Electrosprayed MnO2 on ZnO nanorods with atomic layer deposited TiO2 layer for photoelectrocatalytic water splitting

We have designed and produced a hierarchical photocatalyst for water splitting by first fabricating ZnO nanorods via a chemical bath deposition (CBD) process using ZnO seeds electrosprayed onto In-doped tin oxide (ITO), then electrospraying MnO2 particles as a co-catalyst, and finally depositing an ultrathin passivation layer of TiO2 via atomic layer deposition. These hierarchical photocatalysts exhibit excellent photoelectrochemical properties and reduced photocorrosion compared to materials without TiO2 coating. Moreover, the MnO2-garnished ZnO nanorods obtained at 550 °C deliver a 1.7-fold enhancement in photocurrent density (0.95 mA/cm2) at 1.2 VAg/AgCl in 0.5-M Na2SO3 solution compared to ZnO nanorods without MnO2. We attribute improved photocurrent density to rapid charge transfer and charge separation at the ZnO–MnO2 interface. This investigation illustrates a balanced design of a nanoarchitecture for photoelectrodes that favors formation of effective photoelectrocatalytic sites while improving stability for potential large-scale water splitting applications.