporous WO3 films as photoanodes for solar water splitting

Nanostructured WO 3 film photoanodes could achieve solar water splitting efficiently, through utilizing their structure advantages in light harvesting, carrier transfer, water molecules adsorption and dissociation. The establishment of suitable methods for the preparation of nanostructured WO 3 film photoanodes is highly essential for solar water splitting application. Herein, a facile candle-soot template-mediated method was developed to prepare nanoporous WO 3 films on FTO glass substrate. Through adjusting the solvent of precursor solution, the morphology of WO 3 films can be controlled optionally. Taken the resultant WO 3 films with different morphologies as photoanodes for solar water oxidation, higher activity, faster kinetics and better stability were achieved on the nanoporous WO 3 film photoanodes, relative to the dense-structure WO 3 film photoanodes. Among the resultant nanoporous WO 3 films, the optimal WO 3 (WO 3 -T/H 2 O+EtOH) film was prepared using a water/ethanol mixture as the precursor solution solvent. The water oxidation photocurrent of the WO 3 -T/H 2 O+EtOH film at 1. 23 V vs RHE was 0.39 mA/cm 2 , which was 3.5 times for the dense-structure WO 3 film photoanode. Meanwhile, the WO 3 -T/H 2 O+EtOH film photoanode had stable activity in sustained solar water oxidation reaction. Mechanism investigations revealed that the nanoporous WO 3 film photoanodes being of better water oxidation performance mainly ascribed to their nanostructure for harvesting more photons, easy achieving carrier transfer, beneficial water molecules adsorption and dehydrogenation oxidation.