Etching treatment of vertical WO₃ nanoplates as a photoanode for enhanced photoelectrochemical performance

Vertically grown WO₃ nanoplates (WO₃NP) were successfully fabricated by a one-step hydrothermal process using citric acid as a structure directing agent. An innovative etching method was developed to obtain increased surface voids, active crystal facets and surface groups simultaneously, which led to a remarkably improved photocurrent density of ∼1.2 mA cm^-2 at 1.23 V vs. RHE, compared to 0.97 mA cm^-2 of pristine WO₃. Incident photon to current efficiency (IPCE) measurements also displayed a substantive increase of photoresponse in the intrinsic absorption range. Interestingly, a lower onset potential can be obtained after etching which is caused by the change of conduction and valence band positions. Moreover, the photoelectrocatalytic activity of WO₃ for degrading methylene blue (MB) was also evaluated. This effective design could provide a promising method to enhance the efficiency of photoelectrochemical performance based on WO₃ photoanodes.