Three-dimensional core-shell heterostructure of tungsten trioxide/bismuth molybdate/cobalt phosphate for enhanced photoelectrochemical water splitting.

Hydrogen has attracted increasing attention as clean energy for fuel cells over the past decade. Photoelectrochemical (PEC) water splitting is considered the most feasible production method but its practical efficiency depends significantly on the photogeneration rate of electron (e) and hole (h) on a semiconductor photoanode and the rapid separation of these charge carriers. A proper match of small and large bandgap positions is also necessary. This paper presents a three-dimensional core-shell heterostructured tungsten trioxide/bismuth molybdate/cobalt phosphate (WO/BiMoO/Co-Pi) photocatalyst synthesized using simultaneous hydrothermal and electrodeposition techniques. Uniform BiMoO nanoflakes formed on WO nanoplates as evidenced by various micro-spectroscopic techniques. The as-prepared WO/BiMoO/Co-Pi hetero-photocatalyst exhibited significantly high photoelectrochemical activity, where its photocurrent efficiency was 4.6 times greater than that of the constituent WO Such drastic improvement in the PEC properties can be corroborated by the appropriate bandgap alignment among WO, BiMoO, and Co-Pi, resulting in a sufficient charge carrier density with efficient, fast charge-transport complementing their structural-morphological synergy. Furthermore, a heterojunction charge-transfer mechanism was proposed to verify the role of the co-catalyst, Co-Pi, in enhancing the photocurrent at the WO/BiMoO photoanode under the same applied bias.