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 V_Ag/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.