N-N type core-shell heterojunction engineering with MoO3 over ZnO nanorod cores for enhanced solar energy harvesting application in a photoelectrochemical cell

Herein, we report an easy and scalable chemical bath deposition and spin coating route of n-n hetero-architecture engineering to fabricate MoO3-ZnO core-shell nanorods (NRs) based photoanode, which is indeed the first time demonstration of this particular nano-heterojunction for solar energy conversion and hydrogen energy generation in a photoelectrochemical (PEC) cell. We further tune the MoO3 shell thickness by varying spin coated layer thickness. An average thickness ∼100 nm of MoO3over 450 nm ZnO NRs significantly improves the photocurrent from 3.3 to 27.6μAcm−2. A 7.5 fold increase in applied bias photon to current conversion efficiency (ABPE) value is achieved upon visible light illumination (Visible light, 10 mWcm−2) with a maximum value of 0.15% than bare ZnO NRs (0.02%). In addition, hydrogen gas (5 μmolcm−2) is evolved even at no external potential applied to the PEC cell with this MoO3-ZnO. The physical insight of the enhanced PEC performance is also elucidated. We find the n-n hetero-architecture to provide a suitable solution to maximize solar light absorption along with enhanced charge carrier separation which also boosts the charge transportation and mobility in the junction region due to suitable core-shell interfacial band alignment and modulation of interfacial electronic structure. Mainly, the MoO3 shell provides a potential solution to get more catalytically active sites and the outer Mo-O dipole layer transfers holes to the electrolyte for easy oxidation of water.