The synergistic role of the photosensitivity effect and extended space charge region in an inorganic–organic WO3/PANI photoanode for efficient PEC water splitting

Abstract

The predicaments of poor carrier separation and light absorption need to be overcome in order to maximize the preeminent performances of WO₃ in photoelectrochemical (PEC) water splitting. Hence, we firstly prepared a 2D WO₃/PANI core–shell hybrid heterojunction with high light absorption efficiency by a simple hydrothermal and photo-assisted electro-deposition method. A photocurrent density of 0.499 mA cm⁻² at 1.23 V vs. RHE is achieved by the as-prepared hybrid heterojunction, which is about 2.35 folds higher than that of bare WO₃ (0.212 mA cm⁻²). Moreover, the PEC stability is significantly enhanced to 87% from 60% with the deposition of organic PANI. PEC and optical measurements demonstrate that the significant PEC properties are attributed to improved photogenerated carrier separation efficiency (η_sep) and injection efficiency (η_inj) as well as broadened light absorption due to the synergistic action of the photosensitivity effect and extended space charge region (SCR), including a built-in electric field and depletion layer, in which the lifetime of photogenerated carriers is significantly improved with depletion layers of greater widths. This work can provide a favorable example for the development of more efficient hybrid photoanodes.