Seed layer-free hydrothermal synthesis of porous tungsten trioxide nanoflake arrays for photoelectrochemical water splitting

The simple preparation of efficient nano-photoanodes has been a key issue in the development of photoelectrochemical water splitting. In this work, a convenient and seed layer-free hydrothermal approach has been developed to synthesize vertically aligned porous WO(3) nanoflakes on a fluorine-doped tin oxide conductive glass substrate. The morphology of WO(3) nanoflakes could be manipulated by changing the annealing time, which further affected the performance of WO(3) nanoflakes as photoanodes. Under optimum conditions, the obtained photoanode can lead to a high photocurrent density of 2.34 mA cm(−2) at 1.4 V vs. Ag/AgCl under one sun irradiation (100 mW cm(−2)) and an incident photon to current conversion efficiency of 60% at 300 nm. The excellent photoelectrochemical performance can be mainly attributed to the larger active surface area, single crystal structure with an optimum thickness and the exposed highly active facets.