Controllable synthesis of vertically aligned WO3 nanoplate arrays on stainless steel for improved visible-light photoelectrocatalytic activity†

Vertically aligned WO₃ nanoplate films were synthesized on stainless steel (SS) via a simple hydrothermal method. The prepared WO₃ films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Results of these analyses reveal that the SS surface was well-covered with compact and vertical WO₃ nanoplates with a monoclinic single-crystalline structure. The film obtained through a 2.5 h hydrothermal reaction exhibited excellent photoelectrochemical performance under visible-light illumination and generated an anodic photocurrent of 0.754 mA cm⁻² at 0.8 V (vs. Ag/AgCl). WO₃ photoelectrodes could degrade 98.9% of methylene blue (MB) within 120 min through a photoelectrocatalytic (PEC) process. The stability of the as-prepared photoelectrode was also studied, and no significant reduction in PEC activity was observed after recycling for 5 times. The supreme PEC activity of the aligned WO₃ nanoplate films can be attributed to the direct charge transport pathway in the 2D structure and the bias potential applied to reduce the recombination of photogenerated electron–hole pairs.